816 Marvels of the Universe 
We must now, with the help of the accompanying illustrations, all of which have been photo- 
graphed from actual specimens, endeavour to give the reader some idea of the outward appearance, 
habits, and life-history of Tsetse-flies, and also indicate where they are found. Before doing so, 
however, it is necessary to point out that it is altogether wrong and misleading to say ‘“‘ the Tsetse- 
fly ” (just as we speak of “ the” lion or “ the”’ tiger), as though there were but a single species or 
kind in existence. Naturalists to-day are acquainted with no fewer than fifteen existing species 
or kinds of Tsetse-flies, all 
| lj agreeing with each other in 
ss their essential characteristics, 
y but differing in minor details 
of structure, markings, and 
habits, and, what is more im- 
portant, also it may be differing 
in their disease-carrying pro- 
perties. 
Although at an earlier stage 
of the earth’s history at least 
two species of Tsetse-flies are 
known to have existed in 
North America, at the present 
day these insects—with the 
exception of one kind, the 
range of which extends into the 
south-west corner of Arabia— 
are found only in Africa, where 
they are practically restricted 
to the Tropical portion of the 
continent. It must not be 
supposed, however, that Tsetse- 
flies occur everywhere within 
the area mentioned; on the 
contrary they usually show a 
peculiar limitation to particular 
tracts, which are often of very 
limited extent, and are known 
as “ fly-areas,”’ “ fly-belts,’’ or, 
ei ) a pears aaa in Africa, south of the great 
THE CLAWS OF THE ALLOSAUR. lakes, “ the fly.” Some kinds 
That such a claw could do enormous damage goes without saying. The longest of Tsetse are met with only 
digit measures over twelve inches. The fore-limb, however, was short, and could not close to water : others may be 
possibly have been used for walking, 
encountered at a considerable 
distance from any river, stream, or lake, even on low hills and up to an altitude of some five 
thousand five hundred feet. Open grass plains, however, are always free from Tsetse-flies, since 
cover in the shape of more or less thick bush or forest, shady trees, or reeds, is essential to their 
existence. 
A good idea of the general appearance of Tsetse-flies, as seen when at rest upon a twig or with the 
wings extended in the attitude of flight, may be gained from our illustrations, which represent the 
two kinds of Tsetse known to convey Sleeping Sickness from man to man. While differing, as 
already mentioned, in certain respects according to the species, the insects with which we are 
