. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. Fig. 228. position. Tsetse fly in resting X 4. (After Austen.) General Form. — The tsetse flies (Fig. 228) are elongate, dark brown or yellowish brown flies, some species no larger than an ordinary housefly, others larger than blowflies. They are usually in- cluded as an aberrant group of the housefly family, Muscidse, but from other members of the family they differ in a number of striking ways, especially in the manner of repro- duction, and in form of the larva. They constitute the genus Glossina whi
. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. Fig. 228. position. Tsetse fly in resting X 4. (After Austen.) General Form. — The tsetse flies (Fig. 228) are elongate, dark brown or yellowish brown flies, some species no larger than an ordinary housefly, others larger than blowflies. They are usually in- cluded as an aberrant group of the housefly family, Muscidse, but from other members of the family they differ in a number of striking ways, especially in the manner of repro- duction, and in form of the larva. They constitute the genus Glossina which contains 15 species and has no very close allies; some species are of very wide distribution, while others are local or very rare. Tsetses can most easily be distinguished from other flies by their position when at rest (Fig. 228); their wings are folded flat, one directly over the other, straight down the back, like the blades of a pair of scissors, while the proboscis projects horizontally in front of the head. Beyond these characteristics there is noth- ing strikingly distinctive about a tsetse fly, and it is therefore difficult for anyone who is not thoroughly familiar with it to identify it on the wing. The darting manner of flight and buzzing sound are said to be quite diagnostic when one is once familiar with them. When the flies are caught and examined, however, there are a number of good identification marks. Most charac- teristic, perhaps, is the arrangement of the mouthparts and antennae (Fig. 229). The proboscis consists of a bulblike base which is continued as a slender shaft, com- posed of a grooved lower lip with two needle-hke puncturing organs within it, one of which, the hypopharynx, contains a deHcate tube for carrying the salivary juices. The proboscis proper is ensheathed in the maxillary palpi which are so grooved as to conceal entirely the. -r label. Fig. 229. Head and mouthparts of tsetse fly; ant., antenna; ep., epi- pharynx; hyp., hypo- pharynx; p
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