A fierce preda­tor with lit­tle red feet

Meet one small bug-eyed mon­ster, the red-footed can­ni­balfly

Rappahannock News - - FRONT PAGE - PAM OWEN wil­[email protected]

Although many in­sects have wound down their re­pro­duc­tive ac­tiv­i­ties, some are still go­ing at it, or just get­ting started, in­clud­ing one small bug-eyed mon­ster, the red- footed can­ni­balfly. Hear­ing loud buzzing around my head on a cou­ple of oc­ca­sions, I thought bees were fight­ing near my head only to turn around and see two large, hairy flies with an en­tirely dif­fer­ent agenda on their minds. They were red-two footed can­ni­balflies ( Pro­machus ru­fipes), in the rob­ber fly fam­ily ( Asil­i­dae), work­ing on pro­duc­ing next year’s gen­er­a­tion.

Re­lated to drag­on­flies, rob­ber flies not only look fierce but are fe­ro­cious in their hunt­ing. Also known as as­sas­sin flies, they of­ten take on prey that are al­most their size — or even big­ger than they are. In try­ing to learn more about the fly’s re­pro­duc­tion, I ended up on the Hil­ton Pond Cen­ter for Pied­mont Nat­u­ral His­tory web­site (hilton­pond.org/ThisWeek07­0901.html). Although the cen­ter is in South Carolina, many of the same species are found in Vir­ginia’s Pied­mont, and I’ve of­ten found great in­for­ma­tion for this col­umn there.

As the web­site’s “This week at Hil­ton Pond” blog for Sept. 1- 7, 2007, notes, “rob­ber flies make up one of the big­gest and most widely dis­trib­uted in­sect groups in the world, with more than 7,000 species — some dat­ing as far back as the Eocene Epoch (54.8 to 33.7 mil­lion years ago).” While I didn’t get much info on the red- footed’s breed­ing habits, I did find some tes­ta­ment to its fe­roc­ity.

Rob­ber are among the few preda­tors that are quick, strong and big enough to catch a hum­ming­bird, with a few in­ci­dents cir­cu­lat­ing through sev­eral na­ture-re­lated web­sites, in­clud­ing Hil­ton Pond’s. The red- footed can­ni­balfly, in the “gi­ant rob­ber fly” genus ( Pro­machus ), is 1- 1.25

inches long, about half the size of most hum­ming­birds. The blog de­scribes ac­counts of hum­mers be­ing nailed by this rob­ber fly as well as one in the “bee killer” genus ( Mal­lophora), the beelze­bub bee- eater ( Mal­lophora leschenaul­tia). Bees are a fa­vorite prey of rob­ber flies. The other com­mon name for the red- footed can­ni­balfly is “bee pan­ther.” Some rob­ber flies in the Mal­lophora genus have ac­tu­ally evolved to mimic bees, en­abling them to sneak up on their prey.

Ac­cord­ing to the web­site of the Univer­sity of Florida’s en­to­mol­ogy depart­ment (tinyurl.com/wi-uf-flies), rob­ber flies grab their prey in flight, in­ject­ing their vic­tims with saliva that has par­a­lyz­ing and liq­ue­fy­ing en­zymes. “This in­jec­tion, in­flicted by their mod­i­fied mouth­parts (hy­pothar­ynx), rapidly im­mo­bi­lizes prey and al­lows di­ges­tion of bod­ily con­tents,” the site says. Although rob­ber flies, like drag­on­flies, have no in­ter­est in us beyond per­haps us­ing us as a perch oc­ca­sion­ally, they have the equip­ment to in­flict a nasty wound if not han­dled care­fully, so are best left alone.

I was first in­tro­duced to red-footed rob­ber flies a few sum­mers ago when I found one feed­ing on a cor­eid bug, which was al­most the same size as the fly, from a perch on one of the gi­ant sun­flow­ers I planted next to my house. I was re­ally drawn to the fly be­cause of the jux­ta­po­si­tion of its fiercer fea­tures — the hairy, tough, tiger-striped body, humped back, bulging black eyes and long, spined legs —against two mit­ten-like red “toes” at the end of its legs. The lit­tle mit­tens bely the whole bug-eyed mon­ster look this fly is oth­er­wise rocking.

Those long, strong legs also play a role in courtship, which hap­pens around this time of year. Rob­ber flies’ courtship be­hav­ior is far from ro­man­tic, with the male pounc­ing on the fe­male “much like an act of prey ac­qui­si­tion,” ac­cord­ing to the FL web­site. The pair I men­tioned above that were buzzing around my head were in the process of the next re­pro­duc­tive step — cop­u­lat­ing tail-to-tail, with the male and fe­male gen­i­talia in­ter­locked. This is sim­i­lar to how drag­on­flies, which are in the same or­der (Odo­nata), mate. (See a shot of grounded red-foot­eds mat­ing at the What’s that Bug web­site, tinyurl.com/wi-can­ni­balfly).

Also like drag­on­flies, rob­ber flies can mate while in flight. The next day I spot­ted an­other pair on my gold­en­rod. The male was on the back of a fe­male, grasp­ing her with his legs.

Ac­cord­ing to the UF web­site, fe­male rob­ber flies de­posit their eggs on low­ly­ing plants and grasses, or in soil, bark, or wood. Their lar­vae live in the soil or in var­i­ous de­cay­ing or­ganic ma­te­ri­als and are also preda­tory, feed­ing on eggs, lar­vae or other soft-bod­ied in­sects. Rob­ber flies over­win­ter as lar­vae and pu­pate in the soil. Pu­pae mi­grate to the soil sur­face, even­tu­ally emerg­ing as adults. It takes one to three years for the fly to de­velop into an adult, de­pend­ing on the species and en­vi­ron­men­tal con­di­tions. For more in­for­ma­tion about the many species of rob­ber flies, in­clud­ing lots of pho­tos, go to BugGuide.net (bugguide.net/node/view/151).


De­spite its name, the color of a red-footed can­ni­balfly’s feet can vary from bright red to or­ange or tan.


Rob­ber flies have rough courtship, with males grab­bing fe­males just like they do prey, be­fore they mate tail-to-tail. Right: Red-footed can­ni­balflies will not only prey on large in­sects such as this cor­eid bug, as well as bum­ble­bees and drag­on­flies, but are also known to go af­ter hum­ming­birds.


A new video shows how to make a frog pond to at­tract anu­rans such as this wood frog.

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