INSECTS 11 



its inner surface ; so that, when the two parts are brought 

 together, they form a tube through which the butterfly sucks 

 nectar from flowers. When the 

 proboscis is not in use, the butter- 

 fly rolls it into a tight coil under- 

 neath the head (Fig. 9). 



10. Legs. The legs of a but- 

 terfly are not very strong, since 

 they are relatively so long and 

 slender. This is perhaps the reason 



why these insects seldom use them FIG. 9. Head of butterfly, 

 for walking. They are, however, 



very useful in clinging to flowers. The two curved claws 

 on the tip of each foot show clearly the means by which 

 the animals are able to hold on to the plants on which they 

 usually alight. 



11. Reproduction and life history of butterflies. As in 

 the reproduction of plants, the development of the butterfly 

 begins with a special cell known as an egg-cell. These egg- 

 cells are formed in the body of the female insect. When 

 these egg-cells have been fertilized by sperm-cells from the 

 male butterfly, which correspond to sperm-cells of the pollen 

 grains (P.B. 1 , 91), the eggs are deposited on the under side of 

 the leaves of plants on which the young can feed (Fig. 

 6). These egg-cells divide and subdivide, till at last a 

 many-celled organism is developed that is commonly called 

 a " worm," but that is more correctly known as a caterpillar 

 (Fig. 6). 



The tiny caterpillar emerges from the covering of the egg 

 and begins to feed upon the leaf. As it feeds it grows, and 



1 P. B. = " Elementary Plant Biology," by the authors of this book. 



