The life history and bionomics of the red deer warble fly Hypoderma diana (Brauer)

(1) The oesophagi of five deer were stripped and inspected but no larvae were present. (2) Forty -seven carcases were split and the spinal canals examined, but there was no sign of larvae, nor any trace left by the larvae in the epidural space. (3) i igrating first instar larvae were encountered only under the skin and between the muscles, and by plotting their respective positions on various carcases throughout the season, their route could be established. it was suggested that the eggs were laid on the lower parts of the legs, the forelegs being chosen in preference to the hind legs. After the larvae hatch out and burrow into the skin, they remain in these lower parts for some time before moving towards the back. From the forelegs, their route takes them up over the shoulders towards the spine and then in a posterior direction to assume their position along the flanks. Those on the back legs move over the thighs and then anteriorly to the flanks. This migration requires almost six ilonths, at the end of which time the larva moults to the second instar. (4) The second and third instars are non -migratory and develop in the one position under the skin. The second/ - 54 - second instar larvae moults after about six weeks, the third instar larvae being found from the end of January onwards. () The third instar larvae may mature in one month. As they develop they change in colour from white, through yellow and brown to black, and the integument becomes leathery and waterproof to withstand the variable conditions without the host. (6) The larvae emerge and pupate on the ground in two to nine days. (7) Flies emerged in the laboratory in three to four weeks. They are actively ovipositing during May and June. (8) The behaviour of adults in captivity is described. They do not feed and their life span is restricted. (9) The sex of the host and its acquired resistance governed by its general condition, affect the development of the larvae. The grubs may be parasitised by a fungus. Climatic conditions and their effect on the various stages are discussed. (10) Deer movement is shown to have an effect on the resulting infestation of warble larvae.