This robber fly was one of those that I actually remembered from the year prior and I was waiting to catch one this past year to find out what it was. I had recalled that instead of the fat Laphria antennae it had a thin wispy one. Note that it is a big bumblebee mimic like Laphria. I personally think it is an even better bumble mimic than most Laphrids.

I have watched these now in heavily flowered areas around bumblebees to clarify the question of whether the mimicry is there to improve bumble predation or to protect this robber from other predators that may avoid bumblebees. And I can say that I have yet to see this robber, Mallophora orcina, take a single bumblebee. I did see one knock one down and abandon the effort. And saw another try to take another Mallophora with equal ineffectiveness. Lavigne's database of prey and predator records quite a few bumblebee, honeybee, wasp and yellow jacket kills for this species. I will just have to watch longer I suppose.

When I caught this animal I had hopes it might be the Holy Grail of robber flies, Dasylechia atrox. Dasylechia also has the bumble look and also has a thin antennae. Mallophora has wing veins like a Promachus  (see the Fritz-Geller robber link for anatomy schooling) which was astounding to look at on this bumble creature.

Dasylechia is a genus with a single robber species and it is a very primitive one apparently. At present there have been only thirteen collected in all of North America. Most of these are from Ohio. But also as far away as Iowa and Utah. Obviously, the distribution is poorly known, not to mention the biology. Described in 1884, the only Michigan specimen (in the excellent Michigan Robber summary paper from 1975) was taken in 1888. I'll keep looking, I guess.

In July of 2005 I received an email from a Biologist at the Balcones Canyonland's NWR in Texas. A local gardener had some 'giant flies' emerging on her property. She described them as being 'fairly common' as they emerged from her compost heap. She apparently even had the pupal cases of some of them. She turned some over to the biologist, Chuck Sexton, who proceeded to key them to Mallophora after recognizing that they weren't just any flies, they were robber flies. This is no small feat, keying in the big eastern genera key without some fly experience. Maybe he had some. But this is indeed Mallophora leschenaulti, one of the largest Asilids in the US. This is a scan and not a photo but I brightened it up for improved viewing (thanks to Gayle Strickland for further photoshop enhancements).

Interestingly, here is what Bromley had to say in his Robber Flies of Texas paper from 1934 about what was then known as Mallophora belzebul:

This huge species is represented in Texas in the U. S. National Museum by
three specimens: Uvalde, 1917, (D. C. Parman); Concan, 1910, (F. C. Pratt);
and Sonora, 1924, (O. G. Babcock) (J. M. Aldrich). Under date of March 26,
1927, Mr. D. C. Parman wrote me that specimens collected on July 17, 1917,
were taken by a ranchman: "For the last week large numbers of the flies have
been emerging in a goat pen. They have never been seen except early in the
mornings and have never been observed to fly (supposedly they have just
emerged as there were several pupae cases in the lot brought in). The
ranchman stated that ground was covered in the goat pens as large as a room
15x20 ft. He is an old settler here and he and his neighbors have never seen
the fly before...The specimens were all taken near Montel. It was
interesting in that several other species commonly found in Mexico and S.
America were found here in 1917. It was thought that they were brought in by
a tropical storm in August, 1916." The specimens were identified by Mr.
Frederick Knab at the National museum. Chisos Mts., Brewster Co., July 19
(Duncan) (F. R. Cole).

And from Nancy Radding, a master naturalist in the Austin area this info:

she actually lives in the south part
of Austin, Texas, in a residential neighborhood in town.  She said these
flies are common in a large compost pile in her yard.  The compost is
primarily made up of leaves of pecan trees with a small proportion of
household vegetable scraps.  The leaf pile is usually about 8 ft x 12 ft
and, in the fall, starts off a few feet thick before it "cooks down" by the
following summer.

She first recalls seeing the Bee-killers emerging in 2003.  She wasn't home
in the summer in 2004 to notice them.  This year, the emergence started
about June 23-25 and continues to this week so far.  The emergence only
lasts a few weeks.  Dozens of the flies have emerged from the compost,
sometimes 9 to 12 at a time.  Most emerge in the morning hours but they may
emerge any time during the day.  Typically, the pupae "wiggle" up and out
of the leaf pile and rest on top for a time, presumably drying out and
gaining thermal energy.  The adult flies emerge and rest quietly by the
pupal case for awhile before flying off.  At those times, they are easily
handled.
 

Interesting that some of these may have been storm borne from south of the border. Impressive insects. It is more likely that the imported pig maneur or compost in the first site was the method of import. I vote for Belzebul's Bee-eater as the common name.
 

This is a shot I had previously taken in the Austin area by John Ingram. I believe it is the free-flying adult of this same giant. Texas has a third species of Mallophora that is slightly smaller than M. orcina and is brownish.

In July 2005 I heard from another Austin Texas resident  who communicates with the name larvalbug for her internet activities. She also has the monster Mallophora in her yard. They were reemerging in July of this year. But she had shots of this egg-laying activity from 2004. This is the first time I have seen any Asilid with an eggmass associated with its eggs. The rest have just soil dispersed (Diogmites) or implanted eggs in plant stems or flower heads (Promachus and various Efferia).

Here is the completed egg mass. And apparently the 'hatchlings' have either a long way to fall or they must crawl to the soil at some point. This is unknown.

This is a pupal case post emergence from larvalbug's yard.

And her very fine adult shot.

Her description:

"I'd sort of forgotten about these robber flies until this morning (2005), when I went out to hang up some laundry. I found 3 that had just emerged from our lawn. This is where they are easiest to find, since they are pretty obvious against the grass and are still slow because of having just emerged. I can almost always find their pupa shells. They have a hard time getting airborne, but I simply pick them up and hold them several feet off the ground and they fly away with no trouble. As your page states, they are monster flies - I've never seen any as big and was at first rather startled when I encountered them. I've never seen them catch any prey, but I did see one female lay eggs last year..."