Inspection and evaluation of host plant by the butterfly Mechanitis lysimnia (Nymph., Ithomiinae) before laying eggs: a mechanism to reduce intraspecific competition.

Females of Mechanitis lysimnia (Lepidoptera: Nymphalidae) show a characteristic searching, inspecting and evaluating behavior on their Solanum host plants. The average egg-clutch size for this butterfly varied with the host species of Solanum. There was a positive relationship between the egg-clutch size of M. lysimnia and the number of leaves, indicating an adjustment between the reproductive effort of the insect and the amount of food available to its offspring. Field experiments showed that butterflies were able to recognize conspecific egg-clusters by visual cues and preferred to lay eggs on egg-free host plants. On large plants that received two or more egg-clusters, later clutches contained fewer eggs than the first one. The butterflies seem to evaluate the amount of food by inspecting the quantity of leaves and by checking for presence or absence of eggs and, possibly, caterpillars before deciding if and how many eggs to lay. These behavioral mechanisms should be important in reducing direct intraspecific competition for the five rare, small and ephemeral host plant species used by this insect.