Biology of the Membracidae op the Cayuga Lake Basin 405 



Thelia himaculata and Vmiduzea arquata are usually found together on 

 locust; the individuals are incUiied to crowd in dense groups, often with 

 the bodies toucliing and in some cases even one upon another, specimens 

 of both species being in close harmony. Each of these species shows the 

 same gregarious habits when the other is not present. Enchenopa bmotata 

 found on the same host is prone to cluster together as individuals, but not 

 to such a noticeable extent as the two other species, and they are seldom 

 found living with other Membracidae, Most of the species of Ceresa, 

 particularly Ceresa dicer os, show the same habits; the adults are found 

 in rows or groups on the stems and the nymphs are usually grouped. These 

 species, however, seldom congregate with other forms of the family. 

 In the same manner the Telamonas live together as individuals of a species 

 but seldom as species of a genus or with other genera. Entylia hactriana 

 and Publilia concava are decidedly gregarious and are found in dense clusters 

 on their respective hosts. The two species have not been found Kving 

 together, however, and this fact is additional evidence toward the proof 

 that the forms are not so close together taxonomically as has been supposed. 

 Micrutalis calva, while rare in this basin, has been reported as living the 

 same communal life (Matausch, 1912 b), while most species of Stictocephala, 

 Platycotis, and Vanduzea in this country are known to have like habits. 



By this commimal life is not meant any sort of division of labor, as is 

 usually understood by the term as applied to certain Hymenoptera, but 

 simply the habit of living together in colonies, the nymphs and the adults 

 congregating in clusters or groups while feeding or resting (Plate xliii, 1). 

 So far as is known these habits have no significance beyond the mere indica- 

 tion of gregariousness. No actions have been observed which would 

 tend to show that the individuals were mutually beneficial to one another 

 in any way or that the community life affected in any manner the usual 

 life history of the individual. It is interesting to note, however, that 

 most of the species which lead such hves are attended Ijy ants. It is easy 

 to imagine that insects living in colonies may be more easily located by 

 the ants than solitary species, but it is not beheved that the ants have 

 anything to do with the keeping of the individuals of the colony together. 



It may be noted, also, that the individuals of certain species, such as 

 Ceresa buhalus, live together as nymphs but separately as adults; this is no 

 more than the natural result of the hatching of an egg mass and the 

 subsequent scattering of the members. Other species are solitary and do 



