Consistent individual differences in the foraging behaviour of forest tent caterpillars (Malacosoma disstria)

Outbreaking insects are often considered identical units despite recent work in behavioural ecology that shows repeatable differences can exist between individuals and can have important implications for individual fitness and population processes. However, although entomologists have neglected the hypothesis that differences between individuals can play an important role in the ecology of a species, it is not new. Wellington (1957. Can. J. Zool. 35: 293-323) suggested that consistent individual differences in behaviour may play a role in the population dynamics of Malacosoma (Hubner, 1820) species (Lepidoptera: Lasiocampidae). We used a novel approach to determine if individual larval Malacosoma disstria Hubner, 1820 exhibit distinct and repeatable behavioural traits. Second-instar caterpillars were placed on individual arenas for I h on 4 consecutive days, and the proportion of time spent walking, searching, quiescent, and eating was documented. Active and sluggish behavioural types were distinguished and stable differences in individual activity were observed. Activity was positively correlated with growth during the 4 days of the experiment, but no significant relationship was detected between behaviour during the experiment and overall larval performance in the laboratory setting. These findings demonstrate consistent variation in the foraging behaviour of forest tent caterpillars and lay the basis for further investigatison of its role in colony function and population dynamics.