Flight motor activity of houseflies as affected by temperature and insecticides

Muscle potentials recorded extracellularly from one pair of fibers of the dorsal longitudinal flight muscle in the housefly, Musca domestica L., show a very regular pattern with both pairs driven in alternating sequence. Houseflies with chronically implanted electrodes activated the flight muscles without externally observed motion, either walking or in flight, in apparent shivering responses. The frequency of activation of the flight muscle in shivering was temperature dependent below 25°C with Q10 of 2.57. No shiver was recorded above 26°C. During insecticide poisoning, both gross locomotory activity and flight muscle activation first increased, then decreased slightly, then gradually increased again to a condition of tetany. After treatment with lethal doses of peripheral nerve poisons such as DDT, and pyrethrin analogs, the flight muscle activity pattern gradually increased in tetany and was constantly active for several hours. When poisoned with central nervous poisons such as lindane, dieldrin, endrin, and organophosphorus and carbamate anticholinesterase poisons, the post-tetanic period of poisoning was characterized by discrete bursts of motor unit activation interrupted by inactivity. The high-frequency spasms of flight muscle activity during poisoning resembled hyperactivity obtained due to overheating of houseflies.