BITING FLIES IN BRITISH EAST AFRICA 89 
are characterised by the possession of a spur at the tip of the 
tibia of the hind leg. 
Pangonia has now been subdivided into several genera, 
but for our purpose it will be sufficient to treat it as one. 
The flies of this genus are usually rather large insects, some 
of them, especially some of the smaller species, being rather 
like a bee in general appearance. They are easily distinguished 
by their long (sometimes very long) proboscis sticking out 
horizontally in front of the head. The wings are dark or clear 
but not mottled or spotted and are carried somewhat extended 
even when the fly is at rest. The abdomen is not spotted, as 
in a few species of Tabanus and many of PLaemalopota , but 
frequently bears a number of transverse bands of different 
colours. 
The genus Chrysops comprises rather small, often brightly 
coloured flies. Their proboscis is directed downwards as in 
PLaemalopota , and their wings, though not spotted, generally 
have one or more broad dark bands on them, the tip being 
usually also dark. Their wings are carried as in Tabanus 
not as in PLaemalopota , i.e. not tectiform. Their eyes are very 
beautiful, being in most species purple with zigzags of golden 
green. Indeed the eyes of most Tabanidae are well worth 
examination, and as they lose their colour after death careful 
note of the colour and markings should be made as soon as 
possible after capture. Two other very important genera of 
biting flies, Glossina and Stomoxys , belong to an entirely different 
family of Diptera , the Muscidae , to which the house-flies and 
bluebottles also belong. They differ completely from the 
above described genera in the form of their antennae. These 
are much less conspicuous than in any of the above, and the 
most prominent part of the antennae is somewhat featherlike 
instead of being single and rather stiff as in Tabanus, &c. 
The genus Glossina comprises the well-known Tsetse flies. 
These are small or medium-sized flies, varying from a trifle 
larger than a house-fly to about twice that size. They are of 
various shades of brown or black without very distinct markings. 
They are characterised by the fact that when at rest their 
wings overlap like the blades of a pair of scissors as well as by 
the possession of a biting proboscis, the protecting sheath at 
