The Robber Flies of Crowley's Ridge, Arkansas

An Illustrated Field Guide by Norman Lavers

Asilidae : Laphystiinae

Species of Crowley's Ridge

The Laphystiinae are generally very small flies with strongly banded abdomens. Three species in two genera occur along Crowley's Ridge. The individual here is doing what Robber Flies almost never do, and that is, landing on flowers. It's probably just a coincidence, but it makes you wonder if it is pretending to be an innocent bee, waiting for some unsuspecting tinier insect to arrive.



Laphystia ochreifrons

The first species is Laphystia ochreifrons, a pretty, 8 mm-long fly, that occurs, often in numbers, on the sandy shores of rivers, with lots of male-chasing-female activity. I recently found about a dozen of these on the wet sand at the bottom of a boat launch in a park in the town of St. Francis, on the shore of the St. Francis River. If they had been 40 feet farther north, they would have been in Missouri, and I wouldn't have been able to include them.


The various species of Laphystia are identified by the pattern on the abdomen, but there is only this one species, ochreifrons, we have to deal with on Crowley's Ridge. So look for a small, active robber with big eyes and a strongly marked abdomen at water's edge on an open sandy beach. They will probably be accompanied by similar looking, somewhat larger Bronzed Tiger Beetles. (Caution: See Stichopogon trifasciatus below, a robber with similar behavior and habitat, but with one very obvious unmarked segment in the abdomen.)



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Psilocurus birdi

Psilocurus birdi is another small fly in the Laphystiinae. It's only a little larger than an Atomosia. You will find it, in mid-summer, either on the poison ivy leaves in woodland, or in tall grass in a field. The best mark is the plump-appearing bee-like banded abdomen.


These tame little flies often appear in a blackish form.



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Psilocurus nudiusculus

The final species in this subfamily, Psilocurus nudiusculus, is even smaller, and is perhaps best identified by its habitat. I find it near water in bottomland woods on bare sand or silt with scattered grass or other low sparse vegetation. A very small robber landing on or near the ground on, say, a path next to a swamp or canal, will likely be this species. Depending on the light, the eyes often appear bright green.


The male of P. nudiusculus is smaller still, with a bit more marking on the abdomen. He often makes a hovering courtship flight before the female, rather like Atomosia puella.



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