Oriental blue fly (Chrysomya megacephala)
Chrysomya megacephala, more commonly known as the oriental latrine fly or oriental blue fly, is a member of the family Calliphoridae (blowflies). It is a warm-weather fly with a greenish-blue metallic box-like body. The fly infests corpses soon after death, making it important to forensic science. This fly is implicated in some public health issues; it can cause accidental myiasis, and also infects fish and livestock.
Chrysomya megacephala has a wide geographical distribution. It is most common in the Oriental and Australasian realms. It is also found in Japan and the Palearctic realm. The range of C. megacephala has grown since the 1970s, with the species expanding into New Zealand and Africa, along with South, Central, and North America. C. megacephala entered the United States through harbors and airports. The fly has been found in California, as well as Texas, Louisiana, and Hawaii. C. megacephala exists in two forms, the normal and the derived. Tropical forests on the Pacific Islands, such as Samoa, are home to the normal form; the normal is considered to be the plesiomorphic form of C. megacephala. The derived form is thought to have emerged from Papua New Guinea and is said to be synanthropic, or ecologically associated with humans.
Chrysomya megacephala are known to be the source of accidental (secondary) myiasis in humans, where the flies do not pierce the skin but invade an open wound. The first record of human myiasis caused by C. megacephala and C. rufifacies was in Thailand, where a 53-year-old man had a tumor lesion where the larvae accumulated. Most recorded myiasis cases, however, do not involve the fly. C. megacephala is a carrier of pathogens, such as bacteria, protozoan cysts, and helminth eggs, to human food, because it lays its eggs on human feces, and will land on human food soon after.
The flies also cause a huge economic problem in Asia, Africa, and the Pacific. In these areas sun-drying is the major method of preserving fish, as ice is typically unaffordable. However, blowfly larvae tend to infect these sun-dried fish when the weather is warm and humid. In an experiment, 95% of the infecting flies were found to be C. megacephala. The flies can be controlled by using an odor that the flies are attracted to trap them. Insecticides are also used, although this results in the development of resistance.