Structure of sensilla on maxillary and labial palps in caddisflies of the genus Rhyacophila Pictet, 1834 (Trichoptera: Rhyacophilidae)

: A comparative study of the structure and localization of sensilla on the palps of caddisflies from the genus Rhyacophila , the family Rhyacophilidae, was carried out for the first time. The structure of maxillary and labial palps in 15 species of the genus Rhyacophila was studied by scanning electron microscopy. Seven types and two subtypes of sensilla were found on these head appendages: pointed long trichoid sensilla, blunt chaetoid (gustatory) sensilla (two subtypes), campaniform sensilla, thick basiconic sensilla, petaloid sensilla, leaf-like pseudoplacoid and mushroom-like pseudoplacoid sensilla. The size of chaetoid and pointed trichoid sensilla on palp segments decreases towards the palp apex. Pseudoplacoid sensilla, as a rule, are found only on the terminal segments of the labial and maxillary palps, and in some species they completely disappear. Terminal segments of both pairs of palps have sensory fields formed by aggregations of petaloid sensilla. Apical sensory complexes are localized at the apical end of the maxillary and labial palps. At the top of these sensory areas there is a thick basiconic sensilla, on the lateral surface of the sensory complex there are rudimentary basiconic sensilla. The structure and localization of palpal sensilla, apical sensory complexes, and sensory zones with petaloid sensilla can be used for taxonomy purposes