CORNELL. UNIVERSITY EXPERIMENT STATION BULLETINS. 209 



its stages which might be of interest, or of aid in combating the insect. 

 The breeding was done in the insectary, and field observations were made 

 to verify the results as far as possible. The cages used consisted simply 

 of a common lamp chimney set on the surface of the soil in a small flower 

 pot; the top of the chimney was covered with Swiss muslin and a vial of 

 water sunken into the soil kept the pear branch fresh for several days. 

 These cheap and simple cages have been found very convenient and useful 

 in breeding such small insects, or in getting the number of moults of larvae 

 isolated in them. 



The females of the spring brood began to appear about June 10, 1892, 

 and many were laying eggs by the 20fch. On the 2l8t, several females 

 were placed in cages on uninfested pear leaves. Eggs were laid the fol- 

 lowing day. When first laid they were tender and easily crushed; but in 

 a few hours the shell became hard and the egg could be dislodged and 

 quite roughly handled without injuring it. The shell was found to be 

 impervious to several oils and weak alkalies. The acids and strong alka- 

 lies penetrated the shell and killed the embryo. The eggs hatched in from 

 «ight to ten days; a day or two before hatching the crimson eyes of the 

 embryo could be plainly seen through the shell near the larger end of the 



egg. 



The nymphs which emerged were oval in form and of a pale translucent 

 yellow color with the abdomen more opaque and darker. The crimson 

 eyes were large and distinct. The curious creatures were scarcely visible 

 to the unaided eye, measuring only .013 of an inch in length. A slight 

 constriction of the body marked the beginning of the abdomen which is 

 fringed with eight or nine long and several short hairs. The wing-pads 

 were not yet distinguishable. The antennae had but three joints, two short 

 basal and a long terminal joint tipped with two long bristles. The short 

 stout legs terminated by minute claws enabled the nymphs to soon find a 

 suitable feeding place. Several nymphs were immediately transferred to 

 other cages, only one being placed in each cage. The next day the loca- 

 tion of the nymph was often readily determined by a globule of honey-dew 

 several times larger than the little creature which had secreted it. After 

 feeding thus for six or seven days the nymphs become too large for their 

 skins which burst open along the middle of the head and back and the 

 insect crawled forth clothed in a new and elastic* skin that had formed 

 beneath the old one. After thus moulting the nymph usually sought a 

 new feeding place, leaving its old shriveled skin attached to the globule of 

 honey-dew it had secreted. 



In their second stage the nymphs increased about one third in size, but 

 were of the same general color except the tips of the antennae which were 

 black. There were four joints in the antennae, a division of the third 

 taking place at the moult. The segments of the abdomen were more 

 distinct and the wing-pads were developing. The nymphs remained in 

 this stage about four dayS; when the second moult occurred. 



At the third stage the nymphs measured .027 of an inch in length. The 

 wing-pads were larger and blackish; and the other black markings which 

 distinguish the full-grown nymphs were faintly outlined. Six or seven 

 joints were now distinguishable in the antennae, the last three being black. 



About three days later, the third moult occurred. The nymphs differed 

 from those of the third sta^e in having eight antennal joints; the wing- 

 pads were larger; the nymphs were .038 of an inch in length; and the eyes 



