Velvet Ant
Sandy spotted this crawling on the house siding around our front door on August 3, 2014. While this specimen looks like an ant, she isn’t. She is a species of “Velvet Ant”, which are actually wingless, solitary wasps.
I posted photos of a similar specimen back in 2012, which I had decided was most likely Pseudomethoca frigida. But, this new one looks a bit different. She has a markedly longer, more tapered abdomen and looks less hairy than the previous one, and is probably a different species. Maybe Pseudomethoca simillima.
Sandy tried to persuade me to get it to sting me so I could report on the pain level, but I declined. Partly because I am not really all that keen on getting stung, and partly because it didn’t seem all that easily provoked, and I probably would have had to squash her to get a sting. From the size, though (she was only about 6-8 mm long), I expect that it would have been a relatively minor sting. The reputation of the bigger species of velvet ants for painful stings is more based on them being big (sometimes over an inch long), and therefore able to provide a substantial slug of venom. The actual potency of their venom probably is no greater than that of other wasps.
Velvet ants are parasitoids of a variety of ground-nesting bees, wasps, and maybe ants. They get into nests of either solitary bees/wasps, or small colonies, and lay their eggs on the grubs that they find in there. I did some searching to see what is known about the hosts that the relatives of this particular velvet ant like, and found a pretty comprehensive review article on the topic from 2000, by Brothers, Tschuch, and Burger [1]. The ones that they mention in the Pseudomethoca genus proceed as follows:
1. The adult female velvet ant patrols around the nesting areas of halcitid bees (“sweat bees”), which are built by small colonies of bees. The bees usually guard their nest entrances, and the velvet ants keep trying to get in, while usually being driven off. The velvet ants are pretty ruggedly constructed, and the bees rarely do any harm to them. They keep this up until the bees let their guard down and the velvet ant manages to slip inside.
2. After getting into the nest, the velvet ant goes as deep inside as possible to reduce the chances of being noticed by a guard bee. She will spend a long time rummaging around in the nest, unplugging cells looking for the ones where the bee larva has eaten all of its food stores and is either just about ready to pupate, or already pupating. She may sting it to paralyze it and make sure that it won’t mature before her larva can eat it, then she’ll lay an egg, close the cell back up, and move on.
3. The egg hatches after 4 days, and the new velvet ant larva commences eating, and evidently grows at an outrageous rate. If this isn’t a misprint in the paper, it is done eating and starts spinning its cocoon after only 4 days, and is pupating by a mere 8 days after hatching. I guess bee larvae are very easy to digest.
4. If they aren’t overwintering[2], the males come out of the cocoons after about 12 days, and the females after about 14 days. The males have wings and can disperse[3], but they evidently tend to hang around the nest of their hosts so that they can mate with the females when they come out. At this rate, it sounds like they are fully capable of having several generations per year, with a new generation every 20 days or so.
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[1] D.J. Brothers, G. Tschuch, F. Burger (2000), “Associations of mutillid wasps (Hymenoptera, Mutillidae) with eusocial insects”, Insectes Sociaux, August 2000, Volume 47, Issue 3, pp 201-211
[2] If they are overwintering, then they stop before pupating and go through the winter in the bee nest as a “pre-pupa”.
[3] The males look nothing like the females, they are little black wasps that fly around. For a lot of the velvet ant species, the males have not yet been identified, since you pretty much need to either catch them in the act of mating or rear the eggs from a known mother to really see which male goes with which female.
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Have chased many of the larger velvet ants trying to get a pic. They seem to be in constant motion. Didn’t realize they were parasitoids. Good info.
These little, nearly hairless ones that we have up here aren’t particularly quick. They walk maybe half as fast as the average comparably-sized ant. I expect that they probably move a lot faster in warmer climates, though.