Just 0.5 mm, these wasps are rather small for light microscopy..... This SEM picture of the egg parasitoid Trichogramma evanescens on an egg of the Large White butterfly was made with Marcel Giesbers at the Wageningen EM centre. The black and white image was colored thereafter in photoshop. Below also a focus stacking picture with a macro camera. This species can parasitize and completely develop within the eggs of Lepidopterans. Their brain is just 200 micrometers in size but still these wasps can show a complete behavioral repertoire, see this link
The egg parasitoid wasp Trichogramma evanescens lays her eggs inside the eggs of the large cabbage butterfly, Pieris brassicae. This wasps species is about 0.5 mm long