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.
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.
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.
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.
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.
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.
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
The evolution of Eusociality
I finally lucked out and found a late instar Battus philenor. This guy was walking along a trail, presumably looking for a good spot to pupate. I persuaded it to walk on a stick for a brief period to pose for a couple of portraits and then left it where I found it.
Back in mid-June I discovered a number of Synchlora aerata (camouflaged looper, wavy-lined emerald moth) that were using our coreopsis as host. Not only are these spectacular adult moths in the family Geometridae, but they are obviously special while in the larval phase as well. These caterpillars are known for attaching bits and pieces of the plant tissues they feed on (often flower petals) to their backs as means of camouflaging against their predators.
The Languria bicolor (Erotylidae) is placed in the tribe Languriini (lizard beetles). Larvae of lizard beetles develop within the stems of plants and adults feed on the tissues and pollen of the same or nearby plants. This individual was found in July 2021 at the Beaumont Scout Reservation, St. Louis County, Missouri.
The nine-banded armadillo invasion of Missouri is over. Armadillos have now been found near the Missouri-Iowa border and in the St. Louis metro area they are now almost as common roadkill as are racoons. I find these animals fascinating and Sarah and I once kept one as a pet for a brief time. Casey and I found several armadillos digging up plant bulbs in the fields of Peck Ranch while looking for elk last winter.
There are all sorts of interesting bits of information that can be shared about these guys. Here are a couple of my favorites. 1) Twenty five years ago you would not find armadillos anywhere in the state. 2) The armadillo is the only other known animal, besides humans, to carry the disease leprosy. These two factoids are related because they likely have the same underlying cause behind them – the lower body temperature of armadillos. Armadillos have a lower working body temperature than most mammals, maintaining it at about 89 °F. The increasingly warmer winters over the past few decades has allowed the armadillo to get through the previously limiting winters, allowing their northward expansion. Their lower body temperature also allows them to be carriers of the bacteria (Mycobacterium leprae) known to cause leprosy. This bacteria thrives in tissues of lower temperatures, such as the tips of our noses and fingers and within the armadillo.
Here we have a few shots of a small carpenter bee that was very cooperative this past April at Beckemeier Conservation Area as it nectared from a spring beauty blossom. This is one of the bees that nests and overwinters in old broken pithy stems that it excavates. So here is who you might be helping by leaving your dead stems sit through the winter.