NO. 6 CATERPILLAR AND BUTTERFLY — SNOUGRASS 45 



the leaves, where they enclose themselves in cases formed of cut-out 

 pieces of leaves, but they do not swim. 



Butterflies have many natural enemies, including entomologists 

 with collecting nets, but those of northern and temperate regions that 

 survive the summer may be still plentiful at the end of the season. 

 In the fall or early winter when cold weather comes on most of them 

 simply die a peaceful death. Hardy individuals of some species, such 

 as the mourning-cloak butterfly Nymphalis antiopa, however, live 

 through the winter under logs or stumps lying on the ground, and 

 the monarch butterfly imitates the birds in flocking south for the 

 winter. 



For the others, both moths and butterflies, nature has made some 

 provision for carrying their species through the winter in an immature 

 stage. Perhaps most commonly it is the pupa that hibernates, but with 

 some species the caterpillar lives through the winter, or the winter is 

 passed in the egg stage. The overwintering caterpillar is usually 

 within the protection of a cocoon, but the brown woolly bear hiber- 

 nates in a covering of its own wool, and young tent caterpillars remain 

 in the egg shells. The female moth of this species, Malacosoma ameri- 

 canum, lays her eggs in late spring attached to a twig of a favorite 

 tree of the caterpillar, and covers them with an impervious coating of 

 material from the accessory glands of her reproductive system. 

 Within three weeks or a little longer the young caterpillars are 

 fully formed in the eggs. Here they remain protected under the egg 

 covering through the summer, fall, and winter to emerge early the 

 following spring. 



It is interesting to note how the lives of insects in northern regions 

 have become adapted to the alternation of winter with summer. By 

 contrast, tropical species can go on indefinitely as a succession of 

 broods without interruption. The northern insects, therefore, have 

 undergone a special evolution to meet the condition of survival 

 imposed upon them. Even within a single order such as the Lepi- 

 doptera different species have solved the problem of survival in 

 different ways. 



REFERENCES 

 Ammann, H. 



1954. Die postembryonale Entwicklung der weiblichen Geschlechtsorgane 

 in der Raupe von Solcnobia triquetrella F. R. (Lep.) mit ergan- 

 zenden Bemerkungen iiber die Entstehung des mannlichen Ge- 

 schlechtsapparat. Zool. Jahrb. Anat., vol. 73, pp. 337-394, 37 figs. 

 Babers, F. B., and Woke, P. A. 



1937. Digestive enzymes in the southern armyworm. Journ. Agr. Res., 

 vol. 54, No. 7, PP- 547-550. 



