INSECT LIFE 173 



charmed twilight. Granting that the butterfly opens 

 and shuts its proud wings to draw attention of 

 possible mates utility and that these winter gnats 

 dance in male parties to commend themselves to the 

 other sex utility it is still possible to think that 

 other motive comes in, and that amusement or 

 pleasure for its own sake is this motive. Birds sing 

 to draw mates utility but often there are other 

 motives in singing, and one of these surely is pleasure 

 for pleasure's sake. 



I leave utility, and turn back to these summer 

 sylphs, whose every movement seems to argue that 

 beauty and pleasure are paramount. Save for their 

 impulses of migration, most butterflies are essentially 

 home-stayers. An acre of ground is enough and to 

 spare for a butterfly, enough for a moth. The 

 sallow on which the purple emperor fed in its grub 

 stage of life may serve as its throne when the chry- 

 salid grows into the perfect insect. A few yards of 

 ground are enough for the small heath or the large 

 heath butterfly, if it has a few flowers to draw nectar 

 from, a bent or a grass-head for a night couch, and 

 the plant-food at hand for its caterpillar descendants. 

 The marbled-white is another home-stayer. But this 

 beautiful butterfly is curiously local, not only as indi- 

 vidual, but as species. I forget what the caterpillar of 

 the marbled-white feeds on, but it is a plant that 

 grows in abundance in thousands of places where 

 never a marbled- white is seen. With a fastidiousness 



