ADAPTATIONS TO HAUNTS AND SEASONS 271 



long and powerful hind-legs, they leap into the air, not 

 alighting again until a great distance has been cleared. 

 The compression of the body that characterises them is 

 clearly suited to their movement by great vertical jumps. 

 It is interesting to notice the same modification of form 

 carried to an extreme degree in those well-known parasites 

 the fleas — wingless but obviously related to winged insects — 

 whose bodies are so compressed as to be three times as deep 

 as broad (Fig. 67, c, d). They also are active vertical 

 leapers, their agility affording them the chance of getting 

 on to fresh hosts, and in this respect they afford a most 

 interesting because independent parallel to the grasshoppers, 

 and a striking contrast to the bugs, which are like them- 

 selves parasites. 



A form of body cylindrical or approximately so, is 

 familiar in many insect larvae such as caterpillars and 

 maggots. In a caterpillar (Fig. 45) this shape together with 

 the support afforded by legs and pro-legs all along the 

 body-length is well-suited for crawling and feeding along 

 twigs or leaf-edges, as well as on leaf-surfaces. Among 

 maggots and grubs generally the rounded form of body, 

 whether cylindrical or tapering, is adapted for burrowing 

 in the plant tissues or refuse which furnish the food supply 

 of so many insect larvae of diverse orders. Among adult 

 insects the cylindrical body is especially characteristic of 

 wood-borers. The well-known " shot- hole " borings in 

 old furniture and timber roofs indicate the presence of 

 Ptinids (" death-watch ") beetles which live in tunnels 

 excavated in the wood and feed on the material thus bitten 

 away. These beetles are all approximately cyHndrical in 

 body form, and a similar shape is noticeable in beetles of 

 other families which practise the same manner of life. Of 

 these the Bostrychidae are akin to the Ptinidae, but the 

 Scolytidae, or bark-beetles (Fig. 49), like those in general 

 aspect, are distinguished by many important structural 

 characters, and belong to a distinct group of the order. 

 We notice here again, therefore, independent and parallel 

 modification of form in two or three different families in 



