Density and Survival of Lady Beetles (Coccinellidae) in Overwintering Sites in Manitoba

Abstract

The densities of lady beetles, Coccinellidae, overwintering as adults (adults per m²) in leaf litter collected in late October for two years in a beach-ridge forest on the south shore of Lake Manitoba were 56.4 for the Thirteen-spotted Lady Beetle, Hippodamia tredecimpunctata (Say), 38.3 for the Seven-spotted Lady Beetle, Coccinella septempunctata (L.), 7.7 for the Transverse Lady Beetle, Coccinella transversoguttata richardsonii Brown, 1.6 for the Convergent Lady Beetle, Hippodamia convergens Guerin, and 0.6 for the Parenthesis Lady Beetle, Hippodamia parenthesis (Say). The mean overwintering survival for these species was 0.254, 0.036, 0.023, 0.0, and 0.0, respectively. The density of overwintering coccinellids was highest near the margins of the forest, particularly on the beach side, where beetles from shore appear to have entered the forest. The mean density over 3 years (2.9 per m²) of all coccinellid species in November in the litter under a remnant grove of riverbank forest in Winnipeg, was lower than in the beach-ridge forest (104.8 per m²), but their survival (0.460) was higher than in the beach-ridge forest (0.154). More species of coccinellids were found in the samples from the riverbank forest than from the beach-ridge forest.