Biology of the MembrAcidae of the Cayuga Lake Basin 415 



would of course affect the number of broods per season, and a variation 

 in number of broods might in turn change all the dates for the following 

 year. Thus the various phenomena in the life history of the insect are 

 so closely bound together that the change of one condition may result in 

 .the upsetting of the entire structure of hypotheses in which this condition 

 entered as a factor. It is not unreasonable to suppose that all the con- 

 ditions that have been discussed, as well as many others on which no data 

 have been obtained — such as sap conditions in the food plants, pathologic 

 conditions in the insects themselves, and the like — enter into this complex 

 ecology of which the foregoing can be considered as offering only the 

 roughest suggestions. 



ENEMIES 



The Membracidae seem to have but few natural enemies and against 

 these enemies the insects have a number of valuable methods of protection. 

 The field notes show surprisingly few cases in which membracids have 

 actually been seen taken by other animals or killed by natural foes. 



parasites 



Parasites are found on both eggs and adults. The egg parasites are 

 common on the eggs of most species of the genera Ceresa, Stictocephala, 

 Telamona, and Vanduzea. These in most cases are Chalcididae and only 

 a few have been determined. A detailed study of this egg parasitism 

 which has been made by the writer for an African species, Oxyrhachis 

 tarandus, and which is to appear as a separate report, as well as observa- 

 tions on local forms from which the parasites were reared, seems to show 

 that the method is the same in all cases. The parasite deposits its egg in 

 the newly laid eggs of the membracid and passes its larval and pupal 

 stages within the egg. On maturing, the adult hymenopteran emerges 

 by breaking open the cap of the eggshell, which has meanwhile become 

 discolored or l3lackened. The oviposition of the chalcid has not been 

 obsei-ved for any of the local species, but parasitized eggs have been found 

 from which the parasites have been reared. The only parasite thus reared 

 locally has been Polynema striaticorne Gir. Miss Murtfeldt (1890) 

 credits an undescribed Polynema with having destroyed membracid eggs 

 in Missouri, and Hodgkiss (1910:91) states on the authority of Girault 

 that the species in question was the same species and that it has been ])red 

 from eggs of Ceresa buhalus at Geneva. Apparently this is a common and 



