Fine structure of Chrysomya nigripes (Diptera: Calliphoridae), a fly species of medical importance

The fine structure of Chrysomya nigripes Aubertin, a blow fly species of medical importance, is presented using scanning electron microscopy (SEM) to contribute information on the morphology of the adult of this fly species. The surface of the dome-shaped ommatidia exhibits a microscopic granulose appearance. The palpus is equipped with small sensilla basiconica and sensilla chaetica, which provide sensory reception for detecting environmental information. At the apex of the mouthparts, the labellum is endowed with large numbers of sensilla trichodea and basiconic-like sensilla of variable length. The anterior (mesothoracic) spiracle is elliptical in shape and covered with extensively ramified setae except for a small dorsal aperture. The posterior (metathoracic) spiracle is shaped like a rounded isosceles triangle and covered by two valves of unequal size. The larger valve covers the upper approximate to 2/3 of the spiracular opening, whereas the smaller valve covers the lower approximate to 1/3 of the opening. Extensively ramified setae line and cover the valves over the entire spiracle. SEM analyses of the haltere knob and the prosternal organs, located adjacent to the cervical sclerites, revealed a striking resemblance of the morphological features of their sensilla. Each sensillum emanates from a cuticular ring, is approximate to 12-15 mu m in length, has a smooth surface, and terminates in a sharp tip. Various types of sensilla were associated with the ovipositor including sensilla trichodea, sensilla basiconica, sensilla placodea and probably sensilla styloconica. The possible function of sensilla distributed in particular regions of the fly integument is discussed.