Cynipidae - gall-forming wasps
This family of wasps contains more than 1,000 species which are found in temperate and subtropical regions. Most of them induce galls of various forms in their host plants or are inquilines. The galls are formed in all plant parts ranging from roots, over leaves and buds to flowers. Pupation takes place inside the gall and no cocoon is constructed.
In many species there are 2 generations per year with one of them reproducing parthenogenetically. The adults are typically small (1-3 mm long) and black or darkly coloured.
For details see the respective page in Wikipedia.
The following genera and individual species are currently entered under this family: