338 THE LIVING ANIMALS OF THE WORLD 
animals ; or, when that fails them, they may 
attack caterpillars, or other small soft-bodied 
creatures. Though not very particular about 
their food, different species are more or less 
attached to different animals ; and while in 
Europe the most troublesome species is the one 
considered to be most particularly attached to 
man, the species most troublesome in North 
America is known in Europe as the Dog-FLEA. 
They are all very similar in habits and appear- 
ance. Fleas are not only annoying, but, in con- 
junction with rats, are believed to be among the 
principal agents inthespread of theplague. There 
is another insect called the JiGGER, or Sand-FLEA, 
common in most of the warmer parts of America, 
and which has more recently been introduced 
into Africa. The female burrows into the feet of men or animals, where her body swells up 
with eggs to the size of a pea; and serious and sometimes fatal ulcers are the ordinary result, 
unless the insect is carefully extracted at an early stage of the attack. 
Photo by IV.P.Dando, F.Z.S. 
BEE-FLY 
Similar to the jly luhich destroys the locust eggs in Cyprus 
Uses of Flies 
It must not be supposed from the foregoing observations that flies are simply and solely 
pests to man and beast, without any redeeming qualities. Their services are less required in 
cold and settled countries, but in warm climates their value as scavengers can hardly be 
over-estimated. As regards the removal of carrion alone, Linnaeus declared that the progeny 
of only three blow-flies would devour the carcase of a dead horse as quickly as a lion — a 
statement which, even if slightly exaggerated, conveys a vivid idea of their voracity and the 
rate at which they increase. 
Flies are also useful in keeping down the multitudes of destructive insects. Numbers of 
caterpillars fall victims to the bristly flies alluded to on the last page; and the Bee-flies, which 
form a family placed next to the Gad-flies, render far greater service in destroying locusts. 
They much resemble small humble-bees, being very much the same shape, and they are 
clothed with yellow down in the British species, and the transparent wings are conspicuously 
marked with black bands (as in the photograph above), or with brown shading and spots. 
The insects have a very rapid flight, and use their long proboscis to suck the honey of 
flowers; but their grubs are parasitic — at least in some instances — on wild bees; and it is 
probable that their resemblance to bees has some reference to this mode of life. But in 
Cyprus, Algeria, North America, etc., the larvm of allied species feed inside the egg-cases 
of locusts, sometimes destroying as large a proportion as four-fifths of the whole brood. 
Locusts have many enemies, but it will easily be seen that the attacks of foes like these 
must reduce their numbers considerably, notwithstanding the swarms w'hich frequently survive, 
and W'hich are liable to the attacks of other enemies, such as robber-flies, locust-birds, etc., 
after they have actually arrived at maturity. 
Nor must we omit to notice the use of flies as articles of food for man or useful 
animals. Many persons are very fond of cheese-hoppers, which are really the maggots of a 
small fly; and we read in Kirby’s “Textbook of Entomology,” page 92: “ The Rev. A. E. 
Eaton informs me that he believes that two species of EpJiemeridce (May-flies) form a portion 
of the so-called ‘ Kungu Cake,’ manufactured by the natives of South Africa of gnats, and 
probably any other insects which can be obtained in sufficient abundance.” “Gentles,” which 
are the maggots of flies, are used by anglers for ground-bait. 
