Size
Large flies, typically bumble bee size.
Habitat
Habitat is less important to these flies than the host mammals. Habitat-specific rodents or rabbits means habitat-specific species of bots.
Life Cycle
Females typically deposit eggs in the burrows and "runs" of rodent or rabbit hosts. A warm body passing by the eggs causes them to hatch almost instantly and the larvae glom onto the host. The larvae are subcutaneous (under the skin) parasites of the host. Their presence is easily detected as a tumor-like bulge, often in the throat or neck or flanks of the host. The larvae breathe by everting the anal spiracles out a hole (so they are oriented head-down inside the host). They feed on the flesh of the host, but only rarely does the host die as a result.
Remarks
Larvae are common. George "Jeff" Boettner tells of live-trapping rodents where up to 80% of the populations had bot parasitism. Adult flies are almost never seen, though in western North America the males are known to "hilltop" from about 9 AM until noon on isolated buttes in arid habitats.
