Redescription of 1st instar larva of Osmylus fulvicephalus (Scopoli, 1763) (Neuroptera, Osmylidae) based on naming system of sclerites

Osmylidae was an ancient family of Neuroptera, including more than 200 species, and usually live in forest or near water body. So that its larvae have been seldomly described. The taxonomic studies on the larvae of of Osmylidae, especially the type species Osmylus fulvicephalus (Scopoli, 1763), focused on the third instar larvae. The lower instar stages of this species lack sufficient description. Currently, the first instar larva of only two species, Stenosmylus tenuis (Walker, 1853) and Osmylus fulvicephalus (Scopoli, 1763), had been recorded and described, but the morphological description of Osmylus fulvicephalus was too simple to be distinguished with other species. In this study, the first instar larva of O. fulvicephalus was redescribed in detail and illustrated based on the naming system of sclerites. Based on this, it could be effectively distinguished from other species by the following characteristics: i) number of segments in the labial palpus; ii) the setae beard on the apex of antenna; iii) the number of transversal rows of the anal hooks.