39^ ENTOMOLOGY 



studies, which we have already summarized. Moreover, para- 

 sites of all degrees are attacked by predaceous insects, birds, 

 bacteria, fungi, etc. 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. 



