LABORATORY STUDIES OF PREDATION OF GRASSHOPPER EGGS, MELANOPLUS BIVITTATUS (SAY), BY ADULTS OF TWO SPECIES OF PTEROSTICHUS BONELLI (COLEOPTERA: CARABIDAE)

Abstract In two-choice laboratory feeding trials in Petri dishes, adult carabid beetles, Pterostichus corvus (Leconte) and Pterostichus femoralis (Kirby), ate a higher percentage of grasshopper eggs, Melanoplus bivittatus (Say), than of cat food. Pterostichus corvus ate more eggs than did P . femoralis . Grasshopper eggs buried in soil in terraria were eaten by P . corvus adults at more than twice the rate of eggs exposed on the soil surface; predation rates at depths of 2.5 and 5 cm were the same. In plant-propagation trays, predation by P . corvus of buried grasshopper eggs was studied under three types of ground cover: Nicotiana seedlings, with rosette-form growth habit; barley seedlings, which exhibited upright growth; and bare ground. A significantly higher percentage of eggs was eaten under the Nicotiana than beneath the other types of ground cover, and predation rates did not differ between the barley and bare-ground treatments. Pterostichus corvus appears to be a suitable candidate for enhancement of natural biological control of grasshopper eggs, and manipulation of vegetation cover in grasshopper egg beds may be an effective technique for enhancing predation rates.