WATER-BUGS. 51 



not be compared with any belonging to the existing fauna. The 

 genus NabiSj however, presents an indigenous form (fig. 308), 

 several species of which were distributed over the Miocene land. 



The Hydrometrae (Hydrodromici) form a small family of thin- 

 1 egged insects, which live on the banks of ponds and lakes in the 

 reeds and sedges, and run with great agility upon the surface of 

 the water. From (Eningen Prof. Heer has a species (Limnobates 

 prodromus, Heer) which may be regarded as the precursor of L. 

 stagnorum, Linn., a species which is often seen in Switzerland. 



The tribe Hydrocorae (water-bugs) is represented at (Eningen 

 by the families of the Nepinae (water-scorpions) and Notonectae 

 (boat-flies). The former includes five, and the latter a single 

 species. The latter is &Corisa resembling an American species. 

 Of the Nepinae there are forms of Nepa and Naucoris such as 

 occur in the Swiss fresh waters ; but side by side with these are 

 found the tropical and subtropical genera Belostoma and Diplo- 

 nychus. The latter is represented only by one species (Diplo- 

 nychus rotundatus, Heer) , which has its nearest relative in India ; 

 the former by a truly gigantic insect (Belostoma speciosum, Heer, 

 fig. 303), rivalling in size the largest of the tropical Rhynchota, 

 the great Belostoma of Brazil, and so closely approaching it even 

 in appearance that the Miocene species may be regarded as pro- 

 bably the ancestor of the Brazilian insect. A similar species 

 has also been discovered in the lignite of Bonn, so that the type 

 now found in America was formerly in all probability diffused 

 over the whole of Europe. The Belostoma are rapacious animals, 

 the females of which carry their eggs about with them. (Enin- 

 gen has become remarkable for producing gigantic forms, not 

 only among the water-beetles, but also among the water-bugs. 



The Cicadinae have quite a different appearance both from the 

 land and the aquatic bugs; they are harmless and generally 

 small insects, which are distributed in great numbers over all 

 countries, and live exclusively upon the juices of plants. They 

 are divided into four families, all of which existed in Tertiary 

 times. Of the singing Cicadas a large species (Cicada Emathion, 

 Heer, fig. 304) occurs at (Eningen. It closely resembles the 

 Cicada of the ash (Cicada Orni, Linn.), which is common all 

 over the south of Europe, occurring even in the Valteline, on the 

 lake of Corno, in Ticino, and in the Valais, and found upon the 



