"What a thousand acres of Silphiums looked like when they tickled the bellies of the buffalo is a question never again to be answered, and perhaps not even asked." -Aldo Leopold
This past August while visiting the Weldon Spring Site Interpretive Center in St. Charles, County MO, I stumbled upon one of my favorites that I have not seen since taking entomology at the University close to 20 years ago. When first encountering this insect you immediately think it must be one of the spider wasps or perhaps the great black wasp (Sphex pensylvanicus). For those who don’t immediately flee the area and instead look a little closer, you will see this is actually a very special species of fly.
Mydas tibialis, the golden-legged mydas nectaring from one of its favorite food sources, the blossom of Eryngium yuccifolium (rattlesnake master).
Mydas tibialis (golden-legged mydas) are Batesian mimics, meaning they are harmless mimics of a potentially harmful species, such as wasps. The adult form of mydas flies are purportedly short-lived. They spend the most of their lives underground where they feed on grubs in the soil.
In order to truly appreciate the size of a mydas fly, one must see them in person. If you are familiar with the size of a typical rattlesnake master inflorescence, then you might be able to appreciate this from these photos.
After doing a short bit of research, there doesn’t seem to be nearly enough known about the life history of our mydas flies. This is a shame. Not only are they fascinating animals with much waiting to be discovered but it also looks like they can be good biocontrol agents. Hopefully it won’t be another 20 years before I find one again.
Mydas tibialis, the golden giant of the Dipterans.
Photographed in April, this Agapostemon (either sericeus or splendens) bee is seen visiting blooms of Claytonia virginica (spring beauty). Agapostemon comes from two Greek words – agapetos, meaning beloved, and stemon, for stamen – these referring to their obvious fondness and attraction to flowers, particularly those in the Asteraceae. We can tell this bee is female because males of this genus have yellow and black striped abdomens.
An Agapostemon sp. female nectaring from a Claytonia virginica bloom, April 2021, St. Louis County, MO
The eastern amberwing (Perithemis tenera), is a small member of the Libellulidae family of dragonflies. Along with its coloration, it apparently rests and behaves like wasps in which they mimic. This individual was found at Sand Prairie Conservation Area in Scott County, MO.
A little late for a Halloween post, my apologies, but I wanted to share what is probably the best-preserved example of a Gibellula-infected spider I have found to date. Gibellula is a genus of endoparasitic Cordyceps fungi that primarily infect spiders. Although the nicely preserved jumping spider (Salticidae) and the fruiting branches of the fungus is what grabs the eye, it wasn’t until I finished processing the photos that a question came to mind for me.
See the white fibers that surround the spider? I see two possible options for the origin of these. First, I should explain a little of what I have read about the life history of these parasitic fungi. Similar to the Cordyceps that infect insects, Gibellula-infected spiders become “zombies” and will typically position themselves on the undersides of leaves, as the one pictured here was found. Here the fungus finally kills its host and sends out spores that are now nicely positioned to fall upon potential new spider hosts. Back to that bed of white threads. I see one function and two possible origin ideas of these. I believe the function of these is to keep the spider anchored to the leaf so that it does not fall to the ground and greatly hinder the ability of the fungi to infect new hosts. For the potential origin, these could be mycelia of the infecting fungus, or, even better, these could be silk created by the spider, induced by the fungus to anchor itself as the last act before its death.
If you have other ideas as to the potential origin or function of this bead of threads, please let me know!
One of two Buprestidae family members I was fortunate to photograph this year. This guy was found at Bush Wildlife Conservation Area in St. Charles County, MO on 01/AUG/21.
Our neighborhood Chimney Swifts have pretty much headed south and will be missed until they come again in the spring. This reminds me of a some birds that Casey and I ran into at a location we camped at in Arkansas this spring. They were using a secluded and dark hallway that lead to bathrooms we used for their overnight roosting. This was the first time I have been so close to perched Chimney Swifts so I had to take a few pics.
This southern black widow was found at Sand Prairie Conservation Area in Scott County MO. Quite unusually, she had built a web in the open within the tallest branches of a Polygonum americanum (American jointweed), where she had just dispatched a Dielis plumipes (Feather-legged Scoliid Wasp).
This southern black widow female was found wrapping up her prey, a feather-legged scoliid wasp at Sand Prairie C. A.
My shadow cast as I took photos caused her to head for cover.
I also found a male southern black widow moving about the boundaries of the female’s web.
More from Sand Prairie Conservation Area. These members of the bee fly family (Bombyliidae) were owning this patch of blooming Stylisma pickeringii (Convolvulaceae). Be sure to check out the image of a male coming in to spit game at a female that was not giving him the slightest bit of attention.
This summer I finally got to spend a little quality time wandering through Sand Prairie Conservation Area in Scott County, MO. Within and bordering the dunes one walks by large numbers of Stylisma pickeringii (Convolvulaceae) and Polygonum americanum (Polygonaceae), the later called American jointweed. If you arrive at or near sunrise there does not seem to be a lot of interest in regards to pollinators. Wait until the day heats up, say around 9 or 10 am, and then things get hopping. I saw all sorts of insects I had never seen before, mostly in the Hymenoptera. One of these was the green-eyed wasp (Tachytes sp.). Of course, when everything is warmed up, getting the photographs you want of these small and active insects becomes an epic story of frustration. But, try and try again and you might get something you’re happy with. The following pics aren’t as nice as I had hoped but I think they show this splendid little wasp as you might find them in situ.
A green-eyed wasp (Tachytes sp.) nectaring at a blossom of Polygonum americanum (American jointweed) as the gracious photographer works.
With a head that is almost all eyes, the green-eyed wasp (Tachytes sp.) is always wary and alert to potential threats.
For the past few years I have noticed a good number of native bee nest holes along exposed sections of bare soil at one of my favorite hiking and nature observation sites – August G. Beckemeier Conservation Area in St. Louis Co., MO. This past spring I finally decided to make this a project and set about a quest to make some images of these gals provisioning their nests. As usual, I wound up learning along the way.
An Agapostemon virescens pauses at the entrance of the largest of the communal nest entrances I observed. It is impossible for me to accurately count the number of females using this ~ 10 cm tall conical entrance, but I observed six individuals at one time on or hovering above the entrance.
As is commonly known, many of our native bees are solitary and nest without close contact or cooperation in regards to conspecifics. At the opposite side of this spectrum of sociality in the Hymenoptera are most species of bumble bees and the honeybee. These bees are considered truly social, or, eusocial. The characteristics necessary to be considered a eusocial species are 1) cooperative care of offspring of others within the colony, 2) overlapping generations within a colony of adults, and 3) a division of labor into reproductive and non-reproductive groups. Many of our bee species lie somewhere between these two extremes. The bee of focus here, Agapostemon virescens, lies early in the area we call being presocial, aka parasocial.
Two Agapostemon virescens females exiting a communal nest entrance having dropped off their loads into their individual cells.
Let’s clarify the differences between a presocial species such as A. virescens and the eusocial honeybee. The honeybee shows all three necessary characteristics of a eusocial species. The individual workers obviously care for brood that are not their own – they don’t even have offspring of their own, instead spending much of their lives caring for the offspring of their queen (sisters). They have multiple overlapping generations within the hive in a particular season, as well as across multiple seasons and as just mentioned, there is a division of labor into reproductive and non-reproductive castes.A. virescens on the other hand, is not nearly as cooperative. Individuals of this species share basically just a front door to their brood chambers and nothing more. After entering the communal nest, each female builds their own brood sub-chamber cells and each provisions their own by processing pollen into cakes and leaving them in their respective brood chambers. There is no brood care after the egg is deposited and the sub-chamber sealed. The offspring then emerges later in the summer.
So, what are the pre-conditions necessary for the eventual development of more complicated forms of sociality, i.e. eusociality? Or more directly, what advantages are there in adopting more of a social lifestyle if we assume the starting point was a solitary existence? Scientists consider two important pre-conditions need be met for the evolution of eusociality. First, the species offspring must be altricial, or require a great amount of parental care in order to reach maturity. Second, there need be low reproductive success rates of solitary pairs that attempt to reproduce. Here is what is believed to be the primary driver that pushed A. virescens into this presocial condition.
A sentry Agapostemon virescens stands guard at the communal nest entrance allowing only conspecifics to enter. This guarding of potential kleptoparastism is regarded as the primary benefit that led to communal nesting in this species.
This sentry Agapostemon virescens closely inspects an incoming conspecific. How it is determined who stands watch while its neighbors forage is not known.
Kleptoparasitism is where one animal takes advantage of the hard work of another by taking their prey or collected foods. In this case, we are primarily concerned with the large group of bees known as cuckoo bees. Kleptoparasitism has evolved numerous times in the Hymenoptera and cuckoo bees lay their egg on or near the host’s provisions. The parasite will hatch first and eat the host’s pollen and will often kill and eat the host’s larvae as well. With such an obviously successful reproductive strategy, it should come as no surprise that there would be a strong selective advantage of finding ways to thwart these parasites. In the case of A. virescens, evidence suggests that by communal living as described here, the rate of kleptoparasitism is much lower when compared to related species that have the completely solitary reproductive strategy.
A busy day of bringing in pollen provisions for these Agapostemon virescens sweat bees.
I guess the obvious next question is how in the world could eusociality evolve from this state? This is a fascinating story that involves terms like kin selection, altruism and haplodiploidy. It also involves a good deal of math and explanation from some of the greatest evolutionary thinkers since the time of Darwin (read anything by William D. Hamilton for example). It is also well out of the scope of this piece. But, I hope it is clear that before getting near the high rung of eusociality on this ladder, that a small first step like seen in this example would be necessary.
Although Agapostemon virescens sweat bees are communal nesters, this photo gives a clue that they are not cooperative foragers like the honeybee. Each of the three returning females is carrying different colored pollen, indicating different pollen source plants for each.
I hope I got most of this correct enough. It’s been a long time since I took Zuleyma Tang-Martinez’s Evolution of Animal Sociality class at University, which I thoroughly enjoyed. Please feel free to leave a comment to correct or clarify or ask a question.
Much of what I covered here and a lot more can be found in Malte Andersson’s The evolution of eusociality (Ann. Rev. Ecol. Syst. 1984. 15:165-89
A Thousand Acres of Silphiums 