louiseinva's Favorites

Male, one of three individuals feeding on a few clumps of Asclepias incarnata in the vicinity.

This individual is likely the freshest of the large Tachytes that I've seen, with intact wing margins and beautiful long golden hair on the propodeum and anterior face of tergum 1.

I think, working with Bohart 1994 again, that this is either T. crassus or T. harpax (two of the species in the ermineus group), although the ID even to that level is tentative, pending getting some more details on the identification issues.

First, it clearly has erect pale hairs under the hind femur (image 1 shows this best, but some of the others support it as well). If you haven't tried it, you should know that getting a shot that shows hairs there is difficult: the angle and the light have to be just right.

Second, the scape seems to be black (images 6 and 9) and the base of the mandible seems to be black as well (or at least not red): see image 9.

The combination of mostly black hindfemur and red hindtibia, then, according to the key, screens the possibilities down to the two species mentioned above.

It appears that flagellomeres 2 through 5 are moderately convex beneath, which might be compatible with either species (as well as others). T. harpax is supposed to have the stronger convexity.

I'm still trying to find out more about the lateral and/or apical hair tufts mentioned in the key. The key does not mention the long hair on the propodeum and tergum 1 (one way or the other), nor does it mention the silvery hair on tergum 7 (for views of the tip of the abdomen, see images 3, 4, 7 and 8).

The key does indicate that one of the differences between the two species is the presence or absence of a patch of reflective setae anterolaterally on the scutum. I think that feature is present here, which is supposed to be the state shown by T. harpax (but not T. crassus). See images 2, 5 and especially 6.

Finally, note that Heather Holm, in her book Wasps, mentions the lack of conspicuous spines on tarsomeres 1-4 on all six legs of T. crassus; I'm not entirely sure if the current wasp qualifies as having non-spinulose tarsi, but I will say that I have recently edited images of Tachytes that had considerably more spines on the tarsi than displayed by this individual.

For a similar wasp, which I have very tentatively identified as T. crassus, please see: https://www.inaturalist.org/observations/202343529