The green blowflies belonging to the genus Chrysomya are a conspicious element of the fauna of markets and latrines in tropical Africa and Asia. At present three of the four species of Chrysomya introduced into the New World - C.putoria, C.megacephala and C.albiceps - have been found in Brazil.
Chrysomya putoria has anterior spiracles and lower squamma white. Single propleural (prostigmatic) bristle present. Body metallic dark blue and green, with a characteristic pattern; abdominal bands occupying approximately one-third of length of segments. The sanitary problems created to humans and animals by these flies are attaining increasing importance with the contemporary trend towards suburban living, with homes ans schools tending to a closer physical proximity to such fly-breedind foci created around stockwards, abbatoirs and city dumps.
Four species of Chrysomya have become established in the Neotropical region, where the dispersal rates have been estimated at 1.8 to 3.2 km/day. Their introduction has led to the suppression of the indigenous Cochliomyia macellaria. Chhrysomya putoria breed in wet faecal material and are commonly found breeding in latrines.
Chrysomya megacephala, an Old World calliphorid of considerable public health importance, was first discovered in Brazil in 1977 and is now widely distributed in Latin America. The fly has anterior spiracles and lower squammae brown; color greenish blue with purple reflections; posterior margin of second and third abdominal segments black.
Eyes of male with the upper facets strongly enlarged and sharply demarcated from the small ones in the lower third. The eusynanthropic form of C.megacephala is among the most dangerous dipteran vectors of enteric bacteria, protozoans, and helminths. The adults are attracted to a wide variety of human food, human and livestock feces, and carrion, and dense populations develop in urban and suburban areas.
Chrysomya megacephala is commonly called the oriental latrine fly because of its habit of breeding in faeces as well on carrion and other decomposing organic matter. It may occur in large numbers around latrines and may also become a nuisance in slaughter-houses, confined animal facilities, open-air meat and fish markets.
Filth flies are commonest in commercial egg-production cage-layered houses; less in breeder houses and least in broiler houses.These flies are fairly abundant in poultry houses where it breeds in accumulate manure.