Biology of the Membra cidae of the Cayuga Lake Basin 373 



laying season for each brood, tho, as has been remarked in connection 

 with other points in the hfe history, the overlapping of broods makes 

 such seasons difficult to delimit. The earliest field record for the process 

 is May 11, for Eniylia hactriana, and the latest is November 10, for 

 Ceresa basalts. 



Species 



Number of eggs in egg mass 



Average 



Mode 



Enchenopa binotata. . . . 



Ceresa diceros 



Ceresa bubalus 



Ceresa taurina 



Ceresa borealis 



Stidocephala inermis . . . 



Carynota mera 



Thelia bhnaculata 



Telamona reclivata 



Telamona querci 



Telamona arnpelopsidis 



Cyrtolobus vau 



Ophiderma pubescens . . 

 Vanduzea arquata 



The eggs are generally white or pearly, club-shaped or tooth-shaped, 

 and about 1.5 millimeters long by 0.3 millimeter wide at the maximum 

 diameter. The largest egg found locally is that of Thelia bimaculata, 

 which averages 2.6 millimeters in length and 0.6 millimeter in diameter; 

 the smallest is that of Puhlilia concava, which measures 0.7 millimeter in 

 length and 0.17 millimeter in diameter. The egg may be smooth or 

 sculptured, the base usually being rounded and the tip pointed. In the 

 eggs of most species a distinct neck is visible, often grooved. The chorion 

 is usually vitreous. The micropyle in most cases is oval, opening tan- 

 gential to the longitudinal axis. The cap is comparatively large, and 

 before hatching becomes swollen and wrinkled. The lateral margins of 

 the egg are curved, one side often being more convex than the other. 

 Just before the eggs hatch they become slightly larger. 



