MOBILITY OF 3 GENERALIST PREDATORS IS GREATER ON CABBAGE WITH GLOSSY LEAF WAX THAN ON CABBAGE WITH A WAX BLOOM

Adult coccinellids Hippodamia convergens Guerrin-Menneville, adult min ute pirate bugs Orius insidiosus (Say), and larval lacewings Chrysoper la carnea (Stephens) have been reported to more effectively reduce pop ulations of Plutella xylostella (L.) (Plutellidae: Lepidoptera) larvae on a cabbage with glossy surface waxes than on a standard cabbage var iety. To examine the mechanisms, the behavior of each predator species was quantified on the two cabbage types. All three predators spent le ss time walking on the standard variety and more time in other activit ies, including grooming and 'scrambling' (ineffective forward locomoti on). In addition, walking by each predator was distributed more evenly among the parts of the leaf on the glossy cabbage than on the standar d variety. In small enclosures, C. carnea and O. insidiosus found and attacked individual first instar P. xylostella more quickly on the glo ssy cabbage. Scanning electron micrographs showed debris, probably wax , on the tarsae of C. carnea and O. insidiosus that had walked on the standard variety, but not on those that had walked on glossy cabbage. H. convergens tarsae did not accumulate debris on either cabbage type. predator mobility and effectiveness were apparently impeded by wax cr ystals, which are present only on the standard variety. This mechanism can explain the greater effectiveness of these generalist predators a gainst P. xylostella larvae on glossy vs normal-wax cabbage.