Copyright © 1983 Published by Elsevier Ltd.
Received 1 June 1982;
At their winter aggregation sites, convergent ladybird beetles, Hippodamia convergens (Coccinellidae), become active during snow-free days but form dense clusters in protected microhabitats at night. This daily dispersal and nightly reformation of clusters is correlated with two temperature-sensitive behaviours. Laboratory experiments demonstrated that ladybird beetles become photopositive as the temperature in a controlled environment room decreases from 20 C to 7 C, but they revert to a photonegative response as the temperature falls below 5 C. Also, ladybird beetles tend to form clusters as the temperature falls from 35 C to about 15 C. An attractant pheromone assists in cluster formation. Possible selective advantages of cluster formation by ladybird beetles are discussed.