GROWTH AND SURVIVORSHIP DIFFERENCES IN EUROSTA (DIPTERA, TEPHRITIDAE) GALLING SYMPATRIC HOST PLANTS

Life history characteristics of the goldenrod gallmaker, Eurosta solidaginis Fitch (Diptera: Tephritidae), were compared between individuals using separate host species. Infestation rate, gall size, gallmaker larval weight, gallmaker mortality, and parasitoid/predator attack frequencies were examined. Galls from Solidago altissima L. (Compositae) averaged 10% less in diameter than those of S. Gigantea Ait. Discordantly, the larval weights of the S. Altissima larvae were 26% greater. Gallmaker mortality was approximately equal, although the underlying causes differed. Some of these differences can be explained by difference in gall size. The S. Altissima galls, with their smaller mean size, were more vulnerable to attack by the parasitoid wasp, Eurytoma gigantea Walsh (Hymenoptera: Eurytomidae). On the other hand, S. Gigantea galls, with their greater mean size, were more vulnerable to attack by birds. Early larval death of the gallmaker was greater on S. Gigantea. Although survivorship did not differ on the two host plants, the larger size of larval from S. Altissima would suggest that females emerging from this host would have greater fecundity. Although S. Altissima appears to be the better host, S. Gigantea was more heavily infested. The seemingly maladaptive lack of correlation between infestation and performance could be explained if the insects from the two plant species represent two host races. © 1990 Entomological Society of America.