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The nematode-trapping fungus Arthrobotrys conoides grows as typical vegetative hyphae on laboratory media containing glucose or starch as sole carbon source. However, in the presence of nematodes, "nemin", and several of the aliphatic amino acids (such as valine), this predacious fungus forms traps which are composed of sticky loops. The present studies show that, when A. conoides is grown on a semisynthetic medium in which various carbohydrates are substituted for glucose as the carbon source available for growth, the nature of the carbohydrate exerts a major effect on the induction of trap formation.

In vitro growth studies showed that Arthrobotrys oligospora Fresenius, A. conoides Drechsler, A. musiformis Drechsler, and A. robusta Duddington are characterized by a fast, inherent growth rate relative to A. dactyloides Drechsler, Dactylella gephyropaga Drechsler, and Dactylaria brochopaga Drechsler, which grew slowly on all media tested. Arthrobotrys superba Corda, Dactylella ellipsospora Grove, and D. asthenopaga Drechsler were found to be intermediate in this respect. There was little correlation between the maximum rate of increase in colony diameter of the 10 species of nematophagous Hyphomycetes and their ecological requirements for such growth. The fast-growing species appeared to prefer media with a pH range of 5.0–6.0 and the slow-growing fungi a pH of about 4.0. No consistent similarity in environmental requirements was found among species of fungi belonging to the same genus or between those possessing the same kind of nematode-trapping organ. Lima bean agar of pH 5.0 was a satisfactory culture medium and incubation at 25 °C in continuous or intermittent light resulted in larger colonies than incubation in darkness.