Frost Curators' Blog

Musings and miscellanea from the Frost Entomological Museum

Field Guide to the Herb and Bramble Gall Wasps of North America

We are excited to announce that two entomologists at the Frost Entomological Museum, myself and Charles Davis, have just published a field guide covering herb and bramble gall wasps of North America! This guide is open access and free to download! It showcases much of our recent and ongoing research on these wasps, and is the most complete listing of galls occurring in association with herbaceous plants and brambles. The abstract for this publication as well as a link to its page in Penn State’s ScholarSphere repository, can be found below.

“Galls induced by cynipid wasps are one of the most impressive and unusual aspects of plant-insect interactions, but those associated with herbaceous plants and brambles are poorly studied. In this field guide, Penn State entomologists Louis Nastasi and Charles Davis present a survey of over 30 types of galls occurring on herbs and brambles in North America, many of which are documented herein for the very first time. Also discussed are tips for collecting and rearing galls, and how individuals and the public can get involved in gall research.”

Available here: https://scholarsphere.psu.edu/resources/1acfec30-7e4d-4130-98f5-46ab75972e08

Wasp Wednesday Week 10: Antistrophus Gall Wasps

Wasp Wednesday Week 10: Antistrophus Gall Wasps

This week is all about the gall wasp genus Antistrophus, my most recent research obsession. Read on to find out what makes this group especially exciting, and why their conservation is critical to endangered North American ecosystems!

Antistrophus jeanae female - lateral habitus
Antistrophus jeanae female – lateral habitus

 

This group is part of the family Cynipidae, a group of over 750 species that are known to occur worldwide. Cynipidae contains a number of subgroups called tribes that are categorized by host plant – Cynipini (oak gall wasps) is currently the most diverse based on the number of known species, but this group also received the greatest attention in research. The other 11 tribes are all equally interesting and worthy of study, especially Aulacideini, which contains many types of herb gall wasp and includes the genus Antistrophus.

Antistrophus currently consists of 10 species that all form galls on plants of the family Asteraceae, particularly Silphium, Chrysothamnus, Lygodesmia, and Microseris. The most noteworthy of these is the first one, Silphium: this genus includes a number of important plants that are specialists in North American prairies. Prairie ecosystems in North America are among the most threatened habitats – as much as 99% of their former geographic range has been cleared, primarily for use as agricultural land, meaning the conservation of the remaining habitat is a critical goal for conservation biologists.

Antistrophus silphii female - lateral habitus
Antistrophus silphii female – lateral habitus

When Antistrophus galls are found in prairies, they are often incredibly abundant, although they are often entirely unseen. Most species induce imperceptible galls within the stems of their host plants that can’t be detected from the outside – the only way to tell if the galls are even there is to cut a stem open and examine the internal tissue for signs of galling. In fact, only one known species will produce always-visible galls: Antistrophus silphii produces large, club-like galls at the tips of Silphium stems, which can grow to one or two inches across!

Antistrophus silphii galls being reared at the Frost Entomological Museum
Antistrophus silphii galls being reared at the Frost Entomological Museum

Because of their abundance and galling lifestyle, Antistrophus wasps play an especially important role in prairie systems as so-called “ecosystem engineers”, as they act as the foundation of an absolute ton of ecological interactions between many different organisms. The foremost of these would be parasitic wasps, especially those in the superfamily Chalcidoidea – these insects entirely rely on Antistrophus wasps to complete their own lifestyles, and need to lay their eggs in galls in order to reproduce. Many other animals also eat or otherwise interact with these galls, meaning that Antistrophus wasps drive a large amount of activity in prairie ecosystems. Evolutionarily, the presence of these wasps has greatly influenced the development of prairies, but we’re still uncovering how they’ve fostered the diversity and functionality of these systems. As a result, these wasps are crucial considerations within conservation programs concerning prairie systems where they occur!

We’re still learning to understand the importance of these wasps in their native ecosystems, but the emerging picture appears to be that these insects will remain an important study topic for decades to come! Silphium, the same host plant that makes Antistrophus an important prairie insect, is currently being domesticated for use in biofuels, which brings even more relevance to these gall wasps. We’re also uncovering possible undescribed species within the genus! Overall, examining this crucial group of gall wasps will undoubtedly yield many valuable insights into prairie conservation, biotechnology, and systematics!

View This Taxon On: BugGuide | iNaturalist

The photos of Antistrophus silphii and Antistrophus jeanae have been graciously provided by Frost Museum research associate and Hines Lab postdoctoral scholar Antoine Guiguet – you can see more of his work, including more photos of gall wasps, on his website!

Wasp Wednesday 9: Scolia dubia dubia Say, 1837

Wasp Wednesday Week 9: Scolia dubia dubia Say, 1837

This week marks the return of Wasp Wednesday, meaning we get to discuss another fun constituent of the order Hymenoptera! Up this week is Scolia dubia dubia, a common and conspicuous wasp that you can easily find in your garden or on a hike.

Figure 1: Scolia dubia dubia dorsal view
Figure 1: Scolia dubia dubia dorsal view

Taxonomy: This species is a member of the family Scoliidae, a group of over 550 species that are known to occur worldwide. These wasps are sometimes referred to as crinkle-winged wasps due to the appearance of their wings. There are approximately 20 North American species in this family, and recent taxonomic work has placed them into seven genera. The family was formerly placed in the superfamily Vespoidea, although recent molecular research suggests Scoliidae belongs in its own superfamily Scolioidea. Scolia dubia dubia is one subspecies of Scolia dubia, and is often referred to as the two-spotted scoliid wasp. The other subspecies, Scolia dubia haematodes, is found in western North America, especially in the southwest. This other subspecies has one of the most hardcore common names I’ve ever seen – the BLOOD-TAILED SCOLIID WASP!

Identification: Scoliid wasps are often conspicuous and easily noticed. Most species are between half an inch and an inch in length, although some tropical species can grow to two inches, with wingspans up to nearly 5 inches! The North American species are either yellow or red with black markings and dark wings. The family can be easily separated from most other wasps by examining the wings, which have many wrinkle-like ridges at the tips of their wings. Scolia dubia dubia is easily separated from other scoliids (and most other wasps) by the two yellow spots on the dorsal metasoma. If you look closely, you might notice that this wasp bears a close resemblance to a famous cartoon mouse – interestingly enough, they’ve been observed on iNaturalist at Universal Studios in Orlando, but not yet at Disney World!

Figure 2: Scolia dubia dubia lateral view
Figure 2: Scolia dubia dubia lateral view

Natural History: Scolia dubia dubia can be found throughout the eastern United States, although members of the family are widespread throughout all of North America as well as globally. The two-spotted scoliid wasp will collect nectar from flowers in the late summer and early fall. Scoliid wasps all hunt the grubs of scarab beetles (Coleoptera: Scarabaeidae), on which the females lay their eggs. Once larvae develop, they will enter the body of the host, feed, and overwinter until they mature. Scolia dubia dubia is known to hunt for grubs of the green June beetle, Cotinis nitida, and also may hunt the invasive Japanese beetle, Popilia japonica, which makes this species a key ally in the fight against invasive species in North America!

View This Taxon On: BugGuide | iNaturalist

Wasp Wednesday Week 8: Atta cephalotes (Linnaeus, 1758)

Wasp Wednesday Week 8: Atta cephalotes (Linnaeus, 1758)

Figure 1: Atta cephalodes anterior view
Figure 1: Atta cephalotes anterior view

This week’s wasp is… a bit different than the previous weeks! My feature for this week is the leaf-cutter ant species Atta cephalotes! This species was first described by Linnaeus, the infamous taxonomist and founder of binomial nomenclature. This particular specimen was once part of a lab colony maintained at Drexel University which originated from Panama.

Wait – you might say – this is an ant! Why is it being featured for Wasp Wednesday? As it turns out, ants (which make up the family Formicidae) are wasps! Ants are an interesting case within the order Hymenoptera; like bees, ants are essentially never considered to be wasps in a vernacular sense. From an evolutionary perspective, ants are descended from an assemblage of wasps formerly known as the superfamily “Vespoidea”, which places them closely related to Vespidae (yellow jackets, paper wasps, and hornets) and many other groups of conspicuous stinging wasps. The exact reason for this lack of broader inclusion within “wasps” is somewhat uncertain, but it is likely because of their general differences in both morphologically and societal perception. Ants, like bees, just seem different, but they are indeed wasps nevertheless! Now, without further ado, let’s move on to the species profile!

Taxonomy: This species is a member of the family Formicidae, which contains the ants. A handful of other hymenopteran groups are sometimes referred to as ants, particularly the “velvet ants” of the family Mutillidae, but only members of Formicidae can be considered true ants. The ants are one of the most diverse groups within the order Hymenoptera, and currently includes over 12,000 described species worldwide. This diverse group has been very well studied from a taxonomic perspective, and is currently grouped into sixteen extant subfamilies. The genus Atta is placed in the subfamily Myrmicine and the tribe Attini, and currently contains seventeen described species.

Figure 2: Atta cephalotes dorsal view
Figure 2: Atta cephalotes dorsal view

Identification: For the most part, ants are easy to identify. The most commonly-encountered ants are female workers, which are mostly easily distinguished from other hymenopterans by their lack of wings. However, in the case of male ants (which are winged) or other wingless wasps, more-discrete characters are necessary to determine whether or not something is an ant. Luckily, these characters are more-or-less universal across all ants. The first of these characters is the antennae, which are elbowed. The antennae are formed from a long first segment and a series of smaller segments bent off the first at a distinct angle. The second useful character is the segmentation of the metasoma – the basal segments of the metasoma of an ant are node-like, and the remaining segments look like typical wasp metasomal segments. There are a handful of other characters that might be useful, but these listed here should be sufficient for separating most ants from other insects.

This species is separable from other ants by the presence of a pair of large spines on the pronotum, two pairs of spines on the promesonotum, and a distinct lack of tubercles on the gaster.

Figure 3: Atta cephalotes lateral view
Figure 3: Atta cephalotes lateral view

Natural History: Ants are eusocial organisms, which means they operate within a “society” – that is, each individual ant is part of a regimented hierarchy within its respective colony. Most species have a single female reproductive called the queen, female workers, and male reproductives. Members of the genus Atta are known as leafcutter ants, which are known for their habit of cutting off chunks of leaves and carrying them back to their nests.

Many species of leafcutter ants form “highways” on the forest floor; these are paths that the colony uses to transport leaf material. The ants are quite territorial of their highways – anything that invades their space may be subject to attack. Leafcutter ants cut leaf pieces in order to grow fungus on them, which then becomes the food source of the colony. This fungus is cultivated within the nest below the ground.

Interestingly, leafcutter ants appear to have evolved the tendency to constantly change food plants. This practice is likely greatly beneficial, as it prevents the ants from completely stripping the leaves from any given plant, which would almost certainly result in the plant’s death.

The species Atta cephalotes is found from Mexico all the way to Ecuador and Brazil, making it the most widespread species of leafcutter ant.

View This Species On:

iNaturalist: https://www.inaturalist.org/taxa/153974-Atta-cephalotes

AntKey: http://antkey.org/en/taxa/atta-cephalotes

Encyclopedia of Life: https://eol.org/pages/53197

References:

  • Aguiar, A. P., Deans, A. R., Engel, M. S., Forshage, M., Huber, J. T., Jennings, J. T., … & Miko, I. (2013). Order Hymenoptera. In: Zhang, Z.-Q.(Ed.) Animal Biodiversity: An Outline of Higher-level Classification and Survey of Taxonomic Richness (Addenda 2013). Zootaxa, 3703(1), 51-62.
  • Goulet, H., Huber, J. T. (1993). Hymenoptera of the world: An identification guide to families. Ottawa: Research Branch Agriculture Canada.

Wasp Wednesday Week 7: Chrysis nitidula Fabricius, 1775

Wasp Wednesday Week 7: Chrysis nitidula Fabricius, 1775

Chrysis nitidula lateral view
Figure 1: Chrysis nitidula lateral view

This week’s wasp is the cuckoo wasp species Chrysis nitidula! This species was first described by Johan Christian Fabricius in the year 1775. This specimen was collected by Frost Museum namesake Stuart Frost in 1958, and was identified as this species (as synonym Chrysis coerulans) by the hymenopterist Karl Krombein. These wasps are both beautiful and bizarre – read on to learn more about their life histories and what makes them some of the most-beloved wasps!

 

Taxonomy: This species is a member of the family Chrysididae, which contains the cuckoo wasps. Members of this family are sometimes referred to as jewel wasps, which sometimes causes confusion with species of the family Ampulicidae. The family Chrysididae contains over 3,000 living species and can be found worldwide. More than 200 species in around 30 genera are known from North America. The genus Chrysis to which this week’s species belongs is considered by many to be quite messy and improperly-characterized, as the characters used to associate its members do not properly reflect their evolution.

 

Identification: The cuckoo wasps are often incredibly easy to distinguish from other wasp groups.

Chrysis nitidula anterior view
Figure 2: Chrysis nitidula anterior view

Members of this family are typically brilliant, gem-like colors and are almost always metallic. Many species are a brilliant emerald green and turquoise, while

others are bright red, deep blue (like this specimen), or even purple or pink! Because of their brilliant colors, they’re often referred to as emerald, ruby, or even sapphire wasps! Typical members of the family are heavily covered in conspicuous pits over much of the body. More precisely, chrysidids have thirteen antennal segments, five or fewer exposed metasomal terga, and fairly characteristic wing venation.

 

Chrysis nitidula dorsal view
Figure 3: Chrysis nitidula dorsal view

Natural History: The common name “cuckoo wasp” may remind you of the cuckoo bird (Aves: Cuculidae). In fact, the term “cuckoo” in this case is accurate for both groups. The cuckoo bird lays its eggs in the nests of other birds, and when the eggs hatch, the nest’s true owner feeds and cares for the cuckoo bird’s offspring. The cuckoo wasps exhibit this same behavior – particularly in the nominate subfamily Chrysidinae – but they take it one step further. Cuckoo wasps lay their eggs in the nests of other wasps, but instead of simply being cared for by the host, they instead eat the other eggs or larvae present in the nest and eat food provisioned for them. This unusual lifestyle is called kleptoparasitism, wherein an organism steals resources from another instead of a more direct form of parasitism.

Chrysis nitidula dorsal view
Figure 4: Chrysis nitidula dorsal view

 

View This Species On:

BugGuide: https://bugguide.net/node/view/205363

iNaturalist: https://www.inaturalist.org/taxa/937971-Chrysis-nitidula/

 

References:

  • Aguiar, A. P., Deans, A. R., Engel, M. S., Forshage, M., Huber, J. T., Jennings, J. T., … & Miko, I. (2013). Order Hymenoptera. In: Zhang, Z.-Q.(Ed.) Animal Biodiversity: An Outline of Higher-level Classification and Survey of Taxonomic Richness (Addenda 2013). Zootaxa, 3703(1), 51-62.
  • Goulet, H., Huber, J. T. (1993). Hymenoptera of the world: An identification guide to families. Ottawa: Research Branch Agriculture Canada.

Department of Entomology, in the College of Agricultural Sciences, at Penn State

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