4 HOMOPTERA 



So far as the piesent evidence regarding the general relationship and phylogeny of the families 

 of the division Anchenorhynchi is concerned, we v^rould conclude that the Fulgoridte are the most highly 

 specialized of the families and considerably removed from the others in origin ; that the Cercopida, 

 Cicadellidie and Membracida, in that order, have developed from a common stem ; that the Aethalionida 

 have branched off from the membracid stem but now represent a distinct family, and that the Cicadida 

 are the lowest of all, with an origin considerably removed from the others. This arrangement may be 

 diagramatically represented as foUows : 



Fu/gor/dae 



Cercop/dcK 



C/cade/l/dae 



Membrac/dae 



Aetha//on/dae 



C/cad/dae 



FiG. I. — Phylogeny of tho Membraoida 



DISTRIBUTION 



The Membracida are primarily a tropical and subtropical family. Of nearly three hundred 

 genera recognized in the family, less than fifty are found in the temperate zones and none in the arctic 

 or subarctic regions. There seems to be little doubt but that the center of distribution of the group 

 was somewhere in a tropical region and that migrations have been first eastward and westward in 

 equatorial areas and that later the forms migrated northward and southward on the respective land- 

 masses of the eastern and western hemispheres, their limits of distribution depending upon the adap- 

 tibility of the species to environmental and particularly to climatic and floristic conditions. Records 

 of distribution from all parts of the world bear out such a hypothesis to a large extent and the 

 geological theories of land bridges and life zones in comparatively recent times, as used to explain 

 the appearance particularly of birds and mammals, are sufficient to account for earlier tropical migra- 

 tions. Unfortunately there is no paleontological evidence to support this assumption since no fossil 

 membracids have been discovered, although the closely related families of Cercopidm, Fulgorida and 

 Aphida are represented in paleontological Hterature. Buckton (iQoS) proposed the theory that previous 

 to the glacial period when « the monkey and the palm-tree occurred within the limits of the arctic 

 circle » the Membracida became distributed by a northern route. Since the condition which Buckton 

 postulates would place the period of migration sometime around the Eocene and since these land- 

 bridges would have been far to the north, his theory does not seem particularly attractive. 



The great home of the membracids at present seems to be South and Central America, with 

 equatorial Africa, southern Asia, and the East Indies offering hardly less abundant forms. According 

 to the present generally accepted faunal areas of the earth, the Membracida are represented as follows : 



Palearctic Region (Europe; the temperate parts of Asia limited by the Himalayas; the north of 

 Africa; Iceland and the islands of the Atlantic). 



Very poorly represented. Only three genera on the entire continent of Europe, but two species 

 in Great Britam, four species in Russia, a few representatives in Siberia and north China, and none 



