Wednesday, April 3, 2013

Promachella pilosa, a new genus and species for BugGuide and the UAIC

Every morning during breakfast on the patio we sneeze at all the pollen that drift over from blooming Creosote and Brittle Bushes. We both have been in Arizona long enough to develop pollen allergies. While Randy so far just sneezes, I experience the whole spectrum from itchy eyes to sinus problems. But eventually I will jump up with my camera that sits always next to my coffee cup to get even closer to the flowers (I very much appreciate that my point and shoot camera has no view finder. While this seemed to be a serious draw-back at first, it now saves me from getting my face right into the blooming bushes.)
Most of the insects are arriving to either collect pollen and/or nectar, find mates, eat parts of the flowers or leafy parts or deposit their eggs so their off-spring can do so. A few spread their eggs so their off-spring can hitch rides on other flower visitors to  become a parasitic guest in their nurseries.
And of course this aggregation of spring insects also draws some predators.

Promachella pilosa female
 Yesterday I observed a robberfly that was feeding on a small bee. She was busy and easy to approach so I got some good photos. In shape and coloring she reminded of the genus Promachus, but at less than 15 mm she seemed small.

Promachella pilosa male
 Not much later I found a similar, but even smaller male. He was shyer and kept landing among the branches of a Creosote bush, so his portrait didn't turn out quite as well.
On BugGuide Dr. Eric M. Fisher a Diptera specialist with special interest in Asilidae identified
my patio robbers as Promachella pilosa. I am rather proud to say that this added a new Genus and species to Bugguide. Checking the online species data base of the UAIC, I found that there are no (identified) specimens in the collection either.
While it is nice to photograph something new and special (I found no other photos on the web) there is not much information out there either. I have no access right now to Willcox original 1937 paper. So all I know so far is that this is a fly that is only known from Arizona and from neighboring Sonora, Mexico. 
But since the appearance is so similar to that of the widespread genus Promachus, and the female is lacking the dagger-like ovipositor of some genera that stick their eggs into plant material, I guess that the females of the genus Promachella deposit their eggs into the soil. 


  1. I have never seen a Robber Fly before and I sat with my mouth gaping open in shock for a few minutes before reading your post. They look like a mixture between a Dragon Fly and a big hairy spider. What an amazing beast. Congratulations on having it added to the bug guide!

  2. I love robber flies. My dad showed me my first one when I was probably 8 or 9 in south-central Oregon. How exciting to add a totally new genus to Bugguide – that's not so easy these days.