A relatively small, mainly black spider wasp with yellowish tinged wings, which have a variable amount of dark colour at the tips.

This pattern appears to be an example of Allen's rule and is seen in other New Zealand Pompilids but is less marked in E. insularis due to its greater extent of sexual dimorphism with the males always being more uniformly dark.

[1] E. insularis females hunt, usually in sunshine for retreat-making spiders in the concealed places where female spiders retreat to, such as rolled dead leaves; hollow plant stems; flax bushes; dead rolled fronds of tree-ferns; the abandoned cocoons of the bag-moth Liothula omnivora; deserted galleries of wood-boring beetles; and even the empty hatched galls of the moth Morova subfasciata in Muehlenbeckia australis and beneath loose bark on tree trunks.

[1] E. insularis was placed by Evans in the subgenus Epipompiloides due to the structure of the male's subgenital plate which is very similar to that of E.

[1] This latter species is from southern Australia but in 1972 Evans stated that the subgenera of the Australian and Papuan Epipompilus are of dubious validity.