284 Insects and their Surroundings 



tree we can bring down a shower of Beetles, 

 Caterpillars and Plant-bugs. And search in more 

 concealed situations will reveal yet other insects. 

 Underground, grubs are devouring the plant roots, 

 while pups lie in their cells awaiting their final 

 change. Beneath stones lurk Ground-beetles, which 

 as soon as night falls will sally out in pursuit of 

 prey. Under the bark or within the v/ood of many 

 trees are burrowing the grubs of Beetles, while 

 the caterpillars of tiny Moths eat out their winding 

 tunnels within the tissues of the leaves. 



Insects then have achieved a remarkable degree 

 of success in the " struggle for existence." This 

 is due largely to their perfect locomotion, and especi- 

 ally to their power of flight. In structure they 

 have reached the highest point possible to the 

 arthropodous type. The specialised head with its 

 beautiful sense-organs ; the reduction of the legs 

 to three pairs, giving rapidity and certainty to the 

 motions of the body, and affording in the double 

 tripod the best mechanical base of support ; the 

 presence of wings, and the moderate abdomen 

 never too bulky for easy carriage, — all contribute 

 to place Insects pre-eminently above other arthropods. 

 The blood and air-systems of insects, too, favour a 

 life of abundant energy, the blood directly bathing 

 all the tissues and receiving fresh oxygen at once 

 in all parts of the body through the remotely 

 branching air-tubes. The diversity of ways in 

 which insects are able to feed has also largely 

 contributed to their success in life ; and by the 

 very general adoption of metamorphosis the same 

 individual often comes to feed in different ways in 

 the successive stages of its life-history, an obviously 

 economical arrangement for the species, since the 

 drain on each of the various food-supplies is lessened. 



