dark marks. While certain species of Culicoides, such as C. austeni and C. grahamii have been hypothesized to play a larger role than other species in the transmission of M. perstans, very few studies have attempted to identify the species of vectors of M. perstans in endemic areas. This issue is further complicated because the taxonomy of tropical Culicoides species is still uncertain. Biting midges progress from egg, to larva, pupa, and finally the adult stage. The complete cycle takes 2–6 wk, and is dependent on environmental conditions. The females usually bite around dawn and dusk, although often at other times. Eggs are laid 3–4 d after the blood meal, and about 70-180 eggs are laid each time. Moisture is essential for the vector, and the development of its eggs and larvae. Adults survive for a few weeks, and their flight range is limited to a few hundred meters from their larval habitats. Morphology Adults are white and thread-like, and have been found to be cylindrical in shape. Males are 35–56 mm long and 45–60 μm wide. Females are bigger, 70–80 mm long and 80–120 μm wide. The tail is half a coil in females and a full coil in males. Adult worms are rarely seen, but sometimes can be recovered from a laparotomy or autopsy. Microfilariae of M. perstans are unsheathed, have blunt tails, and their nuclei extend to the end of the tail. The microfilariae have a length of 200 μm, and a width of 4.5 μm. They have the ability to elongate and contract, so they can vary in measurement and form. They are smaller than those of Loa loa, which have tapered tails and are frequently coiled. The microfilariae of M. perstans are smaller than those of W. bancrofti and the caudal end is blunt with a terminal nucleus. Lifecycle During a blood meal, an infected midge (Culicoides grahami and C. austeni) introduces third-stage (L3) filarial larvae onto the skin of the human host, where they penetrate into the bite wound. Body heat likely activates the larvas and prompts them to leave the vector and actively penetrate the skin. The third-stage larvae develop into adults that live in body cavities, most commonly the pleural and peritoneal cavities. They also can live in mesentery, perirenal spaces, retroperitoneal spaces, or the pericardium, and mature into adults. Adults in the body cavities mate and produce unsheathed and subperiodic microfilariae