A Method of Testing Insect Traps and Attractants, and Its Application to Studies of Hippelates pusio and Culex tarsalis1

Abstract

A test developed by the author to compare baits attractive to the eye gnat ( Hippelates pusio Loew) has also proved useful in investigations of Culex tarsalis Coq., both in studies of the avian hosts of this mosquito (previously reported) and in the evaluation of different traps. The basic feature is the slow rotation around a central point, at a fixed radius and in a horizontal plane, of identical traps containing different baits, or of different traps containing identical baits. The apparatus used for this purpose is called a rotary. The advantage of the method derives from its reduction of site differences. When, in accordance with a Latin-square design, each bait is tested in each trap in a multiple-period test, it is possible, through analysis of variance, to evaluate separately the effects of baits, traps, and periods of test. If one element (baits or traps) is found not to make a definite contribution to total variance, other designs become available. Similar apparatus and tests have been developed and used by other workers, the first of whom was apparently D. E. Eyles. Use of rotary testing has shown that, upon exposure to air, liver bait for H. pusio becomes more attractive over a period of 1 or 2 days, that exposure to air does not increase its attractiveness to Hippelates bishoppi Sabrosky, that bait which putrefies under aerobic conditions is more attractive to H. pusio than bait matured anaerobically, and that the liver bait used in the writer's studies was more attractive to H. pusio than an egg bait originated by E. R. Tinkham. In tests of CO2-baited traps for C. tarsalis, those of larger size were found more efficient, and no baffle was found superior to a round entrance at the apex of an inwardly directed cone of wire screening.