Biology of the Membracidae of the Cayuga Lake Basin 375 



swollen. This is followed by a cracking of the chorion al^out the neck 

 and the upper end — - that is, the end that leaves the ovipositor last and 

 is nearest the surface of the host. Some days may elapse after the first 

 splitting of the egg before the insect emerges. Finally the cap is forced 

 upward and the head of the nymph appears. The head is quickly followed 

 by the thorax and part of the abdomen. The nymph then appears to 

 rest for a few minutes, after which the legs are slowly withdrawn in order, 

 beginning with the first pair. At the same time the dorsal spines become 

 protruded, while the insect is still held by the posterior end of the abdomen 

 inside the shell. Finally this posterior end of the abdomen is pulled 

 out, and the nymph creeps a very short distance away from the old shell 

 and again rests. The entire time required for the emergence, from the 

 time the head is first seen until the process is completed, is usually about 

 half an hour. Hodgkiss (1910:88) has timed the process as from seven 

 to nine minutes, but this speed has not been equaled by any of the local 

 forms in the field. Wildermuth reports, for two specimens of Stictocephala 

 festina timed, a period of eighteen and twenty-eight minutes, respectively. 



INSTARS 



All the species studied show five nymphal instars. Miss Branch 

 (1913:84) reports only four instars for Entylia sinuata, but the nearest 

 local relative of the species, Entylia hactriana, shows the usual five. Riley 

 (1873) likewise observed that Ceresa taurina molted but four times before 

 reaching maturity. His report called the species Ceresa buhalus, but 

 it is now known that Ceresa taurina was the form he had in mind. This 

 species is abundant in the Cayuga Lake Basin, and in all cases studied 

 showed five instars. Each of the five instars is distinct enough to be 

 recognized, and displays characters sufficient not only for the recognition 

 of the species but also for the identification of the particular stage of 

 development that it represents. 



Li the first instar the nymph is of course very small, not greatly exceeding 

 in length the egg from which it hatched, verj' light-colored, and extremely 

 soft-bodied. Most nymphs have characteristic dorsal spines on thorax 

 and abdomen. In the first stage these spines are much inclined to be 

 complex and branched, and are numerous on the head and the thorax 

 with often more than one row on the abdomen. The head is very large, 

 out of all proportion to the body, and the legs are feeble. The eyes 



