First stage maggots ofLixophaga diatraeae(Townsend) successfully entered 1st, 2nd, 3rd, 4th, early 5th, and late 5th stage larvae and untanned and tanned pupae of the sugarcane borer,Diatraea saccharalis(F.). Percentage parasite maggots completing development to the pupal stage was reduced in 1st and late 5th stage host larvae and untanned pupae. No maggots completed development in tanned pupae. Maggots readily entered host larvae in all stages, but their ability to seek out younger host larvae in artificial diet contained in 30-ml cups was reduced. Host larvae parasitized during the 1st to early 5th larval stage underwent additional molts during parasite maggot development, but did not pupate. The duration of the parasite maggot period (male and female) decreased with advance in host larval stage parasitized up to the 4th stadium, and this decrease was associated with decreasing duration of the parasite maggot prefunnel period. Parasite puparia (male and female) from older host larvae generally weighed more.