MEMBRA GIDAE. 
205 
existed in historic time, all competent geologists assert that previous to the immediate 
glacial period, the monkey and the palm-tree occurred within the limits of the Arctic 
Circle, and thus we might expect that the fauna and flora of temporal climes would be 
represented in the two continents. 
When we pass away from Eocene times, we find that there are certain marked 
divisions of distribution over definite areas, and modern zoology indicates certain 
zones or districts, which will allow of a classified generalisation. 
With reference to the genera of the Membracidse it will be remembered, that up 
to the present time no corresponding traces of fossil insect life have been discovered, 
though singularly there is a fair abundance, in the rocks and sediments, of the casts or 
impressions of the kindred insect families of the Cercopidae, Fulgoridse, and Aphidiae. 
The genera previously described in this monograph belong almost exclusively to 
North arid South America, and they are singularly distinctive in their forms. The 
genera which follow belong, though not exclusively, to the Old World ; that is, to the 
continents of Europe, Asia, Africa, and Australia. They also are distinctive in form ; 
j'et not wholly so, for certain genera seem to overlap into America ; although probably 
the species now known there are not identical. 
Notwithstanding the fact that many Centrotidse are found in North and South 
America it will be convenient to keep the subfamilies Membracidse and Centrotidse 
separate. Their genera, however, sometimes intermix or assimilate in certain 
characters. Such may be seen in the genera Bocydium, Lycoderes, (Eda, and Hypsau- 
chenia, the diagnosis of which follow below, and which may be thought to be intro¬ 
ductory to the Centrotidse proper. 
Genus: (EDA. 
(Eda, Am. and Serv. Hemip. p. 540. Membracis, Fab. Smilia, Germ. Smilia, Westw. Ann. 
Nat. Hist. 1842. (Eda , Fairm. l.c. p. 505. 
This genus is remarkable from the large inflated pronotum which externally 
consists of a clear diaphanous horny membrane stretched over an elaborate net-work 
of veins. These nervures are disposed in the manner of a leaf in various stages of 
decay and colour, as yellow or reddish brown, and the pronotum has the appearance 
of a kind of balloon enclosing air only. The imitation of a leaf is very perfect, and 
sometimes even represents on the membrane the dark spots made by some insects on 
the surface, and so also the stalk from which the framework of the leaf-like neuration 
proceeds. 
The body of the insect is quite hidden, but the object of concealment is, as in 
most of the Membracidse, as yet unknown, though certainly it is in a manner protec- 
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