94 MODERN CLASSIFICATION OF INSECTS. 



mainder of the body. These larvae respire by tracheal branchiae, 

 placed either at the anus or along the sides of the body, under the 

 form of numerous small oar-like appendages. They quit the water 

 previous to becoming pupae, and construct an oval cell, in which they 

 pass the latter state a few inches beneath the surface of the borders 

 of ponds, &c., in which they had resided whilst larvae. 



Mr. MacLeay has remarked that aquatic insects do not differ so 

 much in form as terrestrial ; their numbers, as is especially the case in 

 the present stirps, are also very considerably less, and consequently 

 there are fewer genera amongst them, the exotic species being 

 for the most part congeneous with our own, offering, as Latreille long 

 ago remarked, " rien de remarquable ;" moreover the European species 

 are equal in size to, and occasionally larger than, those of tropical 

 regions, of which but few have been received by collectors belonging 

 to the larger and more typical genera ; indeed M. Lacordaire states 

 (^Ann. Sc. Nat., 1830.) that there are very few to be met with in 

 Brazil. It is also a curious circumstance that, whilst the Dyticidae 

 are so much inferior in point of numbers compared with the Carabidae, 

 the Gyrinidae are still less numerous in comparison with the former 

 of these families, Dejean enumerating 286 species of Dyticidae and 

 only 37 of Gyrinidae. The colours of these aquatic insects are 

 generally dark olive, black, or brown, variegated occasionally with 

 metallic tints and with markings of a dirty ochreous hue. 



This stirps comprises only two families, which are very distinct from 

 each other. MacLeay and Stephens, however, appear to regard the 

 genus Haliplus (Hoplitus Clairv.) as the type of a third family, and 

 which, from the small size of the insects and the structure of the ter- 

 minal joints of the palpi, seems most nearly allied to the Bembidiides. 

 Mr. Stephens, however, considers it to approximate rather towards 

 the genus Omophron. Messrs. Kirby and Spence propose for these 

 two families the names of Eunechina (swimmers), and Gyronechina, 

 (swimmers in a circle), adding that the larvae of the latter are the most 

 perfectly Chilopodomorphous, and those of the former the least so. 

 They have also added some valuable observations upon the affinities 

 of these and some other allied groups, which want of space alone 

 compels me to omit. (Vide Introd. vol. iv. p. 391-.) Adopting the 

 ordinary plan the two families will receive the names of — 



1st, DYTiciDiE (Diving-beetles) ; anterior legs short, antenuEe long. 



2d, Gyrinid.e (Whirl-wigs) ; anterior legs long, antennae short. 



