Signs of Summer 7: Earwigs!

photo by Niels Heldenreich Flcikr

photo by Niels Heldenreich Flickr

Everyone should go outside and pick up one of the potted plants on your porch or deck. It is almost certain that under some (or all) of these plant pots will be creatures that are nobody’s favorite insect: European earwigs!

The European earwig (Forficula auricularia) is a native, insect species of Europe, Northern Africa and Western Asia that has been accidentally introduced into a number of temperate and tropical countries around the world. Its first recorded appearance in the United States was in Seattle, Washington in 1907. It was likely brought to this country in a shipment of flowers, fruit, or vegetables. In the hundred years since it arrived in the United States, the European earwig has found its way to almost every region and every state in the country.

There are twenty-two species of earwigs in the United States. Twelve of these species (like the European earwig) are alien exotics, and ten are endemic (“native”). Only four of these twenty-two species, though, are classified as pest (or potential pest) species. Most of the earwig species in the United States actually are quite beneficial acting as shredders and comminuters in the soil decomposer community and as biological control agents (predators) for a variety of insect pests. The European earwig is classified as a pest species, but it is also acknowledged that it can also be an active predator of crop damaging aphids, caterpillars, beetles, and midges. Its role as a pest controlling agent is especially important in organic orchards and farms. In Pennsylvania, the European earwig is the most commonly found “pest” earwig species.

The name “earwig” has a long and extremely non-scientific history. It is derived, according to the Oxford English Dictionary (and who could argue with that?), from the Old English word “earwicga” which translates as “ear wiggler.” There is an ancient myth that these very harmless (to humans, anyway) insects have the ability to crawl up the ear canal of a human and then eat their way into that unfortunate person’s brain. None of this is true, and it is very unclear why anyone would have thought that it was or why this myth would persist over many hundreds or thousands of years! There have been, though, some interesting fictional adaptations of “earwicga” myth in literature and in science fiction television shows and movies.

The European earwig is a little over one half an inch long (females are larger than males). They have a dark, red-brown body, a reddish head, yellowish legs, two long antennae, two membranous flight wings (which it seldom uses) tucked under the hard, protective forewings, and two very distinctive cerci (“pinchers”) on the end of its abdomen. The shape of the cerci differs in males and females with females having straight cerci and males having curved cerci. These cerci are used to grab and secure prey and also, in males, as weapons in mating competitions.

European earwigs are nocturnal and spend the day in dark, moist places (like spaces under rocks, logs, surface vegetation, flower pots, leaf litter etc.). One frequently mentioned method of bio-control of earwigs is to make sure that your property is free of these potential daylight refuges. Earwigs are omnivorous and will consume plant materials (both living and dead), aphids, spiders, insects, insect eggs. They will consume garden plants and a wide variety of fruit and vegetable crops but, very interestingly, seem to do so when potential prey (like aphids) are not present in sufficient numbers. European earwigs also accumulate inside human habitations and can work their way into almost any open space or crevice. They can consume stored food products (flour, bread, cereal, crackers, etc.) and befoul clothes, books, laundry and more with their odiferous secretions.

European earwigs are solitary organisms and have no social behaviors or communication systems. Males and females meet up once a year, though, in order to mate. Males find females via pheromones that the females excrete in their feces. Males attracted to the pheromone then compete with each other for the attention of the female. It is thought that body size and especially cerci size are the critical variable in a male’s reproductive success. Mating takes place in early autumn.

Photo by Tom Oates Wikimedia Commons

Photo by Tom Oates Wikimedia Commons

The female then digs out a brood nest and lays her clutch of thirty to fifty eggs. This nest will also serve as the hibernation nest for the female and also for the male. The female will tend to the eggs stacking them up and then spreading them out making sure that fungi do not grow on them and protecting them from possible predators. The eggs will hatch in the spring and the first nymphs that emerge (the first “instar”) will remain in the nest and continue to be cared for by the female. The female guards and feeds the nymphs (via regurgitated plant materials) throughout the first instar stage (which is about the first month of life). This level of maternal involvement with offspring is very unusual in insects!
There are four nymphal stages in earwigs. In the second instar stage the female opens up the nest and the nymphs begin to go out at night to search for food. These second instars, though, tend to (or at least try to) return to the nest during the day. By the third instar stage, though, the nymphs have completely left the nest and move freely about the soil and litter habitat searching for food by night and seek out their own daylight refuges by day. These nymphs develop into adults in the late summer or early fall and then mating occurs and the cycle begins all over again.

Some female earwigs lay a second clutch of eggs after the second instar nymphs have left the nest. This second batch of eggs hatches and marches through the four nymphal stages very rapidly in the warm temperatures of summer and matures into adult earwigs at the same time as the cohort that hatched from the overwintering clutch of eggs.

Earwigs are preyed upon by many species of birds (including chickadees and nuthatches) and are also eaten by a number of amphibians (especially toads). They are also parasitized by the parasitoid fly Bigonicheta spinopennis and susceptible to numerous bacterial and fungal infections.

So, when you turn up a few earwigs in a flower pot or under a rock or log, try not to be completely grossed out! I think that I have received over the years more phone calls and emails about earwigs (“What are they?” “What do they do?” “Are they from outer space?”) than about any other insect (except maybe for brown, marmorated stink bugs). These insects may be doing a great deal of good out in their soil and litter ecosystems, and they are some of the most devoted and attentive mothers in all of Class Insecta! Let’s give them a little respect, at least.

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Signs of Summer 6: Milkweed and Monarchs

Female Monarch (photo by K.D.Harrelson (Wikimedia Commons))

Female Monarch (photo by K.D.Harrelson (Wikimedia Commons))

Last year I wrote about the importance of milkweed to the biology of the monarch butterfly. Various species of milkweed are the only plants on which the monarch can lay its eggs.  The chemicals that the monarch caterpillar accumulates from feeding on the milkweed make it and also the adult butterfly it will turn into poisonous to, and thus protected from, most potential vertebrate predators. Human impacts on old field ecosystems where milkweeds can flourish are greatly reducing the distribution of this important plant and are at least one of the factors that are causing the observed population declines of this beautiful butterfly.

Over the past twenty-five years both out on the campus nature trail and also around my house I have tried to encourage the growth of milkweed. I have opened ripe milkweed seed pods and let the fluffy, floating seeds drop into the butterfly garden and succession plots that are located on the entrance edge of the nature trail. I have not subsequently, however, observed any thriving milkweed plants in these plots! The USDA describes milkweed propagation as an easy task. I have not experienced the ease of it!

My best ‘gardening” of milkweed has come around my house. Whenever I see a milkweed plant I let it grow. This has led to some discussion about the aesthetics of several of our flower beds, but playing the “monarch card” usually results in allowing the milkweed to remain. One incredibly persistent set of milkweed plants comes up through a crack in my driveway. They have been growing, flowering and thriving for at least fifteen years!
Just outside my back room where my writing desk is located there is a stand of nine very hearty milkweed plants. They started flowering a week and a half ago and have been absolutely covered with honey bees and bumble bees. I can hear their buzzing as I sit at my desk!

I mentioned last year that in spite of the presence of milkweed around my house, I have yet to see significant numbers of monarchs and have yet to observe any monarch caterpillars munching away on the milkweed leaves. I did see a monarch fluttering around the milkweed last week, though, and I have been watching the plants closely for any signs of eggs or caterpillars.

The life cycle of the monarch can be examined from two different perspectives: the local cycle of an individual and the year-long cycle of the migrating population. The local cycle typically takes six to eight weeks from egg to senescing adult, while the migrating cycle may extend the life span of an individual to up to nine months.

The local cycle begins with the adult butterflies emerging from their cocoons (their “chrysalises”). These adult may live for two to five weeks depending on temperature and other weather conditions and also on the availability of their food supply (flower nectar). The emerged females release pheromones which attract males. Females that have not mated release more pheromones than previously mated females and, thus, attract more males. Males fly after the females and force them to the ground to mate. Only about one third of these mating attempts, though, actually result in the transfer of the male’s packet of sperm (the “spermatophore”).

Monarch caterpillar (photo by D. Ramsey (Wikimedia Commons))

Monarch caterpillar (photo by D. Ramsey (Wikimedia Commons))

Females lay their eggs on the leaves of milkweed plants. A female can lay a total of three hundred to four hundred eggs and will spread these eggs over many milkweed plants. The eggs hatch in three to five days depending on the temperature. The emerging larvae feed first on the egg capsule and then begin to eat the milkweed leaves. They molt five times during this larval life stage and increase their body mass more than two thousand times. The eggs and the larvae (the “caterpillars”) are under intense predation pressure. More than ninety percent of the eggs and caterpillars will fail to survive. Eggs are eaten by ants, earwigs and snails, and larvae are eaten by beetles and other insects (like paper wasps) or killed by parasitoid wasps, bacteria, or fungi. Since the larvae are feeding exclusively on milkweed leaves they are accumulating the milkweed’s cardenolides (a cardiac glycoside that can cause the heart of a vertebrate to stop its contractions) in their body tissues. These cardenolides make the larvae (and, eventually, the adults, too!) poisonous to most vertebrates. Relatively few monarch caterpillars or adult butterflies, then, are consumed by vertebrate predators.

The end stage caterpillar then forms a cocoon (“chrysalis”) within which the tissues and organs of the larvae dissolve and are reformed into the structures of the butterfly. This metamorphosis takes between nine and fifteen days. The emergence of the butterfly from the chrysalis then starts the cycle all over again.

In the migrating life cycle there are great differences in life span and timing of reproduction especially in the Fall migrating forms. This migrating life form does not mate when it emerges from its chrysalis, instead it begins its long flight toward its frequently far distant over-wintering habitats. In these particular habitats (described below) the migrating life form enters a hibernating condition called “diapause” which can last many weeks or even months. Emergence from this diapause state then triggers mating and the beginning of the return migration back to the Spring and Summer ranges. These migrating monarchs may live up to nine months but spend much of this time period in its inactive, diapause state.

Monarchs overwintering in Mexico (Bfpage (En. Wikipedia))

Monarchs overwintering in Mexico (Bfpage (En. Wikipedia))

The two migrating populations of monarchs in North America are separated by the Rocky Mountains. The larger area east of the Rockies supports a much larger population of monarchs. All of these butterflies overwinter in the coniferous forests in the mountains of the Mexican states of Michoacán and Mexico. For the monarchs that reach the northeast states of the United States and the southeast provinces of Canada, this migration to and from this very specific overwintering site in Mexico covers several thousand miles. The monarchs that live in the smaller area west of the Rockies, on the other hand, overwinter in in coastal sites in Southern and Central California. Their migratory route only measures hundreds of miles at the most. In both overwintering sites, however, the numbers of monarchs covering the trees and shrubs while waiting out the winter months in their diapause states can be truly staggering!

Following the eastern population through their cycle blends together the local and the migratory aspects of the monarch’s life cycle. Between February and March the monarchs who have spent possibly four or five months in their diapause state, re-awaken, mate, and then begin their flight north. They fly as far north as Texas and Oklahoma and out across the southern states. With luck, they have timed their arrival in these areas with the emergence of the new, Spring crop of milkweed. The overwintering migrants then lay their eggs on the milkweed and die. The next generation then undergoes a local life cycle and the adult butterflies mate on emergence and then continue their fight northward in late March and early April. This cohort of adults then gets further north into the Midwest and mid-Atlantic states. This cohort again has ideally timed their northernmost arrival to the emergence of the new crop of milkweed. This first, post-migrant generation then lays their eggs on the milkweed and dies. The second post-migrant generation then undergoes a local life cycle sequence and the emerging adults in June or July head into the northern most states and southern Canada. Again, they lay their eggs near the end of their brief lives and die. The next generation (the third, post-migrant generation) can have two different types of individuals. One type continues on its collective northern flight while the other type turns to the south and gets a head start on the Fall return migration. The northward flying cohort lays its eggs on the northern edge of the milkweed plants while the southward flying cohort lays its eggs on the southern mass of milkweed. Out of these eggs are hatched the larvae that metamorphose into the adults that will be the long-lived migratory life forms that will then attempt to fly all the way back to the coniferous forests in the mountains of Mexico.

The migrating monarchs stop at nectar sites to drink and re-fuel. They follow a variety of cues to stay on their course including polarized light patterns, UV light patterns and the Earth’s geomagnetic fields. They also utilize weather fronts and prevailing winds to give them a flight boost and save a great deal of wear and tear on their delicate wings.
The monarch I saw on my milkweed was probably part of the third, post-migrant generation cohort. He (and he did look like a male) was probably looking for a female with which to mate and then would either fly off to the north or turn back to the south. His offspring will be the long distance migrators that will make the long trek back to Mexico.

We will see more monarchs over the next two months. Let’s keep planting and conserving milkweed (and as many natural nectar sources as possible!) so that they can sustain themselves on their long extended cycles!

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Signs of Summer 5: Several Snakes and a Slug

In the abundant growth of the grasses and weeds that we call our “lawns” there are all sorts of unexpected discoveries working their way through the stems and thatch. The ones without legs are particularly notable.

John Mizel Flickr

John Mizel Flickr

This summer black rat snakes have been extremely abundant. Down on the Roaring Run Trail, where I ride my bike a couple of times a week, I have had to frequently stop to let three and four foot long black rat snakes make their open slither across the trail from one mowed grass area to the next. There is no pattern as to whether the snakes are heading toward the riverside of the trail or away from it, and no particular time of day at which I see them, but I always stop if there is a snake crossing the trail so that I can direct other bikers and hikers away from it for fear they might accidentally run over or step on the snake. About a month ago, I came upon a group of five walkers clustered together on the trail, talking nervously. There was a black snake in their path and they were afraid to get close to it. I prodded the snake to hurry it along on its way across the trail, and they thanked me for helping them out (and, I am sure, for not making fun of them!). About a half an hour later on my return ride back to the parking lot, the same five walkers were once again stopped in their tracks by a different black snake. The snake seemed to enjoy being the object of the rapt attention of all of those people and did not seem to be in any hurry to get off the trail!

The black rat snake is one the more impressive animals found in the biotic community of Western Pennsylvania. Individuals of this species may reach lengths of 7 to 8 feet and is, thus, the longest snake naturally occurring over its broad, geographic range of the eastern United States (west to Wisconsin and parts of Texas) and southern Ontario. Most typically the dorsum (back) of this species is solid black and the venter (belly) is gray along most of its body length. The gray belly coloration changes into a solid white at the throat. There may also be a series of white spots and speckles running along its sides. There are, however, numerous color variants of this species, and individuals who are gray and even yellow are frequently found. These snakes are very important rodent predators and help to keep our natural ecosystems (and our barns and garages and yards) if not rodent free, then in a rodent balanced state.

A black rat snakeA black rat snake with whom I had a long and close relationship was “Strobe” a yellow/brown color variant black rat snake (image, left, D. Sillman). I found Strobe as a tiny, newly hatched snake slithering his way down the lower hallway of the Science Building at Penn State New Kensington. My son, Joe, had expressed interest in have a snake for a pet, so this seemed an excellent opportunity to fill that pet niche for our family. I collected Strobe in a large, Erlenmeyer flask and after a visit to a local pet store, took the “free” snake home with about a hundred dollars of pet snake equipment (habitat, heater, etc.). Joe took excellent care of Strobe for the next six years, and Strobe grew into a very impressive, three foot long, gold-colored, black rat snake. We did learn something very important as we raised Strobe, though: black rat snakes do not make good pets. He never became anywhere close to being tame and would, if an opportunity arose, escape from his expensive habitat box (and hide in the most obscure places of the house (Deborah REALLY loved that!)). He would also grab onto and constrict down on any hands and arms trying to move or feed him and bite those said hands and arms with all of the force he could muster. Now black rat snakes are not poisonous, but they produce an anticoagulant in their saliva that can allow the tiny puncture holes made by their teeth to bleed volumes way out of proportion to the size or depth of the wound!

A biology colleague over in Eastern Pennsylvania heard about Strobe and, since he was interested in the genetics of this non-black coloration of a black rat snake, offered to trade Joe a ball python named “Julius” (which was short for “Julius Squeezer”) for Strobe. Joe accepted and we then had several more, great snake years with the gentle, sweet, very appropriate pet snake, Julius.

Several years ago Jason Bush (our campus’ Director of Business and Finance) and I were out on the Campus Nature Trail looking for two metal surveying plates that marked the boundaries of the campus. I was off the trail on my hands and knees shifting through leaf litter looking for one of the plates when I saw a large diameter black rat snake gliding by. I could only see part of the snake (the rest was hidden in the leaves and ground vegetation), but as I watched the head and the first part of the body slide past I shouted to Jason “I got a three foot black snake down here …. no, it’s more like four feet … no, five … no, more like six!” It was a six and half foot black rat snake with several large bulges in its body which, I am sure, represented recently ingested rodents.

We never did find that plate, by the way!

D. DeStefano

D. DeStefano

About a month ago I got an email from Danielle DeStefano, whom most of you know as our campus’ Assistant Director of Admissions, but to me she will always be a biology student who has temporally strayed off the path of Truth! Anyway, Danielle sent me an email with an attached photograph of something she saw coming through the grass and across the sidewalk on her way into her office. The photograph is reproduced to the left.
This beauty is a leopard slug (Limax maximus) who was on his way from his nighttime prowling around looking for food to his daylight, sleeping hideout. Leopard slugs are big! They can be four to eight inches long and have gray to brownish-yellow bodies with “leopard-like” streaks of black. They are natives of Europe and have been accidentally transported to places colonized by Europeans (including North and South America, South Africa, Australia, and New Zealand). They are also almost always found near people and their habitations! They mostly eat dead plant materials but can also dine on carrion, fungi, and other slugs. They can also consume young, just sprouting crop plants almost as fast as they can grow! For this reason they are often classified as an agricultural pest.

Leopard slugs can live two and half to three years, and they tend to live alone rather in groups (or in whatever we might call a herd of slugs!). They are hermaphroditic (i.e. have both male and female reproductive organs) but reproduce sexually via some very interesting mating behaviors. A fertilized leopard slug can lay hundreds of eggs (so their population is capable of very rapid growth!).

Great find, Danielle! Keep your eyes on the ground!

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Signs of Summer 4: Two Birds

Pierre Selim Wikimedia Commons

Pierre Selim Wikimedia Commons

I have spent most of today looking out my back window and watching all sorts of bird behaviors. The chickadees have been hunting and gleaning up and down the spruce branches, the male mourning doves have been following the females on their head-jerking walks around the yard obviously ready to start the second clutch of the season, and the blue jays have been laying themselves flat on the hot concrete of the basketball court, spreading out their wing and tail feathers to cook out some of their lice and mites. The robins have been hunting for worms over on the shady lawn, and the chipping sparrows are pecking at (to me) invisible tidbits on both the grass and the sidewalk. The activity of all of these different species seems almost orchestrated. Each bird moves through its section of the habitat looking for its type of food and none of them seem to interfere with the others.

Joe Ravi Wikimedia Commons

Joe Ravi Wikimedia Commons

But then two birds arrive that disrupt the harmony of this ecological dance: European starlings (pictured above) and English sparrows (pictured to the left).

Both of these species were brought to North America back in the Nineteenth Century. The starlings have a very definite place and time of introduction: Central Park in New York City in 1890. The person who released these sixty (or sometimes reported to have been one hundred) starlings was Eugene Schieffelin, and his intention, as president of the “American Acclimatization Society,” was to introduce into North America all of the bird species mentioned in the works of William Shakespeare. So, because in “Henry IV, Part 1” Hotspur plots to have a trained starling saying the name “Mortimer” over and over to Henry with the intent of driving him mad, we got these sixty (or one hundred) starlings that then spread all across the continent and now number between two hundred million to seven hundred and fifty million individuals! They also cause eight hundred million dollars in agricultural crop damage each year and via spreading disease among cattle and pigs in feed lots probably that much again in damage to meat production. Almost two million starlings are killed each year via various pest control procedures, but as one control agent put it, the effectiveness of these control measures are “like trying to bail the ocean with a thimble.”

Thanks, Eugene.

There is a flock of fifty to one hundred starlings that roosts down the street. They cover the lawns and fields between their roost and my house, and they fill up the branches of my neighbor’s locust trees, but they seldom come into my yard. When they do swoop in the other bird species scatter and the ecological dance collapses.

Starlings are very aggressive “secondary cavity” nesters. They seek out sheltered nesting sites and evict any bird that might have been in possession of the site. This disruption of the nesting behaviors of other bird species (and the starling’s predilection to eat both eggs and nestlings of those other bird species) along with the starling’s dominant behaviors in their feeding habitats (they are quite omnivorous and will eat invertebrates, small vertebrates, seeds, and fruits … anything that is available!) have been a significant factor in the overall decline of song bird populations in North America.

There is a group that denies any of this is going on. These starling-apologists feel that it is a media-led witch hunt that has led to the bad image of this species. Even a casual reading of “Starling Central’s” web site, though, makes it very clear that their assertions are based on carefully assembled and edited facts.

I want to say some nice things about starlings, though. They sing beautifully and with a wide range of original and imitated songs. They can even be taught to speak (you could teach one to say “Mortimer” over and over!). They have beautiful, iridescent, black feathers that initially form with white tips (making the bird look spotted right after its molt), but the tips wear down and leave the shiny black plumage in its place. The very name “starling” refers to their star-like appearance in flight: a sharp pointed beak, two pointed wings, and a short, pointed tail.

Now many people really do hate starlings, but the level of antipathy to them is nothing compared to the rage of true lovers of nature that is directed at English sparrows. There was an article in the New York Times this spring in which the writer described the behavior of her mother, a kind and gentle woman who loved birds dearly, and her on-going vendetta against English sparrows (there was a scene at a birthday party in which a sack of caught sparrows were gassed in auto exhaust that was particularly ghastly).

English sparrows (also called “house sparrows”) have a murkier North American origin than starlings. Again in the late Nineteenth Century there was an active program in many cities across the country to import and establish this species. Various reasons are given for this: it was thought that the sparrows would eat insect pests. It was thought that they would peck grains out of horse manure (a big pollution problem on city streets!) and accelerate its decomposition. There is also some reference to people simply liking sparrows and wanting them around them! And, our old friends of the American Acclimatization Society also cited “Hamlet” Act 5, Scene 2 with Hamlet saying “There is special providence in the fall of a sparrow,” and used it to justify bringing hundreds of birds over to the States. So from its multiple points of introduction, the English sparrow now numbers a hundred to a hundred and fifty million individuals in North America (There are five hundred and forty million individuals world-wide, and they are found on every continent except Antarctica!).

Why are English sparrows so hated? They are very aggressive toward other bird species (a list of seventy different types of birds that are attacked by English sparrows was posted on one web site), they evict other birds from their nests and destroy their eggs or kill their nestlings, and they very aggressively compete for food at a wide range of potential feeding sites and habitats. They also form large colonies in close association with people and even frequently flock with starlings! Their interactions with eastern bluebirds (which include forcing the bluebirds out of their tree hole nesting sites and human-made nesting boxes and the killing of bluebird nestlings) have in particular energized many in the birding community to wage all-out war on these sparrows.

But, English sparrows are not evil. They do suffer from being way too successful in their introduced ranges, and they have a great ability to thrive on the wastes of human society (they are the “French fry” bird around every fast food restaurant in the United States!), but they still have many characteristics that are admirable and worthy of note. The Humane Society of the United States has a long web page dedicated to consideration of the English sparrow as a very misunderstood and misrepresented species. Like the starling-apologist group, though, the Humane Society is a bit selective in their facts and seems to intentionally ignore less seemly features of this bird.

We have to remember that there is no good or evil in nature. Survival for any species in any environment can require some ugly behaviors and some seemingly cruel strategies. A moral system and society based on Nature would be a very unpleasant place to live! European starlings and English sparrows are here to stay. I guess that we have to just get used to them!

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Signs of Summer 3: Ancient Ecosystems Underfoot

H. Harder, Wikimedia

H. Harder, Wikimedia

One of the Big Ideas in Biology that has grown clearer and more compelling to me over the years was very well expressed by the German biologist Ernst Haeckel back in the Nineteenth Century: “Nothing is constant but change. All existence is a perpetual flux of being and becoming.”

Organisms change, ecosystems change, climates change, genes change, proteins change: change is the common currency of an individual’s life experience and also the essence of all extended and interconnected life experiences. Last week, my daughter Marian and her friend Lee Drake were here for a few days on a short, summer break. Marian was on her way from Albuquerque to a month at a research station in Uganda, and Lee was taking a much needed respite from his extensive worldwide business traveling. They headed out one afternoon to go look for fossils and came back with a car load of shale from a road cut just north of Ford City.

We spread the rocks out on a table down in the basement and began to brush and clean the pieces. The fossils were stunning! I found my fossil books and we started putting names on some of the specimens. We also made inferences on the age and type of the shale layer that they were from based on the types of fossils that were present. Lee described the crunching feel of fossil-rich shale debris underfoot as they poked and explored the fresh road cut for specimens.

Pecopteris (D. Sillman)

Pecopteris (D. Sillman)

There were three main types of fossils: a tree fern fossil called Pecopteris, a seed fern fossil called Neuropteris, and sphenopsid (“horsetail”) called Calamites. The abundance of these three plants helped us to determine that these rocks were part of the Mahoning shale layer. This shale was laid down about three hundred million years ago during the later (“Pennsylvanian”) portion of the Carboniferous Period. This site in which these shales formed was a swampy forest located on a delta plain near the coastline of one of the world’s incredibly extensive oceans (painting above by H. Harder). Now this ecosystem and its location does seem quite a change from the present day mixed hardwood forests that dominate our landlocked Western Pennsylvania, but there were other differences that were even more overwhelming!

Neuropteris (D. Sillman)

Neuropteris (D. Sillman)

To begin with what we now call “Pennsylvania” was attached to a massive continental assemblage that included not only North America but also South America, Africa, Europe, Asia, Australia, Antarctica, and India. This was the giant continent called “Pangea,” and it contained all of the major land masses of the Earth! All of the rest of Earth was one, continuous ocean!

Further, Pangea was located far down in the southern hemisphere! “Pennsylvania” was on its northern coast and was located very near the equator! The climate here, then, was warm and tropical and had no “sun-seasons” of summer, fall, winter, or spring. Adding to the warmth of the climate was an atmosphere enriched in carbon dioxide (40% higher carbon dioxide levels than today) which trapped heat in an exaggerated greenhouse effect. Atmospheric oxygen levels were also much higher (35% of the atmosphere was molecular oxygen compared to 20% today). So each breath of air was different! Further, we were rotated about ninety degrees away from our present orientation (so our current “west” was our ancient “north”).

Calamites (D. Sillman)

Calamites (D. Sillman)

The formation of Pangea came about via the collision of the many smaller continents that each moved along on their respective tectonic plates. When these continents collided they forced masses of continental materials in between them to fold upward thus making great mountain ranges. The range near “Pennsylvania” was one of the greatest lines of mountains ever formed on Earth. The present day Himalayas are thought to be similar to this ancient, amazing up-thrust of rock and crust. These mountains were/are the Appalachians which even as they were rising began to erode to form the rocks, gravels, sands, and silts than made up the soils out of which our ancient swamp forests grew. The steady flow of these eroded materials extended the ancient shoreline out into the shallow oceans and stretched and grew the swampy forests further and further away from the mountains.

The trees of these forests were also different. There were no flowering plants on Earth and there were no deciduous trees. The trees of this ancient swampy forest were giant versions of our present day ferns and horsetails. Fifty foot tall fern trees (like Pecopteris) and one hundred foot tall horsetails (like Calamites) formed an upper canopy layer with a ground cover of other, lower growing fern and fern-like species (like Neuropteris). The warm, wet climate encouraged plant growth and the high, atmospheric carbon dioxide levels accelerated it even more. Also, the dead plants did not readily decay so the fallen branches and trunks and fronds built up in the forming soils and their eventual sedimentary rocks. This carbon accumulation was the source for most of our present day coal, and oil, and natural gas deposits (they were the fossils of our “fossil fuels!”). These ancient swampy forests are often referred to as “coal forests” or “coal swamps.”

And, just to complete the picture of change, the Earth three hundred million years ago was spinning faster on its axis than it does today. So a “day” was only 23 hours long!

We took some of the pieces of shale outside and laid them next to one of my red maples. I have collected Pecopteris before from some of the shale exposed on the down-slope to the west of my house, so adding these new fossils to the site seemed appropriate. We stood under the red maple tree and listened to the Carolina wrens singing and chattering up in the branches and watched two gray squirrels chase each other across the yard. Three hundred million years ago there were no birds or mammals, there weren’t even any dinosaurs (they wouldn’t be around for another seventy million years!). The only land dwelling vertebrates were early amphibians (sometimes their fossilized jaw bones are found in this shale) although the first reptiles with their revolutionary, self-contained eggs were possibly just evolving. There were terrestrial insects, though, some of which that had attained immense sizes because of the high atmospheric levels of oxygen. Dragonflies with two and a half foot wing spans, eight foot long millipedes, and three foot long scorpions flew and scuttled about in the warm, wet coal swamps.

The ancient forest would have been noisy with its giant insects and there might have even have been a scent of the ocean in the thick, warm air. A thunderstorm was approaching and we went inside. The rain fell on the fossils in the shale and began their slow erosion into soil.

“There is nothing permanent except change” (Heraclitus).

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Signs of Summer 2: Unexpected Oaks, Galls and Acorns

D. Sillman

D. Sillman

Nine years ago a blast of straight-line winds from a passing thunderstorm knocked down eight, fifty year old spruce trees on the west side of our house. The loss of these trees took away most of our afternoon shade out on our deck and also exposed a great deal of ongoing ecological activity about which I had not been aware.

Under several of the spruce trees were small oak seedlings. Their acorns had probably been inadvertently deposited under these long standing, heavily shading spruces by passing blue jays or crows (there are no oaks within a half a mile of my house, so these acorns had to have had very mobile carriers to get here!). These acorns had germinated in the protected micro-environment under the spruces and had been growing very slowly for possibly a decade or more waiting for some ecological opportunity. Their opportunity came in the sudden removal of the spruces whose dense shading had long ago become much more inhibiting than protective.

Over the next nine years the oaks (a mixture of white oaks, scarlet oaks, and northern red oaks) grew at an incredible rate. They are now between 15 and 25 feet tall and are rapidly spreading their branches into and over the remaining spruces undoubtedly setting to return the ecological “favor” of strangling out the spruces’ sunlight and sending them into successional oblivion.

All that drama and action right out here in my yard!

D. Sillman

D. Sillman

I was looking one of the white oak trees yesterday and noticed two remarkable things: 1. There was an odd, fluffy, spherical growth on one of the small branches of the tree (an oak gall! Specifically, a wool sower’s gall (also called an “oak seed gall”)), and 2. This small white oak (it is barely 15 feet tall and very spindly) with just nine years of open, sunlit growth had several clusters of little green acorns on its middle branches!

Oak galls:
A gall is structure in which the larvae of an insect (called a “gall former”) develop. In the United States there are 2000 described, gall forming insects. Most of these gall formers are tiny wasps or even tinier midges (a type of fly). Something really remarkable to me is the fact that seventy percent of the known gall wasps make their larvae protective galls on oak trees! There are so many things to talk about here!
Galls can form on leaves, on bark, on twigs and branches, and even on roots. The gall is a structure made by the host plant out of plant cells and tissues possibly under the stimulation of chemicals that are released by the parent gall former when it lays its eggs, or from chemicals that are found in the saliva of the larvae after they hatch out and start to feed. There is also some speculation that these “chemicals” might actually be specialized, symbiotic viruses or even RNA molecules. Whatever these agents are and from whatever source they actually arise their impact is to change the composition and activity of the host plant’s growth hormones which then causes the very specific structure of the gall to form.
The gall is not only the incubator space for the larvae, it is also a food source! Gall tissues are rich in proteins and triglycerides and provide the rich nutrition needed by the larva as they pass through their immature growth phases and eventually metamorphose into adults.

This particular “wool sower” gall is caused by a small, parasitic wasp called Callirhytis seminator. It is only found on white oaks and forms in the spring. I have searched for more information about this wasp (what are its other relationships in its ecosystem? what are its other roles?) but I have not yet been able to find any more information other than it makes these galls. There are many statements about the lack of taxonomic and ecological information about the whole group of gall formers. It seems like a wide open area for study!

The gall, then, is part of the oak tree and also an extension of the gall formers’ physiology.
Most authorities feel that galls on an oak tree have very little effect on the heath or vigor of the tree. Few management or control steps are recommended to remove or to prevent the formation of these galls. But, the question that kept coming to me as I read about these galls and observed the gall on my little white oak was, “why do oak trees have so many galls?”

An answer to this question was not easy to find. After some digging around I did come across a paper by Taper and Case published in the journal Oecologia in 1987. They found that the tannic acids which are abundant in oak leaves, bark, wood, acorns and also their galls acted to help to protect the gall former’s larvae from fungal infections and, thus, greatly increased their survival and facilitated their development into adults. Now galls do not ONLY form on oaks, but possibly those insects that utilized oaks for their galls had better success because of higher rates of reproduction. In evolution even a very slight edge in reproductive success leads to selection of a trait or characteristic. This tannin-generated survival edge may explain the incredible prevalence of present day oak galls.

White oak acorns:
I went to my silvics book to read up on white oaks. I had a feeling that they were very slow in coming into reproductive maturity and, sure enough, the first thing under reproduction was the statement that white oaks start to make acorns at about 50 years of age. A few sentences down there was a qualifying statement that some white oaks might begin flowering and reproducing (i.e. making acorns) as early as twenty years of age. I apparently had one of these precocious reproducers! Maybe I need to put it on a curfew?

I checked the other oaks in the yard but found no other acorns. I don’t know whether to collect the acorns when they ripen (white oak acorns mature in 120 days and drop off the tree 25 days later, so I would look for these acorns in late September) or let the squirrels and jays and crows have them. They planted the trees after all. Thank goodness I have a few months to think about it.

 

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Signs of Summer 1: An Old Bacterium in the Summer Swimming Hole

BASF/Flickr

BASF/Flickr

In the May 1, 2014 on-line edition of “The Scientist” there was a short article entitled “Dog’s Worst Friend.” The article wasn’t about fleas or ticks or any other obvious parasites or pathogens that afflict our best friends. Instead, the article was about a kind of bacterium that every freshman biology student hears about in a deep, historical context of the Earth many billions of years ago.

These bacteria are the “cyanobacteria” (the “blue-green algae”) a once incredibly abundant, aquatic, photosynthetic bacterium that two and half to three billion years ago was thought to have formed thick, floating, colonial masses of cells over almost all of the oceans of the world. These bacteria produced molecular oxygen as a wast product from their photosynthesis, and this oxygen changed both the Earth’s atmosphere and the direction of the evolution of life. It was these same cyanobacteria, about a billion years later that entered the cytoplasm of some of the newly evolving “eukaryotic cells” to form the symbiotic organelles of “green plant” photosynthesis, the chloroplast.

“The Scientist” article, though, didn’t talk about these freshman biology topics. The article was about present day cyanobacteria that occur, usually in small numbers, as a part of the rich, complex bacterial community of freshwater ecosystems that are found all over the Earth.
Many species of these cyanobacteria produce complex protein toxins. These chemicals were probably weapons used by the cyanobacteria in the intense, on-going chemical battle with other bacteria in their crowded, resource limited, aquatic habitats. Three billion years of competition and evolution would be expected to generate an incredibly diverse array of survival strategies, and the three to four hundred different, toxic peptides produced by cyanobacteria are not an unreasonable result of this time frame and competition matrix. Usually, cyanobacteria are a small, non-threatening part of the freshwater microflora. They can, however, under certain circumstances increase greatly in numbers and produce sufficient peptide toxins to sicken or even kill organisms like dogs, or sheep, or cattle, or even people!

 

Lamiot/Wikimedia Commons

Lamiot/Wikimedia Commons

“The Scientist” article talked about Harmful Algae Blooms (“HAB’s”) in freshwater lakes and ponds. It stated that the EPA has estimated that one out of every three freshwater lakes in the United States has the potential to have a cyanobacterial HAB, and that over the past decade of data collection 100 dogs are known to have died from cyanobacterial toxins that they encountered in some of these lakes.
The details about these lakes, the reasons for these outbreaks, and the nature of the toxic peptides, though, were not sufficiently developed in this article to really grasp the full scope of this problem. So, I poked around on the Internet and found a great article by Dr. Gregory Boyer, a professor at the SUNY College of Environmental Science and Forestry in Syracuse (that’s where Deborah and I went to graduate school!) entitled “Harmful Algae Blooms, a Newly Emerging Pathogen in Water.” Here’s the link: http://www.cws.msu.edu/documents/HarmfulAlgalBloomsWhitePaper_Boyer_Dyble.pdf
So what causes cyanobacteria in freshwater ecosystems to increase to potentially toxic levels? First and foremost the primary cause seems to be phosphate pollution. Phosphates are typically a limiting factor in aquatic ecosystems, so the addition of phosphates (from sewage or septic tanks, fertilizer runoff from agricultural fields or lawns, or from animal waste runoff) would have a large impact on the ecosystem. Cyanobacteria respond quite vigorously to added phosphates! Also, cyanobacteria need water temperatures above 20 degrees C (64 degrees F). Temperatures that warm can be generated in small shallow ponds fairly easily but will occur in larger lakes only at the end of a summer season. So, usually, large cyanobacteria blooms occur in the late summer!
There are a few other interesting features of cyanobacteria also come into play during a bloom: 1. Cyanobacteria contains gas filled, intracellular vacuoles (therefore they float!), 2. Cyanobacteria require high levels of sunlight to run their photosynthesis (therefore they NEED to be on the top of the water), 3. Cyanobacteria are not very high quality food sources for zooplankton (they tend to get left behind after feeding and grazing … maybe the peptides have something to do with this, too?), 4. Cyanobacteria clumped together into large colonies (which may be too large for most zooplankton to consume), and 5. Cyanobacteria can obtain the nitrogen they need to grow directly from the nitrogen gas of the atmosphere (they are “nitrogen fixers”).
So, the floating, clumped together masses of cyanobacteria when they get their population boost from the phosphates and the warm temperatures of the water (they are already making the nitrogen that they need!) tend to survive and accumulate in their ecosystems and crank out their hundreds of different toxic peptides! These toxins then can sicken and/or kill waterfowl, livestock, dogs, and even people! There is also a concern that chronic, low level ingestion of these toxins can lead to liver damage and even liver cancer in humans! Drinking water taken from surface water sources need to be checked for these dangerous bacteria!
Good control ideas that arise from those specific features of the cyanobacteria include stopping phosphate pollution (only use phosphate-free detergents!) and setting up fountains and bubblers in small ponds to break up any surface films and cycle the cyanobacteria to lower (and less optimal (colder and darker)) water levels.
In nearby Sewickley, Pennsylvania in 1975 there was a cyanobacterial contamination of the city’s drinking water. Sixty-two percent of the water system’s customers experienced gastrointestinal illnesses attributable to the toxins in the water. There are many historical events from all around the world in which humans or livestock or waterfowl were seriously harmed by cyanobacteria toxins.
So, when you and your dog go the local swimming hole (if such a thing still exists), if the water is scummy and smells bad, stay away from it! There are a lot of other things to do on a warm summer day!

 

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Signs of Spring 13: Ants, Cats, Acids, and Aspartame

William Cho (Flickr)

William Cho (Flickr)

The essence of science is making observations and then constructing models that explain those observations. Once your model is established you then test it (this is the “experiment” part of the scientific process) and then re-write it or throw it out, or, if it seems to stand up to your test, very tentatively accept it. Sometimes this process happens in a blur of interconnected events or mental leaps, and sometimes it happens slowly and methodically over many months or years.
I made an observation the other day as I was cleaning up our deck in anticipation of company coming over. On the deck railing, under a piece of indoor-outdoor carpet were several hundred ants. When I moved the carpet the ants began to scurry about grabbing up their larvae, and rushing into safe spots down in between the spaces of the deck timbers. I used a broom to sweep the lingering ants off of the railing and send them down into the flowerbed below (although if company wasn’t coming over I probably would have just watched them for a while). Several ants, I think, were damaged in the sweeping, but most tumbled down into the plants and, I am sure, set up their colony in a more appropriate spot. I set the broom down and noticed a few minutes later that both of my cats were rubbing and rolling on the broom like it was the finest cat-intoxicant they had ever encountered.

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Signs of Spring 12: Tree Frogs!

About three weeks ago it had finally gotten warm enough in the evening for Deborah and I to sit out on our deck. This is a great time of year to sit outside in the developing darkness: there are no swarms of summertime mosquitoes yet, and the evening is full of great sounds. The robins are singing their nightly roosting songs, and the cardinals and the wrens are singing their territory songs. Also the leaves on the trees that encircle the deck are getting large enough that they have begun to seal off and hide our sitting space. Sitting very still we feel like we have become part of action around us!

douglas mills (flickr)

douglas mills (flickr)

Another song popped up into the night time concert a couple of weeks ago. It was a chirping, whirling song from many, widely scattered voices. The song started as the daylight began to fade and kept up all through the night. Every year the same thought process crawls through my conscious brain when I hear this song: what kind of bird is that? That’s not a bird! Is that a raccoon? What IS that? Oh, yeah …. Tree frogs!

The gray tree frog (Hyla versiciolor) (pictured above) is a close relative of the spring peeper (Hyla crucifer (which is now more properly called “Pseudacris crucifer”)). We heard the choruses of the spring peepers back in March. The gray tree frogs emerge from their hibernation sites down in the leaf litter and wet, woody debris of their forest habitats later in the spring than the peepers and use their larger body size (they are 1.5 to 2 inches long compared to just an inch for the peeper) to generate a louder, deeper, more resonant song. As in the peepers the male tree frogs are the ones doing the singing. The male tree frogs, though, are primarily solitary (as compared to communally chorusing peepers) so their songs are not as organized or as synchronized as the peepers’ “compositions.” Like the peepers, the tree frogs are trying to impress and attract their females to meet them in their surrounding ponds and puddles of water in order to mate. Their singing can go on for weeks or sometimes even a month or more!

The gray tree frog is found throughout the eastern United States. It lives in trees and shrubs around ponds or seasonal wetlands. Although they are called “gray” they actually can have a range of colors from almost black to a very light green or even white. They can also change their skin color to match their surrounding substrates. These frogs are very good at camouflage (and are, subsequently, very difficult to find!). Their skin has more warts than a typical frog (but less than a typical toad!). They also have yellow patches on the inside of their back legs which are visible when they jump. The males have dark colored throats, and the females have white colored throats.

If a male successfully draws a female into his mating area, the smaller male will cling to the back of the female (an arrangement called “amplexus”) and wait for her to release her eggs into the water of the pond or puddle. He then releases his sperm and fertilizes the eggs. Small clusters of the fertilized eggs stick to the water plants and hatch into tadpoles after three to seven days. After six to eight weeks of aquatic life, the tadpoles metamorphose into froglets that hop up into the surrounding vegetation in search of very small insects. The rapid, early life development of this species probably reflects the transient nature of its mating habitat’s water sources! There is a distinct rush to get onto land as quickly as possible!

The gray tree frog has mucous secreting pads on its toes. These sticky toe pads enable it to cling tightly to tree bark and climb easily through its arboreal habitat. It is a voracious, nocturnal predator of insects and can sometimes even be found outside a lit window of house (sometimes even sticking onto the window!) feasting on the flying insects that are attracted to the light.

The evening chorus of the gray tree frogs is still going on around my house although its intensity is waning. The small creek down in my lower woods is keeping the spring pools around it full enough to support the tadpoles. We need a few good spring rains to keep the creek flowing for the next six to eight weeks, though.

It is transitioning into summer all around us! The adult titmice and house finches are feeding their demanding fledges at our feeders. The cardinals and chickadees will soon join them in a frantic rush to get brood number one weaned and fledged so that brood number two can be started. The June bugs are even buzzing at the screens on our porch! (a much nicer sound than stink bugs buzzing inside the house!). I even have a yard full of small rabbits (this year’s early brood?) who look like they are thinking about reproducing! The air is getting warmer and more and more humid and everything is green and growing!

Enjoy!

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Sign of Spring 11: A Walk With Some Birds

In spite of the looming storm clouds we headed off to the Rock Furnace Trail late Saturday afternoon for a three mile hike. We expected that the trillium that was just getting started last week would be in its full glory, and we were not disappointed! Also, so many friends have been telling us about arriving migrant bird species (including Lynn Ramage with a “birding trifecta” at her feeder one morning – indigo buntings, scarlet tanagers, and rose-breasted grosbeaks – Patrick Kopnicky with his first hummingbird of the season, and the Harrison Hills Bird Walk with Paul Hess turning up 55 species including 9 species of warblers and a great collection of vireos, flycatchers, orioles and tanagers). We were hoping to see some new birds, and we were not disappointed in that either.

Trillium grandiflorum at Rock Furnace Trail, Apollo, PA
Rock Furnace is a great place for the large-flowered trillium (Trillium grandiflorum ). Maybe it is the neutral soil pH or the stable, established deciduous tree cover, or maybe it is the steep slopes of the ravine that keep deer from too heavily cropping back the plants. Or, maybe this area has great populations of ants to disperse the trillium seeds! Possibly all of these factors come into play to make this ravine one of the finest places in the state to see this flower! There were small patches of this white trillium almost immediately, but about a mile along the trail the ravine slope on the opposite side of the stream was carpeted with blooms (photo by D. Sillman). It was breathtaking!

Male scarlet tanager at Rock Furnace Trail, Apollo, PAWe walked to the junction of Roaring Run creek with the Kiski River and then turned to go back up the Rock Furnace Trail. About a quarter of a mile along the trail I saw a flash of blue up in some of the still bare-branched white ash and red oak trees along the trail. Thinking it was a indigo bunting or black-throated blue warbler, I re-positioned myself on the trail so that I could more easily see into the thicket of branches. Whatever had been blue quickly vanished, though. Actually, he might have been there but my attention was diverted to two, bright red, male scarlet tanagers that were (quite peacefully) sharing a branch up in an ash tree (photo of one the tanagers by D. Sillman) .

These two male tanagers looked like they had just arrived from their long migration from their over-wintering sites in the foothills of the Andes in northern South America. They had spent the winter in large, mixed species flocks of flycatchers and some resident tanager species and migrated in stages first across the Gulf of Mexico and then steadily northward across the eastern United States. Very soon, though, the camaraderie of winter and migration flocking would give way to the ego-centrism of claiming a mating territory. Each male scarlet tanager needs exclusive license to 25 to 30 acres of un-fragmented woodland around its nesting site to have a chance at successful reproduction. Think of all of the insects they will have to consume to fuel the growth and development of their brood of young!

The female tanagers will arrive in a week or two. By then the males will have divided up the forest into their individual spheres of influence and will concentrate on impressing a female with their energy and vigor. The female tanager after she selects a male makes a loosely constructed, cavity-shaped nest out of twigs, rootlets, weed stems, and grasses. She then lines the nest with pine needles and fine grass. Nests are typically located in trees twenty to forty feet above ground level although some nests have been observed over a broader range of four to seventy-five feet above the ground. Eggs are typically laid from mid-May to mid-June. These eggs are a pale blue-green with brown speckles and are laid in clutches of four or five. The eggs are incubated for 13 to 14 days by the female. The young remain in the nest for 9 to 11 days after hatching and are brooded by the female but fed by both parents. There is only one brood per year for this species. Cowbirds are well known to deposit their eggs into tanager nests much to the detriment of the survival of the tanager nestlings.

Right after we saw the tanagers it started to rain. The rain was then punctuated by lightning and thunder. The lightning and thunder, then, in response to Rob Bridge’s comment “that it could be worse,” was in itself punctuated by hail. We got completely soaked in our run back to the cars.

Around the yard: my apple trees are in flower, my scarlet oaks are leafing out, and the garlic mustard is flowering (not all events are welcome!). And, on Sunday evening, “Hubert” (our ruby-throated hummingbird of the past three summers) showed up at our nectar feeder! Spring is happening faster than I can watch!  

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