Determination of Parasite Preference by Choice Tests: the Aphidius smithi (Hymenoptera: Aphidiidae)-Pea Aphid (Homoptera: Aphididae) Model

Publisher Website
Google Scholar
Abstract
Some problems associated with the use of choice tests for assessing parasite preference are examined. When provided with equal numbers of 24-h-old (“test” = T) and 96 h-old (“Standard” = S) pea aphids, the hymenopteran parasite Aphidius smithi Sharma and Subba Rao prefers the older S-aphids. Three variables are compared as possible estimators of preference; assessment based on the total number of hosts attacked in each class is recommended. A functional relationship is demonstrated between the length of the parasite's searching time and the total number of hosts attacked, as well as the proportion of T hosts attacked. The difference between the number of T and S hosts attacked declines with test duration. Equations are provided for estimating the critical time at which preference can no longer be detected experimentally. The best estimate of A. smithi preference, taken near the time of maximum deviation of the observed from the expected attack rate, is 0.246 T/S, with 95% confidence limits of 0.173 and 0.350.