Abstract:The distinctive thalli of trichomycetes can only be isolated from the larval stage of the host. There is a general lack of knowledge on the presence of trichomycetes in other developmental stages of their host. Two new primers, TR3F and TR4R, were designed based on SSU ribosomal DNA sequences from two Harpella species, one Harpellomyces species, four Smittium species and Aedes aegypti (host). These primers amplified DNA from species of the Harpellales but discriminated against other groups of organisms including other fungal phyla. The presence of Smittium species was detected in laboratory-infected pupae and adult flies of Aedes aegypti and in field-collected larvae of Culex pipiens by PCR using the new primers.