Taxonomy and Life History of the Moose Fly, Haematobosca alcis and Its Association with the Moose, Alces alces shirasi in Yellowstone National Park

The moose fly, Haematobosca alcis (Snow) is abundant in Yellowstone National Park wherever its host, Shiras' Moose, occurs. Descriptions of the 2nd and 3rd instars, the puparium, and both sexes are given. H. alcis is similar morphologically to its European congener, H. stimulans , but can be distinguished particularly by size, biology and host preference. Except for the difference in host specificity, the biology of H. alcis is similar to that of Haematobia irritans . The females oviposit in fresh moose droppings, depositing about 10 eggs each 0.5-3 min after a moose defecates. Development from egg to adult requires about 16 days at 21°C in the laboratory. Flies emerge from overwintered pupae in late spring (usually early June) and adults are active until late September. The haematophagous adults are host specific for moose and remain with the host animal, except when females are ovipositing. Occasional specimens were attracted to horses when near moose habitat and one male attempted to pierce the skin of man. Moose did not appear particularly annoyed by H. alcis , even when 500 or more flies were present/animal.