— Ill — 



The spring that this insect was studied here was a cold one ; 

 the average of the mean daily temperature from May 21st to 

 June 2 1 st being 6i° F. It was probably due to this fact that the 

 eggs did not begin to hatch till after the middle of June, which 

 was a month after the moths had been observed to pair. 



The larval history of this species is an unusually interesting 

 one. It was first traced out by Mr. Brunn ; and I cannot do bet- 

 ter than to give it in his own words : 



' ' The greenish colored eggs are laid scattering on the under 

 surface of the leaf. The eggs commenced to hatch June 16 or 17, 

 and the larva bored directly from the egg to the upper surface of 

 the leaf, where they made a small brown serpent mine. After 

 the larva leaves the egg the shell collapses and turns black. If 

 the egg shell be removed the circular opening made by the larva 

 entering the leaf can be seen. The mine is usually but 1 mm. 

 •(-g^iti.) broad at its largest end. Where the mines are abun- 

 dant on the leaf, it turns yellow and dies. On a small leaf I have 

 counted twenty or more mines. The frass is deposited along the 

 middle of the mine. When the larva has made a mine from 

 V2. to Y± in. long, which it does in from four to five days, it eats 

 its way cut through the upper surface, then somewhere on the upper 

 surface of the leaf it weaves a circular silken covering about -£% in. 

 in diameter. Stretched out on this network, the larva which is now 

 2.6 mm. long, makes a small hole in it near its edge, then, as one 

 would turn a somersault, the larva puts its head into this hole and 

 draws its body after. Arriving inside the molting cocooji as it may 

 be termed, on its back and doubled in the shape of a horseshoe, 

 the larva is then ready to strengthen the cocoon and close the 

 opening which it made in entering. The larvae make these 

 cocoons in from fifteen to thirty minutes ; and usually within a 

 couple of hours after leaving the mine. After the desertion of 

 the mine and before the making of these cocoons, the larvae eat 

 nothing, but may be found crawling over the leaves, stems and 

 branches, and often suspended by silk threads. On the 24th of 

 June many of the cocoons were empty, the larvae having molted, 

 leaving their cast-off skins in the molting cocoons and cut their 

 way out. The larvae remain in these cocoons in most cases less 

 than twenty-four hours. The larva before molting is readily dis- 

 tinguished from its later stages by its yellow color and a large 

 black spot on its first thoracic segment. After molting the first 

 time the larva becomes dark green and has a number of small 

 black spots on the first thoracic segment. 



After leaving the cocoon it commences to feed externally, 

 crawling everywhere and often suspended from the leaves by a 

 silk thread. While feeding it lies stretched out at full length on 

 the upper surface of the leaf, eating the upper epidermis and 

 parenchyma in small patches, but leaving the lower epidermis 



