220 ANIMAL LIFE 



pond-weeds ; flies gain strength to travel where the 

 rising sap and filling nectaries, the warm blood of some 

 livestock or some less attractive nutriment, may give 

 them site and substance for their own needs and those 

 of their offspring. 



Week by week the life of the pond increases as the 

 dormant eggs therein hatch into the larvae of hover- 

 ing flies, and as the few hibernating aquatic larvae 

 become transfonned into the first dragon-flies of the 

 year. Then, as the fluttering, humming, and creeping 

 life is resumed, its first impulse is to provide, not for 

 itself, but for that which is to come, to find a place 

 where the young may be laid so as to reap the first- 

 fruits of the spring ; for now there is a new market 

 and but few competitors, and presently the blooms 

 will be gone, the enemies many, and the strife fierce. 



Thus the first spring brood makes its several 

 election of nesting-places. By some sense of smell, 

 and yet unexplained instinct, the butterflies and 

 moths, winter- worn or spring-fresh from their pupal 

 cases, deposit their eggs in little batches on or near 

 the food plant that the caterpillar needs. Each egg 

 is a minute, impermeable, sculptured vase, completely 

 enclosed in which is the germ of the future caterpillar. 

 In a week it will emerge gifted with as great a preference 

 for one plant rather than another, as though it had 

 a large experience and a matured decisiveness. Such 

 narrow taste in a new-born creature is, however, the 

 rule. As milk is the best and most acceptable first 

 food for our race, so, from the simplest worm up- 



