I described pupal chamber location, construction, and larval size relationships of the dobsonfly,Corydalus comutus, from 72 larvae collected in 1988 and 27 pupae in 1990. Larvae constructed pupal chambers beneath a variety of objects and debris (55% of which was man-made refuse). Anatomical measurements of pupae indicated sexual dimorphism; generally, males had significantly wider head capsules (P = 0.01) and longer mandibles (P = 0.01) than females. Significant correlations (P<0.05) were observed between larvae and pupae sizes and chamber sizes. Proper location and construction of pupal chambers can minimize the effects of adverse environmental factors.