Laboulbeniomycetes is a unique class of fungi within the phylum Ascomycota, known for their obligate ectoparasitic lifestyle on insects and other arthropods. Unlike most fungi, members of this class do not form typical mycelial networks; instead, they grow as tiny, specialized thalli directly on the external surface of their hosts. Laboulbeniomycetes exhibit a high degree of host specificity, often infecting only particular species or even certain body parts of the host. They reproduce through ascospores, which are transmitted during host contact, mating, or social interactions. These fungi are of interest in studies of host-parasite coevolution, biodiversity, and the ecological impact of parasitism on insect populations.