PREDATION ON ADULTS OF THE FLEA BEETLE PHYLLOTRETA CRUCIFERAE BY LACEWING LARVAE (NEUROPTERA: CHRYSOPIDAE)

Abstract

Several instances of predation by lacewing larvae on adults of the flea beetle Phyllotreta cruciferae (Goeze) have been observed in Saskatchewan. Other reported insect predators of rapeseed-crop-infesting flea beetles in the Canadian prairie provinces are the beetle Collops vittatus Say (Gerber and Osgood 1975), and one of the big-eyed bugs, Geocoris bullatus (Say) (Burgess 1977).The first observation of an attack on an adult flea beetle by a lacewing larva was in August 1972, when some lacewing larvae, adult flea beetles, diamondback moth larvae (Plutella xylostella (L.)) and unidentified aphids and midges were swept from maturing rapeseed near Aberdeen, Saskatchewan. One of these lacewing larvae attacked an adult of P. cruczferae in a glass collecting-vial and carried the flea beetle around in its jaws. Other lacewing larvae attacked aphids, midges, and diamondback moth larvae. Further evidence for lacewing larvae feeding on adult flea beetles was obtained in August 1979, when a sizeable population of lacewing larvae in a rapeseed crop was encountered near St. Gregor, Saskatchewan. One of the larvae swept from this crop had an adult of P. cruciferae in its jaws when it was first seen in the sweep net. Later the same day, another lacewing larva, swept from a nearby rapeseed field, attacked an adult of P. cruciferae in a collecting vial. In the laboratory both lacewing larvae, still carrying their prey, were quick-frozen, preserved in 70% ethanol and later photographed.