We compare the growth and development of two related solitary endoparasitoids (Braconidae, Microgastinae) in different instars (second and third) of the diamondback moth Plutella xylostella. Cotesia vestalis is a well-studied parasitoid whose larvae feed primarily on host hemolymph and fat body whereas Dolichogenidea sicaria is a parasitoid whose larvae consume the entire host caterpillar before pupation. Little is known about the biology of D. sicaria including its association with P. xylostella. When developing in L2 and L3 host instars, survival of both parasitoids to adult was similar. However, development time was longer in D. sicaria than in C. vestalis but the adult wasps were also larger. Both species were protandrous and exhibit sexual size dimorphism, where females were the larger sex. Our results suggest that D. sicaria is a promising new biological control agent of P. xylostella, augmenting better studied parasitoids such as C. vestalis.