Africa's tsetse folds its wings like stacked blades
Tsetse—genus Glossina, in their own family—are large biting flies across much of tropical Africa and parts of the Arabian Peninsula. Twenty-three living species are known; fossils turn up in Paleogene rocks of the United States and Germany. At rest they stack one wing atop the other.
Two field marks separate tsetse from lookalike big flies: at rest the wings fold completely over the abdomen, one lying squarely on the other, and a long proboscis juts straight forward from a distinct bulb under the head. Adults measure roughly 0.5 to 1.5 cm, with widely separated eyes, odd antennae, a bulky thorax and a short, broad abdomen. They are also tough; a swat that flattens a housefly barely troubles one.
Both sexes live entirely on vertebrate blood, and that diet shapes a strange reproductive strategy. A female fertilises a single egg at a time and keeps it in her uterus, feeding the growing larva a milky secretion from a modified gland, an arrangement called adenotrophic viviparity. The larva leaves her only at its third instar, crawls into soil within hours, and hardens into a puparium under 1 cm long. Everything it needs until it emerges as an adult about 35 days later comes from its mother, even though the offspring can outweigh her. Her crop, meanwhile, can swell to hold a blood meal equal to her own weight.
Because they carry trypanosomes, the parasites behind human and animal trypanosomiasis, tsetse carry heavy public-health and economic costs across sub-Saharan Africa. That, plus their size and the ease of rearing them in laboratories, makes them unusually well studied. The genome of Glossina morsitans was sequenced in 2014, and the flies host at least three bacterial partners, led by Wigglesworthia. Pigs and their relatives are the chief hosts, whereas waterbuck give off odours that repel the flies, now being tested to protect cattle.
Twenty-three living species are known from Africa and the Arabian Peninsula, all in Glossina, usually treated as the only genus of Glossinidae; counting subspecies, some schemes recognise up to 34. They fall into savannah, forest and riverine or lake-shore groups. Fossils from Paleogene rocks in the United States and Germany show the lineage once ranged far wider. The name comes from Sotho, and a wartime British antisubmarine aircraft, the Tsetse Mosquito, helped spread it in English.
Source: Tsetse fly
