Scanning electron microscopy studies of sensilla and other structures of the head of Polygenis (Polygenis) tripus (Siphonapera: Rhopalopsyllidae)

The external morphology of the head and appendages of adult Polygenis (Polygenis) tripus [Jordan, K., 1933. Descriptions of Siphonaptera. Nov. Zool. 39, 66–69] (Siphonaptera: Rhopalopsyllidae) was described based on scanning electron microscopy. Chaetal, trichoid and basiconic sensilla were encountered and their positions noted, comparisons being made between male and female specimens. Those of the basiconic type were particularly abundant on the frontal and occipital regions of the head and were surrounded by several pores, indicating the considerable sensory importance of these areas. Frontal tubercle was observed as a projection emerging from a depression in the frontal head region. The antennae of males were more developed, presenting greater number of sensilla on the scape and about 370 spatulate setae on the internal surface of the clava. Three large chemoreceptors, digitate sensilla ca. 11–13 μm were observed on the lateral surface of the antennal clava of both sexes between antennomeres 4–7. Females present a characteristic distribution of basiconic sensilla on the dorsal margin and median external surface of the clava. Trichoid sensilla were observed on all segments of the maxilary palps while basiconic sensilla were only recognized on the distal three segments.