Comparison of the fat allocation patterns in female pine sawflies (Hymenoptera : Diprionidae)

The allocation of fat resources to somatic and reproductive tissues was studied in females of five species of pine sawflies (Diprion pini (L.), Diprion similis (Htg.), Gilpinia frutetorum (F.), Gilpinia pallida (Klug), Neodiprion sertifer (Geoffroy); Hymenoptera, Diprionidae). The soma and eggs of newly emerged females were separated and then put in ether to extract and determine their fat content. The fat allocation patterns differed between species. The gregarious outbreak species D, pini and N. sertifer allocated most of the fat to their eggs, whereas the gregarious non-outbreak species, G. pallida, allocated most to its somatic tissues. No modification of these basic allocation patterns was observed with increasing total fat content. In contrast, the solitary non-outbreak species, D. similis and G. frutetorum, invested equal amounts of fat in soma and eggs, and the proportion allocated to the egg load decreased as total fat content increased. That is, they invested additional resources in somatic tissues. Apparently, outbreak species tend to allocate more fat to reproductive tissues than non-outbreak species.