396 ENTOMOLOGY 
studies, which we have already summarized. Moreover, para- 
sites of all degrees are attacked by predaceous insects, birds, 
bacteria, fungi, ete. The control of one insect by another 
becomes, then, a subject of extreme intricacy. 
Insects render an important, though commonly unnoticed, 
service to man in checking the growth of weeds. Indeed, in- 
sects exercise a vast influence upon vegetation in general. A 
conspicuous alteration in the vegetation has followed the inva- 
sions of the Rocky Mountain locust, as Riley has said; many 
plants before unnoticed have grown in profusion and many 
common kinds have attained an unusual luxuriance. 
As agents in the cross pollination of flowers, insects are 
eminently important. Darwin and his followers have proved 
beyond question that as a rule cross pollination is indispensable 
to the continued vitality of flowering plants; that repeated 
close pollination impairs their vigor to the point of extermina- 
tion. Without the visits of bees and other insects our fruit 
trees would yield little or nothing, and the fruit grower owes 
these helpers a debt which is too often overlooked. 
As scavengers, insects are of inestimable benefit, consuming 
as they do in incalculable quantity all kinds of dead and decay- 
ing animal and vegetable matter. This function of insects is 
most noticeable in the tropics, where the ants, in particular, 
eradicate tons of decomposing matter that man lazily neglects. 
The usefulness of the silkworms and the honey bee need 
only be mentioned, and after these, the cochineal insect and the 
lac insects. The ‘ Spanish fly ”—a meloid beetle—is still used 
medicinally, and in China medicinal properties are ascribed 
to many different insects. As human food, insects are of con- 
siderable importance among semi-civilized races; the migra- 
tory locust is eaten in great quantities in Africa, and termites 
in Africa and Australia, the latter insects being said to have 
a delicious flavor; in Mexico the eggs and adults of an aquatic 
hemipteron, Corixa, are highly relished by the natives... As 
food for fishes, game birds, song birds and poultry, insects are 
of vast importance, it is needless to say. 
