THE INFLUENCE OF LARVAL SIZE, TEMPERATURE, AND COMPONENTS OF THE FUNCTIONAL-RESPONSE TO PREY DENSITY ON GROWTH-RATES OF THE DRAGONFLIES LESTES DISJUNCTUS AND COENAGRION RESOLUTUM (INSECTA, ODONATA)

Larval growth of Lestes disjunctus was completed in 70 d in the field, whereas in Coenagrion resolutum it took 10-22 months. This was not si mply the result of occupying warmer microhabitats, because L. disjunct us larvae grew faster than C. resolutum at all constant temperatures b etween 10 and 25 degrees C in the laboratory. Multiple regression anal ysis showed that growth rates of both species were positively related to temperature and negatively related to larval size and to the square of temperature. The latter term is necessary to describe the decrease in growth rate at high temperatures. The equation predicted that the growth rate of L. disjunctus reached a maximum at 28.8 degrees C, wher eas that of C. resolutum decreased above 22.4 degrees C. Small and med ium-sized larvae of L. disjunctus ate more prey (Daphnia magna) in 15 min than C. resolutum at all prey densities. In 15-min experiments the attack coefficient for small L. disjunctus larvae was significantly l arger than for small C. resolutum larvae and handling time for medium larvae was shorter. Other comparisons had large associated sampling er rors, but the trends were the same. These differences may be associate d with the relatively longer labia of L. disjunctus and its ability to change hunting methods from ambush to active search.