Trichogrammatidae are almost entirely parasitoids of insect eggs. They include some of the smallest insects known, and possess many extreme modifications associated with size reduction. The family is named after the characteristic rows of setae on the fore wing. Trichogrammatids are frequently released in large numbers to control insect pests, in part because egg parasitism ensures that attacked pests will not cause damage as larvae.
Megaphragma is the smallest known trichogrammatid, being smaller than many single-celled organisms. Research conducted by Alexey Polilov indicates that nervous system in Megaphragma is made up almost entirely of anucleate cells! Yet, they can fly and search for hosts capably.
Most trichogrammatids are considerably smaller than adults of their host species. Multiple species are known to use a behavior known as phoresy, hitching a ride on another insect and leaving when near a host egg.
Hydrophylita emporos, phoretic on a damselfly
All photographs were available for re-use on Wikimedia Commons:
Trichogramma dendrolimi was photographed by Victor Fursov.
Megaphragma mymaripenne was photographed by Alexey Polilov.
Hydrophylita emporos was photographed by Yuan Tung Shih et al.