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198 bara, Hydrochcerus capybara, a large water mammal of South America belonging to the family Caviidae. Nothing positive is known about its transmitting agent; Stomoxys calcitrans and Stomoxys nebulosa have been blamed. T. equinum causes in horses a deadly disease known as "mal de caderas " in Brazil, Argentina, and Central South America.

T. theileri.—Laveran (1902) reports the discovery by Theiler in the Transvaal of a trypanosome twice the size of any of the foregoing, and peculiar to cattle; so far, other domestic animals have been found to be immune. Theiler regarded it as producing an acute pernicious anaemia without poikilocytosis, and with only slight accompanying fever. He considers "that there exists a natural immunity in cattle against this trypanosome." Theiler believed that the transmitter of this parasite was a spider-fly, Hippobosca rufipes. Another species, H. maculata, recently imported with cavalry from India, is believed to be aiding in spreading the parasite. The disease is known as "galziekte," or bile-sickness, in the Transvaal. More recently, however, Theiler has altered his views, and now believes the disease to be due to a small piroplasm, Anaplasma marginale.

The Glossinae are sombre-coloured, narrow-bodied flies from about 8 to 12 mm. long, with a thick proboscis (i.e. proboscis enclosed by the palpi) projecting horizontally in front of the head. Their wings are large, of a brownish hue, and present a characteristic venation (Plate IV.) somewhat resembling that of the warble-fly (Hypoderma). The most striking peculiarity in the wing is the course of the fourth longitudinal vein, which about the middle of the wing bends abruptly upwards to meet the short and very oblique anterior transverse vein; here, describing a right angle, it runs obliquely downwards to meet the posterior transverse vein, and then turns upwards to reach the margin of the wing well in front of the apex. When the tse-tse is at rest its wings overlap on the back, crossing each other like the blades of a pair of scissors. This resting attitude of the wings, besides giving the fly a peculiar elongated appearance, renders it readily distinguishable from those other blood-sucking diptera with which it might be confounded, such as the stinging-fly (Stomoxys} and the cleg (Haematopota). Stomoxys is smaller in size, has short palpi not protecting the proboscis, and its wings diverge at an angle when resting. Haematopota presents prominent antennae and its wings are tectiform, i.e. they meet together at the base like the roof of a house and diverge slightly at the tips. In some species of Glossina the abdomen is crossed by sharply defined dark brown stripes, interrupted at the middle line. In the males, beneath the end of the abdomen, the external genitalia form a conspicuous knob-like protuberance which renders the sexes easily distinguishable.