The above gall is caused by the activity of Cynips maculipennis, a member of the Cynipidae family and inthe order hymenoptera. The body of C. maculipennis is approximately 2mm long and is black in color. The two segemted abdomen is visible dorsally, and the other segments extend beneath the body. The venation on the wing is very reduced.
Member of the Cynipiddae, or gall wasp family are among the most difficult insects to identify due to small size and requirement of host data and life history. The gall formed as a result of the wasp is typically a better indicator of the identity of the wasp than finding and evaluating the insect.
The gall is formed when the wasps insert eggs into tissue of buds, stems or roots on oak tree. The secrections of the larvae cause the plant to have abnormal cell growth.
Arndt and Jacques