Trichomycetes (Zygomycota) are a cosmopolitan class of filamentous fungi that are reported to live as obligate commensals in the guts of various arthropods, particularly aquatic insects. Most of our knowledge about trichomycetes is taxonomic or host-symbiont associations. Relatively little is know about their development, particular across different hosts. Development of the trichomycete Smittium culisetae was examined in three dipteran families and under different temperature regimes. Hosts used were Chironomidae, Culicidae, and Simuliidae. Size and measurements of trichomycete spores, germinal cells, collars and holdfasts are critical for species designations in trichomycetes. Hence a morphometric analyses of trichomycetes was compared among different dipteran host to determine if morphological features remain constant among hosts.