Larval morphology of the avian parasitic genus Passeromyia: playing hide and seek with a parastomal bar.

ABSTRACT

The enigmatic larvae of the Old World genus Passeromyia Rodhain & Villeneuve, 1915 (Diptera Muscidae) inhabit the nests of birds as saprophages or as haematophagous agents of myiasis among nestlings. Using light microscopy, confocal laser scanning microscopy and scanning electron microscopy, we provide the first morphological descriptions of the first, second and third instar of P. longicornis (Macquart, 1851) (Diptera Muscidae), the first and third instar of P. indecora (Walker, 1858) (Diptera Muscidae), and we revise the larval morphology of P. heterochaeta (Villenueve, 1915) (Diptera Muscidae) and P. steini Pont, 1970 (Diptera Muscidae). We provide a key to the third instar of examined species (excluding P. steini and P. veitchi Bezzi, 1928 (Diptera Muscidae)). Examination of the cephaloskeleton revealed paired rod-like sclerites, named 'rami', between the lateral arms of the intermediate sclerite in the second and third instar larva. We reveal parastomal bars fused apically with the intermediate sclerite, the absence of which has so far been considered as apomorphic for second and third instar muscid larvae. Examination of additional material suggests that modified parastomal bars are not exclusive features of Passeromyia but occur widespread in the Muscidae, and rami may occur widespread in the Cyclorrhapha.