Structure and distribution of sensilla on the mouthpart palps in the caddisfl ies of the family Hydropsychidae (Trichoptera)

Abstract

A comparative morphological study of the structure and distribution of sensilla on the maxillary and labial palps in representatives of the family Hydropsychidae was performed. Morphology of palpal sensilla was studied in 17 species from 12 genera by scanning electron microscopy. Four types of sensilla were found on the palps of the studied species: long trichoid sensilla, chaetoid sensilla, campaniform sensilla, and petaloid sensilla; basiconic and pseudoplacoid sensilla were not found on palps. All studied species lack apical sensory complexes at the tips of both pairs of palps, where only long chaetoid sensilla are present. Petaloid sensilla form sensory elds on the 4th (in Arctopsychinae) or on the 3rd and 4th segments (in Diplectroninae, Hydropsychinae, Macronematinae) of the maxillary palps. These sensilla are never present on the labial palps. Sensory elds include from 5-10 sensilla in Hydropsychinae to 40 in Arctopsychinae.