Happy 209th Birthday, Darwin!

Charles Darwin was born on February 12th, 1809. Last year, I had the pleasure of taking a class taught by Benoît Dayrat focused solely on reading and discussion Darwin’s “On the Origin of Species”, which I would like to discuss today in honor of Charles Darwin on his birthday.

Darwin is most famous for his theory of descent with modification, but he also had early ideas about kin selection, where natural selection favors behavior by individuals that may decrease their chance of survival but increase that of their kin (who share a proportion of their genes). Though he was one of the greatest scientific thinkers of the 19th century, he was limited by the scientific knowledge available to him in his day; he wasn’t aware of continental drift, and thought that all species spread by migration only.

A statue of a young Charles Darwin, which stands at Cold Spring Harbor Laboratory in NY. Photo by Nathan Siemers (CC BY-SA 2.0). Click for source.

Darwin anticipated that his book would not be well received. He thought very carefully about how to overcome this, developing his ideas and collecting data for over 23 years. In his writing, he presents both well-known facts and data from his own experiments to prove his points, but he goes much further than this.

He crafts his writing to build a convincing argument that relies on logic and reason as well as fact. He introduces his ideas very slowly, and repeats them over and over so that the audience can become accustomed to them and understand them fully. In some cases, he asks questions and then accompanies the audience along a logical trail of thought until they come to the same conclusions themselves.

Darwin anticipates the weaknesses in his theory. He presents these weaknesses as “grave difficulties” to his audience, but this is often an exaggeration; after presenting each “grave difficulty”, he then explores the issue in detail, taking it apart piece by piece and showing how the “difficulty” actually fits into his theory of descent with modification. Oftentimes, he is even able to show that the issue at hand can only be explained by descent with modification. By the end, they are hardly “grave difficulties” at all, but arguments proving his point.

An illustration of a bat from Charles Darwin’s “Zoology of the Voyage of H.M.S. Beagle, 1839–43, vol. 1, Mammalia”. Image from APS Museum (CC BY-NC 2.0). Click for source.

Darwin takes every opportunity to attack independent creation, spending a large portion of one chapter dismantling the idea that an eye is a perfect structure that could only have been created by divine means. He compares the eye to a microscope— though it may seem to work perfectly, it was not created in a single day. Instead, it was the result of many modifications to a structure over the course of several years. In another section, Darwin points out that bats are the only native mammals found on marine islands, and asks why a divine being would only create bats there and no other mammals. He says that this is clearly not the product of divine influence, but the result of migration; bats can migrate to places other mammals can’t.

Darwin thought that we should not marvel at the perfection of nature because there is no perfection in nature (he asks that if nature was perfect, then why would a bee die after stinging?). The reason there is no perfection in nature is because all organisms are a product of their history, not perfect creation.

Darwin believed that a species was just a variety that became more distinct over time. If Darwin were alive today, he would say that it is impossible to discover species because they are undiscoverable; the term “species” is arbitrary. We should not focus on what the qualities or essence of a “species” is; instead, we should wonder about its history.

An illustration from the The Boy’s Own Paper, 1892, showing several varieties of fancy pigeons. Charles Darwin bred pigeons himself, and discusses them several time in his “On the Origin of Species”. Image by seriykotik1970 (CC BY 2.0). Click for source.

The class I took on Darwin’s “On the Origin of Species” was an enlightening experience for all involved. Other students in the class were impressed by the sheer amount of experiments Darwin did and data he amassed over 23 years. Many of his experiments involved pigeons, which we joked were Darwin’s favorite, though there was one memorable experiment in which he tested if snails could travel to other ponds by clinging to the legs of waterfowl. Darwin tested this by suspending a disembodied duck leg in a fish tank full of snails.

Personally, I was impressed by his rhetoric and the eloquence of his writing. Darwin’s mastery of the English language is extraordinary, and his skill as a science communicator is something that needs to be acknowledged more. He put an incredible amount of thought into every word he wrote. A perfect example of this is in the ending: the last word of the book is “evolved”. It is the first time that this word is mentioned in the entire book, and it is the word he chose to end it on.

Special thanks to Benoît Dayrat for teaching me about Charles Darwin!

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Learning about life from dead insects: What morphology can teach us about a new species of wasp from Costa Rica

How much can you tell about a wasp’s life when all you have are dead specimens that are over 30 years old and smaller than a grain of rice?

If you have a morphologist and a good microscope, you can actually tell a lot.

When we took a look at four tiny wasps collected in Costa Rica in 1985, we knew immediately that we were dealing with a new species. It was clear that the species belonged to the genus Dendrocerus based on the dark patch on its wing, called a pterostigma, and the numerous long branches of the male antennae.

However, we didn’t know of any Dendrocerus, or any wasp in the superfamily Ceraphronoidea, that had a row of mesoscutellar spines, shown with an arrow in the picture below.

Dendrocerus scutellaris male, with an arrow pointing to the mesoscutellar spines. The male also has elaborate branched antennae that could be used for finding mates. Photo by Carolyn Trietsch (CC BY 2.0). Click for source.

What could these mesoscutellar spines be used for?

Like many wasps, ceraphronoids are parasitoids, meaning that their larvae feed on a live host insect. Some are endoparasitoids, which lay their eggs inside a live insect so that the larvae can eat it from the inside out. After they’re done feeding, endoparasitoid larvae may stay inside their hosts body to complete their development. Once they are mature, the adult wasps will then push or chew their way out.

A. Dendrocerus scutellaris female, with a black arrow pointing to the mesoscutellar spines. The female does not have branched antennae like the male. B. Closeup of the mesoscutellar spines. Photo by Carolyn Trietsch (CC BY 2.0). Click for source.

Dendrocerus scutellaris is the only known ceraphronoid with a series of mesoscutellar spines, but this is not the only feature that sets it apart: whereas other ceraphronoids have pointed mandibles, D. scutellaris has blunt, flattened mandibles. With its blunted mandibles, D. scutellaris cannot chew its way out of a host.

This may be why the wasps have these spines; while emerging from their host, the wasps may rub the spines against the host’s body to help break or saw their way out. Similar structures have been found in other insects, including Hymenoptera and Lepidoptera.

For more about these wasps, check out our new publication:

Trietsch C, Mikó I, Notton D, Deans A (2018) Unique extrication structure in a new megaspilid, Dendrocerus scutellaris Trietsch & Mikó (Hymenoptera: Megaspilidae). Biodiversity Data Journal 6: e22676. https://doi.org/10.3897/BDJ.6.e22676

This material is based upon work supported by the U. S. National Science Foundation, under Grant Numbers DBI-1356381 and DEB-1353252. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

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Introductory Entomology Instructional Kit

In an old cabinet near the collection room, in a lab that used to be where most entomology classes were taught, reside several sets of long-forgotten 35 mm slides and cassettes.

4 upright boxes, each containing a 35mm slide carousel

Slides from the Introductory Entomology Instructional Kit, produced by the Entomological Society of America and Brigham Young University. Photo (CC BY 2.0) by Andy Deans. Click for source

I mostly ignored them since coming to Penn State, as they weren’t part of the Frost or my lab’s legacy. However, it’s clear now that they’ve been abandoned and are ripe for exploration and repurposing. I was intrigued by the names on the boxes—Carpenter, Wilson, Gilbert, Locke, Metcalf …

old skool cassette tape

Cassette tape of a Robert Metcalf lecture on insect control, part of the Entomological Society of America and BYU’s Introductory Entomology Instructional Kit. Photo (CC BY 2.0) by Andy Deans. Click for source

These are GIANTS of entomology! With a bit of digging, I figured out that we had in our possession almost two complete sets of educational materials, developed by the Entomological Society of America and Brigham Young University. The Introductory Entomology Instructional Kit was published in 1973 and cost $300 (about $1,700 in today’s money). I am dying to listen to these cassettes while working my way through the slideshows. They’re clearly outdated, but to hear the voices of these famous entomologists and to get a sense of state of entomology around the time I was born … Well, it would be amazing.

We flirted with the idea of transferring these materials to digital formats—scan the slides, transfer cassette audio to mp3, and maybe put them on YouTube if we could get permission—but that would be a lot of work, and I fear for the state of these cassettes. I haven’t tested one yet (I don’t even have a tape player anymore!), but my understanding is that magnetic tape is not archival. The life span can be as short as 10–20 years, even under ideal environmental conditions. I suspect these cassettes were played extensively in the years following 1973, and the cabinet they’ve been stored in has weathered many unfortunate events (e.g., extreme humidity from repeated flooding). If I try to play one will it fall apart?

We also thought about incorporating the slides into our exhibits somehow, probably as a back-lit, stand alone window treatment:

35mm slides against a window. the slides show insects and text about insect classification

Slides from the Introductory Entomology Instructional Kit. Could we use them in an exhibit? Photo (CC BY 2.0) by Andy Deans. Click for source

35 mm slide, held between thumb and forefinger, of E. O. Wilson at a lab bench

Photo of E. O. Wilson, who narrates the “Social Insects” portion of the Introductory Entomology Instructional Kit. Photo (CC BY 2.0) by Andy Deans. Click for source

Of course we’d want to do this in a way that protects these slides from degradation, and we’re still researching this. I wonder if ESA and BYU have the original recordings and photos in their archives. Do any of you readers have these kits?

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Illustrating Metamorphosis with Maria Sibylla Merian

This post is the fifth in a short blog series featuring important figures in the history of natural history.

Maria Sibylla Merian is considered one of the most important naturalists of the 17th  century. Though she was well known during her lifetime due to her family’s successful publishing company, one of the largest at the time, her continuing fame and influence is due to her meticulous illustrations and insights into insect development.

Her stepfather, a still-life painter, recognized her artistic potential at a young age and began to train her alongside his own students. She learned how to draw, paint and make engravings on copper under his instruction, skills that few women at the time possessed. She published plates in books about flowers, but her focus soon turned away from flowers and towards the insects that dwelt on them.

Merian was fascinated with insects from a young age, and enjoyed collecting live caterpillars to rear into butterflies. As her artistic skills progressed and her reputation grew, the wealthy and elite would invite her to view their private gardens and illustrate the plants they maintained. As she did this, Merian took the opportunity to observe and illustrate the different types of insects associated with each plant.

A male (bottom left) and female (top left) Papilio androgeus butterfly, with caterpillar and pupal case. Illustration by Maria Sibylla Merian (1647-1717), illuminated copper engraving by P. Sluyter from Metamorphosis insectorum Surinamensium, Plate XXXI (c. 1705). Image from Swallowtail Garden Seeds (CC BY 2.0). Click for source.

Illustration is a meticulous process, requiring a great deal of time and effort. Trying to translate a complex three-dimensional object into a two-dimensional representation requires a different kind of thinking, but taking such an approach can cause someone to see qualities they did not notice before and gain a deeper understand of what they are looking at.

This is why drawing can be a helpful exercise for students studying anatomy and natural history. This is also what made Merian such an effective naturalist: her background as an illustrator, combined with her passion and dedication to the natural world, led her to realize that insects are not the product of spontaneous generation. Instead, Merian was among the first to show that insects have different life stages and undergo metamorphosis.

Merian created beautiful illustrations of insects, showing their larvae, pupae and adult forms as well as their hosts and habitat. Her illustrations are so detailed and accurate that many of the insects she drew can be identified down to genus and species. She observed how some caterpillars with different coloration and different host plants still had the same adult forms, constituting some of the first observations on generalist and specialist species in Lepidoptera. She distinguished between nocturnal and diurnal species, and even observed parasitoids, proposing that flies laid eggs on caterpillars and developed inside them instead of just spontaneously generating. She published her observations and illustrations in Der Raupen wunderbare Verwandlung und sonderbare Blumennahrung, which can be translated as The Caterpillars’ Marvelous Transformation and Strange Floral Food.

When she was 52, she financed her own trip to Suriname in South America, something that was almost unheard of for a woman of her age at the time. She desired to travel to South America so that she could observe insects and other animals in their natural habitats. She was forced to return to Europe after she contracted malaria, but in the two years she stayed in South America she was able to illustrated 60 species of plants and 90 species of animals. Some of her illustrations are the only known records of those species—it is likely that those species are now extinct. The product of her travels was the Metamorphosis insectorum Surinamensium, which is regarded as her most famous work.

Today, Merian is remembered for her beautiful illustrations of insect life stages and her notes on metamorphosis. Though Merian never received formal training as a scholar or scientist, her training as an illustrator allowed her to follow in Aristotle’s footsteps and make several insightful discoveries about the natural world.


Special thanks to Shelley Whitehead for her help with this post!

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Inspirational Reading

In what ended up being an incredibly chaotic semester for me-between taking 4 classes and TAing one, running another marathon, going to ESA in Denver, and taking on the role of the Penn State Entomological Graduate Student Association Outreach Coordinator while trying to keep up with lab work, the last half of 2017 was absolutely chaotic. Therefore, some much needed restorative and inspiring reading material was necessary!

Illustration of some common dragonflies in a 1918 field book.

A page of beautiful odonate inspiration. Photo by Biodiversity Heritage Library (CC-BY-2.0), from a 1918 Field Book of Insects. Click for source.

While most of us read many articles and snippets of data a day for our own research needs, sometimes you just need to read something else. I am trying to make it a point to read something from this stack each day. Here is the start of a stack that I have been working my way through since the end of 2017.

Lab Girl by Hope Jahren is a book spanning day-to-day lab life to the way that all of the days and experiences add up to a truly meaningful career. Jahren is an incredibly skilled writer, as well as a geoscientist. Her summaries of the years of graduate school and research projects, as well as deep looks at her personal life provide a breath of fresh air for long days of research. I finished this book feeling appreciative that I am able to pursue science in a world waiting for discovery.

A Biology of Dragonflies by Philip S. Corbet has been a great reminder of all of the wonderful observations that dragonfly specialists have made before me, and it has opened my mind up to many new ideas to pursue. This is a shorter book than his other famous tome, Dragonflies: Behavior and Ecology of Odonata, but it is a great place to begin an examination of the natural history of dragonflies.

Bluets by Maggie Nelson is a book of poetry that I bought while I was in London last summer, from the delightful John Sandoe Bookstore. I confess that I bought it primarily because bluets are a common name for some damselflies in the Coenagrionidae family. So far, so beautiful.

Hopefully I’ll get through this stack of books soon and move on to my next shelf!

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