276 



NATURAL HISTORY. 



Fig. 271. — Cocoon of the American silk-worm. 



four thousand times, or to over two hundred grains, having eaten in that 

 time three-quarters of a pound of oak-leaves. If it were not for numerous 

 enemies, how quickly these would strip our forests of their leaves. 



One experiment tried by Mr. Trouvelot was very interesting. Every 

 naturalist receives numerous parcels of insects, the boxes being perforated 



to allow the animals to breathe. How 

 needless this is, is seen from the follow- 

 ing : " Having observed how clear and 

 air-tight the cocoon of the Polyphemus 

 seemed to be, I could not conceive that 

 air was necessary for it to breathe. 

 Desirous of ascertaining whether my idea 

 was correct, I took three cocoons, and at 

 two different times I covered them carefully with a thick coating of starch, 

 allowing the first coating to dry before putting on the second one. After 

 this the cocoons were covered at three different times with a heavy coating 

 of shellac varnish ; thus the cocoons were made perfectly air-tight. They 

 were kept in a cold dry room all winter. In July the moths came out per- 

 fectly healthy, the fluid they discharge through the mouth having dissolved 

 the starch and varnish. So these insects had been nine months with no 

 air, except the very small volume enclosed in the cocoon, and they had 

 accomplished their transformation just as well as if the air had been 

 allowed to come into the cocoon." 



The pale green luna-moth is the only other species of native silk-worm 

 that we need mention, and, in the writer's opinion, is far the most beautiful 

 member of the group. The hind wings are produced into long and slender 

 tails, while the delicate green of these organs of flight is enlivened by eye- 

 like spots — transparent in the centre, and margined with white, yellow, 



red, and black — one spot 

 in each wing. The larva 

 of this beauty is fond of 

 the leaves of the walnut 

 and hickory. 



Allied to these silk- 

 worm moths are a large 

 number of other showy 

 forms ; to even catalogue 

 them would take more space 

 than we can afford. Some 

 are very common, flying 

 about at dusk on summer evenings ; while others are so rare that they are 



Fig. 272. — Io moth (Hyperchiria io). 



