Parasitoids use a variety of cues to assess the quality of their hosts. After examination, the hosts may be used for oviposition and as a source of food, or may be rejected. Host acceptance, host feeding, and oviposition preference by Spalangia endius, Pachycrepoideus vindemiae, Nasonia vitripennis, and species of Diapriidae on five species of blowflies were observed in the laboratory. We offered similar-aged pupal hosts: Chrysomya megacephala, C. albiceps, C. putoria, Cochliomyia macellaria, and Lucilia sericata in no-choice and multiple-choice experiments. Logistic regression and MANOVA were applied to analyze the results in the no-choice and multiple-choice experiments, respectively. The results showed that the use of hosts differed among the parasitoid species. Spalangia endius and P. vindemiae showed no oviposition preference among the hosts. Diapriids and N. vitripennis preferentially attacked C. megacephala. The pupal host of C. macellaria was always avoided by diapriids. In the choice experiments, the clutch size of gregarious parasitoids was observed. The host C. megacephala allowed the highest number of clutches for diapriids. Clutch size in N. vitripennis did not differ among hosts. The feeding behavior on the host also changed in response to availability of hosts. In choice experiments, diapriids, N. vitripenis and S. endius used the same host species to lay eggs and to feed, whereas P. vindemiae did not use the same host species for oviposition and feeding.