INSECTS 49 



case without interrupting one another, But those dependent 

 on the seeds of the water-mallow, and other rarities, have 

 certainly a difficult matter to perform. It must, however, be 

 remembered that in the struggle the strongest usually wins, 

 and therefore its case is continually becoming longer and 

 larger until finally completed. So that in an order of succes- 

 sion of strength all the cases are gradually finished, and the 

 weakest, presuming that it has not been eaten by fishes, water- 

 beetles, or other enemies in the meanwhile, is at length able to 

 accomplish its purpose. 



Under suitable conditions a caddis-worm will take between 

 four and eight hours to build and complete a case. Each stick 

 or stone, or whatever it may be, is woven by silk to the next 

 piece, so that when the case is finished the caddis-worm lives 

 in a silk-lined structure. Each stick is carefully cut to the 

 right length before use, or sometimes is used and the non- 

 required part is subsequently cut off. The cases are usually of 

 a larger diameter at the head end. 



The larva, which is a most voracious feeder, must necessarily 

 grow, and as it does so the case naturally becomes too small 

 for the tenant. The little creature shows evidence of common 

 sense, for it neither bursts the case by remaining in too long, 

 nor evacuates it and builds another, but systematically adds a 

 fresh part to the front, and cuts off a portion towards the end. 



That the larva should be so eager to build a case is little to 

 be wondered at, for every fisherman knows that the caddis 

 minus its case is a most pleasant sight to all fish. The wily 

 trout and the lowly perch forget their social positions, and bite 

 without more than a glance, for the caddis-worm larva has 

 a soft whitish or greenish body of so tempting an appearance 

 that few things of a carnivorous disposition could refrain from 

 attacking it. Although the head and thorax are protected by 

 chintinous material, yet it is only by frequently and rapidly 

 dodging into the case, which allows nothing large to enter, 

 that the much-chased " worm " contrives to reach its pupa 

 stage. That the caddis is fully aware of its danger is evident 

 to those who have studied it, for it shows the greatest 

 concern in keeping its body in the safety of the case. 



Caddis-worms wander slowly over the bed of the pond or 

 stream and climb up amongst the vegetation. Their diet 

 depends on species and circumstances ; they are mostly vege- 

 tarian a few varieties are carnivorous ; but should, however, 

 food be scarce the vegetarian forgets the morals of the case so 

 far as to turn into a cannibal, tearing open the cases of its 

 victims, and demolishing the owner without remorse. 



D 



