ONTOGENIC BEHAVIOR CHANGES IN LARVAE OF THE DAMSELFLY ISCHNURA-VERTICALIS (ODONATA, COENAGRIONIDAE)

Larvae of most animals go through large changes in size. Because chang e in size can lead to changes in ability to gain food and in predation risk, changes in behaviour are predicted to reflect this. Models cons ider change in amounts of the same behaviour, but different selective pressures on different larval sizes may also lead to qualitative diffe rences in behavioural repertoire. In the damselfly Ischnura verticalis we observed ontogenetic changes in behaviour under controlled laborat ory conditions. We found that frequency and duration of feeding behavi our and behaviour related to activity were increased in larger instars . Larger larvae also had higher transition probabilities to the behavi our abdomen wave, straight abdomen raise, and rotate + head out. We al so found that the behavioural repertoire of damselfly larvae changed w ith development: some behavioural patterns were performed almost exclu sively by smaller larvae (F - 4 to F - 7) while others were performed almost exclusively by larger larvae (F - 3 to F - 0).