

173 



single brood in the north, while there are larva hatches it weighs about one-twen- 



two in the south. tieth of a grain ; in ten days it weighs one- 



Tlie color of the cocoon seems to be in- half of a grain, or ten times its original 

 fluenced in some way by the kind of food weight ; in twenty days it weighs three 

 eaten by the larva. Cocoons made by grains, or sixty times its original weight ; 

 larva which have been fed on hickory when a month old it weighs thirty-one 

 leaves have a darker color. In the true grains, or six hundred and twenty times 

 silk worm moth this same influence has its original weight, and has consumed 

 been noticed; larvae fed upon the vine about ninety grains of food; after fifty 

 producing red cocoons, on lettuce emer- days it weighs two hundred and seven 

 aid green cocoons, while those fed upon grains, or over four thousand times the 

 white nettle produce yellow, green or vio- original weight. At fifty-six days the 

 let cocoons. It is necessary in order to larva has eaten eighty-six thousand times 

 procure these results, that the larvae be its original weight in food ! It is there- 

 fed upon the mulberry till about twenty fore not surprising that these larvae can 

 days before the formation of the cocoon, often be easily detected upon trees by the 



Polyphemus. The life history of this large number of leaves which they have 



native silk worm (Telea polyphemus) is devoured. 



by far the best known, because many To provide for this great change in 



years ago it was very carefully studied size, the larva moults five times, but the 



with the hope that it would prove an im- time between these moults is not always 



portant silk insect. This hope unfortu- the same ; there is usually about ten days 



nately has not been realized. between the first four moults and about 



The moths, as shown by the plate, are twenty between the fourth and fifth. The 

 really beautiful ; the large eye spots on larva stops eating a day before the moult, 

 the hind wings contributing much to- spins a few threads upon the leaf to which 

 wards this effect. The transparent, win- it attaches its hind legs, and waits for the 

 dow-like centers in the eye spot are also- transformation, which usually takes- place 

 of quite rare occurrence among our in the afternoon. The larva, when ma- 

 moths. These transparent areas do not ture and ready to spin its cocoon, is about 

 possess the very minute scales found on three inches long. It is sometimes in- 

 the other parts of the wing. Almost all fluenced in its color by the food plant ; 

 of the wonderful variety of colors found the normal larva being of a golden green, 

 in the wings of butterflies and moths are although it has been known to show more 

 due either to coloring matter in these yellow coloring when found on red 

 scales, or to the breaking up of the white maple. 



light by minute lines on these scales, such A short time before beginning its 



as are seen in the play of colors on a cocoon the larva ceases to eat and selects 



soap-bubble. These fine lines on the a place for its cocoon. These cocoons are 



scales are only on the upper side, and are usually found upon the ground among 



about one-sixteen-thousandth of an inch the leaves, but are frequently attached to 



apart. twigs. After about a half day's work the 



The eggs of Polyphemus are very larva spreads over the inside of the 



much flattened, about the size of those of cocoon a gummy, resinous substance, 



Cecropia, and are deposited on leaves and which binds together the threads. After 



twigs singly or in small groups. These four or five days more of almost contin- 



liatch in about ten days and usually in the uous work, another coating is smeared 



morning. The young larva often devours over the inside, which renders the cocoon 



the shell which a few moments before af- practically air-tight. The silk fibres be- 



forded it shelter. This larva feeds upon come considerably finer as the cocoon 



oak, hickory, apple, maple, elm and a va- nears completion and the supply of silk 



riety of other trees, and thus has a larger begins to run low. For this reason the 



range of food plants than the Luna larva, inner layers of the cocoon are only about 



The rate of growth is prodigious, as has half as strong as the outer ones. The 



"been shown by Mr. Trovelot. When the larva, as the supply of silk diminishes in 



