species may have greatly reduced stubby wings or lack wings altogether. They can be distinguished from other chalcidoids by the H-shaped pattern of sutures on the front of their heads.

The viscous effects of air on a wing increase at smaller sizes, so an insect 1mm or smaller moves through the air as a bumblebee would move through mineral oil. The smallest example of powered flight currently known to humans is that of miniature insects, with wing lengths typically no greater than 1 mm. Flight in this domain is characterized by Reynolds numbers