202 DARWINISM AND THE PROBLEMS OF LIFE 



insects ; the butterflies with the largest probosces would 

 have the advantage because they would find most food^ 

 and their ova and seed would be the most vigorous. 

 Thus the characters would mutually affect each other. 



It is not only the proboscis of the butterfly, but also 

 the mouth-parts of other insects, that have been modified 

 by a correlative selection with the calices of flowers. In 

 the ancient insects the eating organs consisted of mas- 

 ticators, as we still find in many orders, such as the 

 locusts, moths, and beetles, because they chew their 

 food. But in the bees a part of the mouth was converted 

 into a long licking tongue ; and in the butterflies two 

 masticators have blended to form the long tube of the 

 proboscis. 



In other insects there have been different modifica- 

 tions of the mouth-parts. The masticators of the gnats 

 have been converted into long stilettoes. The larvae of 

 the dragon-flies, which live in the water, have developed 

 the lower parts of the mouth as pincers, with a long 

 retractile stalk, and able to seize an animal at some 

 distance when they are suddenly thrust out. We 

 should never come to a stop if we were to examine 

 all the adaptations of the mouth-parts of insects. We 

 will desist, however, and briefly consider the other parts 

 of the insect body. 



The wings have entirely disappeared in the flea ; in 

 the fly the back pair has degenerated, and in the 

 strepsitera^ the front pair. In the earwig the wings 



^ The strepsitera, to which belongs, for instance, the " Sty lops 

 melittae," have some peculiar adaptations. The larvae, which jump- 

 briskly on their six legs, force their way into the bellies of bees and 



