240 Agricultural Experiment Station, Ithaca, N. Y. 



tlie full-grown nymph is described on page 233. The black mark- 

 ings are represented in Figs. 1 and 2. 



After feeding five or six days, the nymphs moult for the last 

 time; at this moult the adult insect crawls from the nymph's 

 skin. European observers have recorded but four moults for the 

 nymphs of several species of Psyllidae. The observations at the 

 insectary were made upon several individuals isolated in small 

 cages which were under daily observation from the emergence of 

 the nymph from the egg to the appearance if the aduli insect. 



In each stage the nymphs secreted globules of honey-dew sev- 

 eral times larger than themselves; sometimes the globules com- 

 pletely enveloped a nvmph. After each moult the nymphs usu- 

 ally sought a new feeding place, leaving the old skin attached to 

 the drop of honey-dew. The old moulted skins, of thi last 

 moult especially, often retained their form almost perfectly. So 

 life-like did some of them appear, with the legs and antennae 

 naturally placed, that it often required close examination with a 

 lens to determine whether the object was a live nymph r)r only 

 the cast-off garment of one. 



The whole life cycle of the generation studied, from the laying 

 of the egg to the appearance of the adult insect, was about one 

 month. The adults upon emerging are of a delicate grei'nish 

 color; the blackish markings soon appear, however, and in two 

 or three days the green changes to the normal reddish brown 

 color. Although the adults are so distinct sexually, there seems 

 to be nothing but the full-grown nymphs which would indicate 

 the sex of the adult soon to emerge from the nymph's skin. 



The adults begin feeding at once after emerging but do not 

 increase visibly in size. They appear to secrete no honey dew 

 but void considerable quantities of a whitish excrement. Adults 

 of the summer broods lived for several days in cages in the 

 insectary; how long they live under natural conditions has not 

 been ascertained, probably less than a month. The adults which 

 hibernate, however, remain alive for at least six months. 



About a week after the summer broods of adults emerge, 

 copulation takes place and the deposition (-f eggs soon begins. 

 The winter brood, as has been said, do not, however, copulate and 



