Possible ID: Elasmosoma michaeli (Parasitoid Wasp of Western Thatching Ant, Formica obscuripes)

I happened to re-encounter some photos I took 5 years ago while visiting a nest mound of Formica obscuripes (Western Thatching Ants) while I was trying to assemble the bee and wasp pictures I've taken over the years, when I was reminded of these tiny parasitoid wasps I had seen.

While I did not recall seeing these things around Thatching Ant hill before, initially I was only seeing one to two isolated wasps, and just spotting them was rather hard due to their very small size and the varying colors of the mound and the surroundings, not to mention the somewhat unpredictable flight of the wasps. Although no biologist, let alone entomologist, my interest in nature had already make me aware of a few forms of parasitism that existed in nature, and i was pretty sure one was going on here.

At first it seemed at those that ants did not even notice or pay attention to the dangerous pests, although I would sometimes notice once contact was made between the wasp and an ant. The contact was not surprisingly rather brief, as I'm guessing it might have to be in order for an egg to be placed on or in the body of another species, particularly one such as an ant that tends to appear rather quite when looked at by humans.

Over time this one summer (2012) I noticed the number of wasps increasing, and was finally able to get some blurry pictures, and finally, eventually, I would get a marginal picture of one landed for just a second. By this time I was noticing ants carrying bodies of their peers out of and away from the mound. I was not completely clear as to whether they were alive or completely dead when removed, but I would guess initially they were likely dead.

Over some time as the number of wasps increased, I noticed the ant behavior had changed and many of the ants were now aware of their presence, often turning to face them, sometimes appearing to snag or grab them, or if nothing else being able to fend off their approach, that almost always came from behind, however.

Quickly I found that when there were a number of wasps present, the Western Thatching Ants active on the mound had decreased dramatically... sometimes to the point only one or two might even be out. I would sometimes observe ant heads facing out one of the entrances as if to see if it might be safe to come outside... and guessing they felt or may have actually been safe with only their heads exposed. Any ant that seemed to be active for some reason, or at least most of the few that were, seemed as if they were crossing an aerial mine-field, perhaps having learned to detect either the sound of their wings, or perhaps the air disturbance being caused, or some other factor, but clearly they seemed paranoid and were quite aware of when wasps were getting close to them.

This had been a reasonably decent but perhaps average sized mound, and I'd observed it for a period of perhaps 3 or more years by that point. Before the end of summer it seemed rather deserted. A bit before that point I had noticed that across the road from it, a new Formica obscuripes nest had appeared, although there was not much of a mound in place, but they had developed entry holes in somewhat more sandy material that was under some rocks (4-8" in longer dimension). When I first saw it and visited it a few times there was no evidence of any wasps present, but one day I did notice one that thought "Oh no, not again". As soon as the wasps showed up the ants were quite aware, and would sometimes run from hole to hole, or to small covered trails in brambles on the fringe of their home base. It was not long before I saw all activity at this time disappear.

At the time I was living in Renton, Washington. In January 2015 I moved to SE corner of Bellevue WA, and started new walking / picture taking routes here. Although I have not spend excessive time at any of perhaps dozen ant mounts I've seen in the area, I have wanted more than enough to see that none of the nests are suffering from any excessive outbreaks of these parasitoid wasps.

So today I began doing a bit more research since I found none of my filenames containing the images contained the species name (my way of identifying images of same. From the limited pictures I've seen of this species and others, and the limited pictures I have myself, I would propose "Elasmosoma michaeli" as a candidate. I did notice this particular species is not listed in the database at this point.


AnimalGuy




I did happen to consult these two papers, but won't pretend to suggest that they support my species guess. Although it would be nice to add something to the database, I'm guessing the picture(s) are not adequate to speciate this individual in any case, but even genus confirmation would be nice. (I wish scientific research was more readily available)


A new species of Elasmosoma Ruthe (Hymenoptera: Braconidae: Neoneurinae) from the Northwestern United States associated with the western thatching ants, Formica obscuripes Forel and Formica obscuriventris clivia Creighton (Hymenoptera: Formicidae)
(c) 2007, Scott R Shaw


Diversity of Species and Behavior of Hymenopteran Parasitoids of Ants: A Review
(c) 2012, Jean-Paul Lachaud and Gabriela Pérez-Lachaud

SOURCE PICTURE FILES:
(1)--IMG_5045x...Elasmosoma_michaeli...
(2)--IMG_7875x...Elasmosoma_michaeli...
(3)--IMG_5049x...Formica_obscuripes...FendingOff...Elasmosoma_michaeli...