FAT AND EGGS - AN ALTERNATIVE METHOD TO MEASURE THE TRADE-OFF BETWEENSURVIVAL AND REPRODUCTION IN INSECT PARASITOIDS

The cost of reproduction, a trade-off between reproduction and surviva l, is important in life history study. In parasitoids this trade-off i s studied by measuring number of offspring and longevity. Measuring lo ngevity, however, is a time consuming method and probably does not ref lect a realistic value for survival in the field. I present an alterna tive method, which uses fat content as a measure for survival. Using t he insect parasitoid Asobara tabida (Nees) (Hymenoptera), I show in tw o ways that fat content is strongly correlated to longevity. Firstly, strains with a higher fat content have a greater longevity. Secondly, fat reserves decrease linearly with age. The trade-off between reprodu ction and survival can be studied using this method. There is a negati ve correlation between the number of eggs in the ovarioles and the fat content of A. tabida females. This indicates that there is a cost of reproduction in A. tabida. The most important advantage of this method is that measuring fat content is a quick method. This method may also be applied to other insect species.