MIOCENE FAUNA. 



In some parts of the Lake of (Eningen exhalations of poison- 

 ous gases probably took place, such as may still be observed in 

 various places (as near Tarasp in the Engadine) . By these the 

 insects would be killed when they fell into the water. This 

 notion is confirmed by the circumstance that the males and 

 females of several species of insects (Cydnus azmngensis, Pseudo- 

 phana amatoria, and P oner a veneraria, Heer (fig. 288), are found 

 united in the stone. 



The (Eningian collection of insects embraces many centuries, 

 and extends over all seasons of the year ; so that it probably lays 

 before us the majority of the forms that we require for the re- 

 presentation of the insect-fauna of that stage of the Miocene 

 period. 



A great number of wood-eating insects are found at (Eningen. 

 In the existing Swiss fauna the wood-beetles are to the rest of 

 the Coleoptera as 1 : 8*56, but at (Eningen they are as 1 : 3'3 ; 

 the (Eningian forests were therefore much richer in insects than 

 the existing forests of Switzerland ; and they afforded a shelter 

 on the whole to larger species. Stag-beetles were wanting; but 

 the gold-beetles (Buprestidse) were represented by a great num- 

 ber of species, which are among the largest and most abun- 

 dant beetles of the Miocene period. With them were associated 

 numerous Longicorn Beetles and Trogositidse. The larvse of 

 these Beetles doubtless lived under the bark and in the wood of 

 trees; the numerous Bibionidse which are found at (Eningen 

 passed their early life in mould and rotten wood ; and the little 

 dipterous mushroom-eaters (Mycetophagidae) were in the Agarics 

 which spread over the humid soil of the forest. The Termites 

 and the majority of the ants also certainly had their nests in the 

 forests ; and many species (such as Termes Hartungi and Euchn y 

 Formica procera, lignitum, and obesd) set up their dwellings, 

 after the fashion of their existing relations, in old trunks of trees. 

 Their business was to destroy dead plants, and to nourish them- 

 selves from dead animal substances, thus aiding in the perpetual 

 change of matter. 



Some insects climbed to the summits of trees, in order to 

 obtain honey-dew from the colonies of Aphides settled there ; 

 Chrysomelinous and Rhynchophorous beetles also dwelt on the 



