ABUNDANCE, WINTER SURVIVAL, AND SPRING EMERGENCE OF FLEA BEETLES (COLEOPTERA: CHRYSOMELIDAE) IN A MANITOBA GROVE

Abstract

AbstractAdult flea beetles, Phyllotreta cruciferae (Goeze), P. striolata (F.), and Psylliodes punctulata Melsh., overwintering in the litter of a riverbank forest at Winnipeg, Manitoba, varied in density from about 1.4 million to 2.5 million beetles per hectare from 1979 to 1983. Phyllotreta cruciferae was the most abundant species (78–92%) and P. striolata next (6–22%) in litter samples collected in the late autumn, just before the ground froze. The distribution of beetles was highly aggregated (variance/mean ratio > 1.0) for P. cruciferae and P. striolata in years of high density but this ratio was 1.0 (random distribution) when densities were below 1.0 per square metre. Density was positively related to the amount of litter and increased from the edge to the center on the south side of the grove. On the north side, densities were highest at the edge of the grove. Survival in the litter during the autumn was generally lower and more variable than during the winter or spring periods. Survival in the litter during the 4 years ranged from 0.22 to 0.46 for P. cruciferae and from 0.31 to 0.83 for P. striolata. Temperature, through its effect on the time of emergence of adults in late summer and autumn, may affect their ability to survive the onset of cold weather.