A parasitic fungus to moth larvae and pupae, Paecilomyces tenuipes, was isolated and cultured on liquid and agar media. Fruit bodies, or synnemata, with characteristics of P. tenuipes were successfully formed on the agar medium. When pupae of wax moth, Galleria mellonella, were incubated with the conidia, all the pupae were infected and the synnemata were formed out of them. Almost the entire length of 18S rDNA of P. tenuipes was amplified by PCR and directly sequenced. Molecular phylogenetic analysis demonstrated that it belongs to the subphylum Ascomycotina, the class Pyrenomycetes, the order Clavicipitales. This result is compatible with the suggestions that P. tenuipes may be the anamorph of an entomogenous fungus of the genus Cordyceps.