Morphology and ultrastructure of spiracles in phlebotomine sandfly larvae

The morphology and ultrastructure of the larval spiracle system of three ph lebotomine sandfly species, Phlebotomus perniciosus, P.perfiliewi and P.pap atasi, were examined by scanning (SEM) and transmission (TEM) electron micr oscopy and by confocal scanning laser microscopy (CSLM). During larval deve lopment, thoracic and abdominal spiracles show considerable modifications. In fourth instar larvae, the spiracles consist of a plate with a sclerotize d central portion and a peripheral circle of papillae. The latter is distin ctive in the larvae of P.papatasi, which are readily distinguished from the other species. Opening clefts across the papillae communicate with an inte rnal chamber that encircles an electrondense plug. Many cylindrical project ions cross the chamber, uniting the central plug with the larval body, form ing an air filter. Spiracular development in successive larval instars has both a taxonomic and adaptive value.