440 THE BIOLOGY OF INSECTS 



however, to find that this insect is the symbol of the ancient 

 kings of Lower Egypt, and it might be regarded as suitable 

 that a creature provided with a formidable sting should 

 stand in the hieroglyphs for a monarch powerful in war. 

 Flies are also depicted on the Egyptian monuments and 

 represented in amulets ; possibly this latter custom may 

 indicate some suspicion of the connection between insects 

 and human diseases. 



Much of this chapter has been devoted to the subject 

 of insects that are in various ways harmful to man's agri- 

 cultural and other industries as well as to his bodily health. 

 It is only fair, as we draw to a close, to pay some attention 

 to the insects which may be regarded as beneficial. Inci- 

 dentally it has been pointed out how insects that ravage 

 farm crops and garden plants and trees are preyed upon or 

 parasitised by other members of the class Thus, leaf- 

 eating caterpillars are pursued and eaten by predaceous 

 beetles, hunted by digging- wasps and buried as a provision 

 for their offspring, or devoured internally by the grubs of 

 ichneumon-flies. The common " Cabbage White " butter- 

 flies (Pieris) are kept in check by the small ichneumonoid 

 (Braconid) fly Apan teles glomeratus, whose white grubs, 

 when fully grown, make their way out of the Pierid 

 caterpillar in which they have fed (Plate XI, B) and spin 

 their oval, yellow cocoons around its dried cuticle. Plant- 

 sucking insects, such as aphids and cocci ds, are destroyed 

 in large numbers by ladybird-beetles and their grubs, by 

 the larvae of lacewings, and by the active maggots of the 

 hover-flies. We have seen how the result of the activities 

 of such predaceous insects has been demonstrated by their 

 introduction from one continent to another in order that 

 they may be used by human cultivators for the control of 

 pests, which have themselves been inadvertently introduced. 



Quite a large number of insect species in various parts 

 of the world have been brought in some way into the direct 

 service of mankind. Some races of men, for example, 

 habitually eat insects. According to D. Sharp (1899) an 

 Austrahan owl-moth, Agrotts spina, the Bugong, *' occurs in 



