23^ KEPOET OF THE COMMISSIONER OF AGRICULTURE. 



before giving out the moth it becomes darker on the head, back, and 

 ■wing cases. In many important features it resembles the pupa of 

 L. hamadryadella, but differs in others. It is longer and more slender, 

 as was to be expected from the dilfering shapes of the larvae. The other 

 differences are just such as the differences in habits would lead us to 

 expect. The i>upa of L. hamadryadeUa has to cut its way through a 

 comparatively tough silken cocoon, as well as the upper epidermis of 

 the leaf, and hence we find that its forehead is armed with a iiromineut 

 beak furnished vntli a cutting and rasping edge, with marked serrations, 

 with which it easily v>'orks its way out. With Fitchella there is no cocoon, 

 but the lower epidermis of the leaf has to be cut; hence we find that the 

 beak is still present, but in a more rudimentary form than in the former 

 case, no serrations whatever being observable. The conditions in which 

 the latter is found, however, require a development of organs which the 

 former eitlier does not possess or which are only rudimentarily present. 

 These are appendages to hold it in i)osition in the midst of the network of 

 silken threads. The xuipa of L. liamadryadeUa has upon its last seg- 

 ment four very minute, outward-curved hooks, which serve to hold it in 

 position after it has worked its way half out of the mine, and while the 

 moth is emerging. In L. Fitchella these hooks are gTcatly lengthened, 

 and undoubtedly are of great use. In addition to these hooks, at the 

 juncture of the ])enultimate and antepenultimate segments of the body 

 there is upon each side a strong elevated ridge slightly directed back- 

 wards, which answers the same purpose, but the peculiar shape of which 

 arg-ues its development for some other purpose difficult to surmise. 

 Just below the beak on the ventral side of the body are six dehcate, down- 

 ward-directed hooks, and from the whole back and sides of the body pro- 

 ject a number of long, 'slender hairs, each having as its base a small 

 but distinct tubercle. These all seem to be provisions for the same end. 



The chrysalis at maturity takes almost precisely the same preliminary 

 stei)S to giving out the moth as did that of the last insect studied. It 

 works its Vay to the nearest wall of the mine, and, cutting through the 

 thin leaf skin, wriggles out until half of its body is in the open air. In 

 this position it is lirmly held, the anal hooks being entangled in the 

 loose silk within the mine, and the moth makes its exit through a longi- 

 tudinal dorsal split in the thoracic skin. 



The moth is very small, measuring only about T"""* (.27 inch) in ex- 

 panse of wings. Its general colors are white and bronze. These moths 

 may be often seen walking leismeiy about on the oak leaves through the 

 Kun'mier, their wings folded close to their body, and their long delicate 

 antennae in constant vibration. While in this position a white crescent- 

 shaped mark appears across the back, giving them a characteristic and 

 unmistakable look ; when tlie wings are spread, however, this crescent 

 resolves itself into two wedge-shaped marks, one on the lower border of 

 each fore wing. 



The time required for the development of the larva and the number 

 of broods in a season approximate closely to the coiTesponding points in 

 the history of X. liamadryadeUa. Dr. Fitch seems to have observed but 

 one brood in IsTew York, as he says : 



It is the latter part of summer -when these blister r,pot3 begin to appear on the oak 

 leaves. Thoy occur on the topmost leaves of the tallest tree?, as well as those that are 

 lower and near the ground. After the leaves have fallen in autumn a portion of these 

 blisters ^vill be found empty, v^hile others Imve pupae or sometimes larvae in them, 

 showiJig that the moths come out from them in autumn, and also in the spring. 



It seems to us that a safer conclusion would have been that the empty 

 mines did not necessarily indicate that some of the moths issued in late 



