9 o 



THE STORY OF ANIMAL LIFE 



under very different conditions from the adult. 

 Fig. 24 shows two well-known instances of in- 

 sect larvae in which this is strikingly the case, 

 the larval form being a water-dweller, and the 

 adult a winged fly. Of these, one, the larvae of 

 the Dragon-fly, crawls about free; while the 



A 



FlG. 24. Larvae of insects. A, of a Dragon-Fly, enlarged ; B, 

 House of the larva of the Caddis Fly, natural size; C, the 

 Caddis Larva itself, enlarged. 



other, the so-called caddis-" worm," builds itself 

 a case of grains of stone and shell cemented 

 together. 



The second point of interest is the wonderful 

 part which has been played by insects in modi- 

 fying the world we live in. We owe the bright 

 colours and the sweet honey of flowers to the 

 selection exercised by insects; they carry the 

 pollen of flowers from one plant to its neighbour- 

 ing kindred, thus securing cross-fertilization for 

 the advantage of the plant, and thereby perpetu- 



