NO. 6 CATERPILLAR AND BUTTERFLY — SNODGRASS 43 



emerge into the air. In some cases the caterpillar is activated by an 

 instinctive foresight and either leaves the head end of the cocoon very 

 weakly woven, or makes a hinged door that the moth can open. 



Those moths that on escape from the pupa find themselves still 

 imprisoned in a closed cocoon are confronted with the problem of 

 how to get out. Help comes from an unexpected source. In these 

 species the shrunken silk glands of the larva now secrete a clear 

 liquid, which issues from the mouth of the moth and softens the 

 adhesive coating of the cocoon threads, thus enabling the moth to 

 push its head through the end of the cocoon and escape. Trouvelot 

 (1867) described the pre-emergence activities of Telea polyphemus 

 as seen through a mica window inserted into the side of the cocoon. 

 When the moth is fully formed within the pupa it becomes highly 

 active and soon splits the pupal skin over the thorax. The head and 

 legs are at once disengaged and the solvent liquid flows from the 

 mouth. The insect now waits for the liquid to take effect on the 

 cocoon. Then it makes strong contractions and extensions of the body, 

 which force its head through the moistened silk. The strands separate, 

 spread apart, and the moth issues without breaking a fiber. 



Some of the moths and many of the butterflies are the most beauti- 

 fully colored of living things, their only rivals being among the birds 

 and the flowers. With the birds it is principally the males that are 

 endowed with beauty, and for the utilitarian purpose of attracting 

 the females. Of the flowers, it has been said that many are born to 

 blush unseen and waste their sweetness on the desert air, but the poet 

 did not know that the flowers too have a practical reason for both 

 their perfume and their color, which is to attract the pollinating 

 insects. The Lepidoptera, on the contrary, seem to make no use of 

 their ornamentation. Though in many species the males are more 

 brightly colored than the females, it is the males that are attracted to 

 the females, and not by the charm of color in this case, but by odor. 

 Kellogg (1907) has shown that the male of the silkworm moth finds 

 a female entirely by her scent. The scent glands are eversible from 

 the last abdominal segment of the female. When the glands are cut 

 off, the male reacts as strongly to the glands themselves as to an intact 

 female, and entirely ignores a female deprived of her glands. The 

 silkworm moths cannot fly, but the males of some other moths are 

 well known to be attracted to the females from long distances. The 

 males themselves of many butterflies produce scents, some of which 

 are attractive, others repellent. 



If color plays no important part in the lives of moths and butterflies, 

 except in the case of protective imitation and mimicry, it is difficult 



