A technique is available for individual marking and measurement of these tiny live flies without injury (Bonduriansky & Brooks 1997). Flies are marked on the thorax with enamel paint. Here's a video of a marked antler fly male on a moose antler. Because males tend to spend every day of their lives on the same antler, it is possible to observe them throughout their lives and obtain biographical field data on their behaviour and life history. Their 2-hour long copulations make it possible to estimate mating success in the field.

This unique species has provided the first evidence of ageing (senescence) -- declining survival rate and reproductive rate -- and its fitness costs in an insect population in the wild (Bonduriansky & Brassil 2002). Our analysis also showed that ageing rate is related to body size: large males exhibit faster reproductive ageing than small males (Bonduriansky & Brassil 2005). Research on these tiny flies is continuing through a collaboration with Howard Rundle's lab at the University of Ottawa.

Male antler flies are astonishingly aggressive: litigata translates roughly as 'bellicose'. On antlers, males form complex, highly structured aggregations. Some individuals defend stable territories, while others simply wander in search of females, which arrive on antlers to feed, mate and oviposit (Bonduriansky & Brooks 1998, 1999). In prime areas of the antler, near oviposition sites (cracks in the antler surface), males spend much of their time battling rival males. They even attack insects vastly larger than themselves. This video of an antler fly aggregation was created by Phil Savoie of the BBC-NHU. The photos below show male-male combat.

Antler flies appear to engage in mutual mate choice, with both males and females rejecting some potential mates (Bonduriansky & Brooks 1998). Following copulation, the female expels and ingests much of the male's ejaculate, then inserts her ovipositor into minute cracks or pores in the antler surface and deposits her eggs. During oviposition, the male remains on the female's back and 'guards' her by warding off rival males with his wings (Bonduriansky & Brooks 1998b). Mating and ovipositing pairs are viciously attacked by single males, who attempt to dislodge the male and re-mate with the female (bottom left photo). Sometimes, several single males attack a female simultaneously (bottom right photo). Such wrestling matches can last for several minutes, and females and males can sustain serious injury.

Antler flies face a wide array of predators on antlers, such as the lacewing larva (left) and spider (right) in the photos below. A predatory empidoid fly with raptorial forelelgs (Tachypeza sp.) also attacks antler flies. 

Antler flies are also exploited by mites, which sometimes undergo explosive outbreaks lasting several days. Some antler fly individuals have nematode parasites in their abdomens. The photos below show a male heavily infested by mites and missing part of one fore-leg (left), and a female with mites all over her abdomen being mounted by a male (right).

Antler fly larvae develop in the porous bone matrix inside antlers, and come to the antler surface when ready to pupate. Here, the larvae perform an astonishing leap off the antler surface, as seen in this video. They land on the surrounding leaf-mould, burrow into the soil, and undergo metamorphosis. The photos below, showing an antler fly maggot preparing to leap, were created from footage shot by Phil Savoie, BBC-NHU. The sequence is shown from left to right, and top to bottom: the maggot first raises the anterior part of its body and curves it into a loop, then grasps its posterior end with its mouth-hooks, and tightens its muscles to create tension; finally, the maggot releases its hold abruptly (not shown here), causing its posterior end to recoil against the substrate, and launching itself into flight.