Effect of Body Size and Feeding on Fecundity in the Damselfly Ischnura verticalis (Odonata: Coenagrionidae)

Abstract

We looked for relationships between number of eggs and the independent factors of food availability and body size in lab-reared females of the damselfly Ischnura verticalis. Multiple regression analysis revealed a strong positive relationship between number of eggs in the abdomen and both short term and long term food intake. There was no relationship between body size (wing length or head width) al maturity and number of eggs in the abdomen. Larval diet during the final instar affected development rate and adult size but not fecundity. Food consumed after emergence was negatively correlated with time to sexual maturity. Significantly more animals given low food diets died before maturity. Field data of gut weights suggest that animals in the field frequently have empty guts and we infer that food availability may be an important determinant of realized fecundity. Failure to find food on any one day will have consequences, not only for clutches laid the next day, but also for subsequent clutches, and finally for probability of surviving to the next day.