Oak Rough Bulletgall Wasp

As in all Hymenoptera, sex-determination in Disholcaspis quercusmamma is governed by haplodiploidy: males develop from unfertilized eggs and are haploid, and females develop from fertilized eggs and are diploid. The life cycle of Disholcaspis quercusmamma alternates between an asexual (agamic) generation and a sexual generation, producing two different types of galls at different seasons of the year.

Asexual generation. The conspicuous bullet galls seen in summer and fall contain only female larvae. When mature, female adults emerge in late fall and reproduce parthenogenetically. The females are self-fertile and lay a single egg in a dormant leaf bud. These eggs along with the resulting wasp larvae stimulate the tree to produce small, inconspicuous leaf galls in the spring.

Sexual generation. Both male and female wasps develop inside the spring leaf galls and adults emerge in mid-to-late spring. The mated females fly or crawl to newly elongated twigs where they insert their eggs through the phloem to be in contact with the cambium, where undifferentiated (meristematic) cells are stimulated to grow the fall bullet galls.