Not all gall wasps (family Cynipidae) affect the leaves of their hosts—some instead affect the twigs. One example of such is Disholcaspis quercusglobulus (round bullet gall wasp), which forms round, detachable galls, singly or in small clusters, on the twigs of Quercus alba (white oak).
There are about a dozen other species in this genus, all of which seem to to have succeeded in eliminating the need for males (Weld 1959). All galls produce female wasps, which emerge from their galls during the fall and immediately lay eggs in twigs to begin the next year’s crop of females—no males needed. Ain’t evolution grand?!
Weld, D. 1959. Cynipid Galls of the Eastern United States. Privately printed in Ann Arbor, Michigan [pdf].
©️ Ted C. MacRae 2021