This question was put to me this weekend as hundreds, if not thousands, of little black winged insects (approx. 3mm long) settled on the white walls of our house and are doing so again today. These are the parthenogenetic, or agamic, generation of a gall wasp (Neuroterus quercusbaccarum) that lives on oak trees (Quercus). The warm weather has encouraged them to hatch and swarm. This generation will lay its eggs on oak catkins, producing little round galls that each house a single larva. Later in the year this larva will turn into the sexual generation (male and female) of the wasp which lays its eggs on oak leaves and produces spangle galls. These galls fall off in the autumn and shelter the agamic generation through the winter prior to hatching the following spring. These gall wasps do not bite or sting.