Effects of Insecticides on Spiracle Movements in Insect

We studied the effects of permethrin and DDVP on thoracic spiracle movements of the male cockroach. Permethrin increased, rather than decreased, the average open time of thoracic valve 1 in low or lethal doses, with no large change in the frequency of the opening and closing. In thoracic spiracle 2, the average open time was reduced by 1/3 of the control, but the opening frequency was markedly increased. DDVP had a similar effect on thoracic spiracle 1. The action of DDVP was only transiently and partially antagonized by atropine. These results suggest that the thoracic spiracle 1 valve tends to open, probably by a peripheral control mechanism, rather than to close, during permethrin or DDVP poisoning in insects