Asilidae : Other Arkansas Robber Flies

This member of the Leptogastrinae is Leptogaster murina. It is best identified by habitat. It occurs in prairie remnants and open meadows of calf- or knee-high grass. Look for the tiny thread-like creatures moving low down in the grass, usually in places where the grass is a bit sparse, so that small patches of bare ground are showing through. They occur in colonies, so where you see one, you can probably find a few more. Through your binoculars they will appear plain brown, with unmarked yellow-brown legs. I find them in early summer in grassy prairies or meadows in the Ozark and Ouachita Mountains.

Despite the death's-head pattern on the thorax, and the hornet-like coloring, this Laphria saffrana is much more charming than threatening. It is tame and even friendly appearing, landing on your boot-top or pant cuff to ride along with you as you are walking. It is identified by the fact that nothing else is remotely like it. Like all Laphriinae, it lays its eggs in wood, in this case rotting pine logs, and is found in open forests predominantly of pine trees. It is fairly common in the western part of the state.

A member of the Stenopogoninae, Eudioctria tibialis is a tiny fly that looks like one of the twig-sitting dots, rather like Cerotainia without extra-long antennae. But a very important distinction is, it does not perch on twig-ends, but persistently lands on flat leaves at the top of small shrubs. I have found these in pine-oak woodland edge in the southwestern part of the state.

To go to another extreme, this Hadrokolos texanus vies with Townsendia nigra as the smallest robber fly in the state. This particular male is 3.3 mm long. It's a unique record for the state. We found it at the beginning of September. We were on the eastern shore of Lake Norfork when my sharp-eyed wife saw a tiny dot perched at the end of a twig fly out, then return to its perch. I caught it for that reason, but wasn't convinced it was a robber fly till I had it under the microscope. The identifying character here for Hadrokolos is that the male genitalia face forward.

Holcocephala calva, a twig-sitting dot, is very similar to Holcocephala fusca (which see), and is found in the same riparian habitats, but is a bit bigger, a bit longer in body, and the abdomen has a distinct hourglass shape, being pinched in in the central segments.

Proctacanthus rufus is an all-red Proctacanthus, looking exactly like P. hinei (which see). The external genitalia on the males differ enough in the two species that they are easily distinguishable through binoculars, but the females (as here) are not separable. They are best identified through habitat, P. hinei on bare sandy river beaches, P. rufus in slow-moving heavily vegetated marshy areas of streams.

Here is Machimus antimachus. It is a common species but confined to the western half of Arkansas, so I don't see it very often, and I am not very familiar with it. It seems to share a lot of features with Philonicus rufipennis (which see), particularly the long wings and the red or pale brown femora with usually a smudge of black on the outer side. It seems to be paler than Philonicus, with whiter sides and a fuller white mystax.