Mmina.] CLAVICOBNIA. 375 



ELMINA. 



The members of this tribe are shorter and more ovate than the Parnina, 

 and their legs are, as a rule, longer in proportion ; the longer and regularly 

 formed antennae, and the absence of a trochantin to the anterior coxae, 

 will also distinguish them ; the species belonging to our genera are 

 aquatic in their habits, and are found adhering to stones or logs lying at 

 the bottom of running water ; their movements are very slow ; they 

 cannot swim, but they are enabled to cling to the stones to which they 

 are attached with great tenacity by means of their very powerful tarsi 

 and tarsal claws, thus, as Westwood observes, offering an admirable 

 instance of adaptive creation in the provision made for those insects 

 destined to live in violent running water, where, in fact, ordinary insect 

 motions, whether swimming or walking, would be completely paralyzed ; 

 the larva of Elmis has been described by Erichson (Naturgesichte der 

 Insect. Deutsch. iii. 524), and figured by Westwood (Classific. i. 113, 

 fig. 7, 16, 17), and Chapuisand Candeze (Plate iii., tig. 7) ; in outline it 

 somewhat resembles a peg-top, being very broad in front and strongly 

 narrowed behind, the apex being acuminate ; the head is very small and 

 sunk in thorax ; the antennas are very short, and the legs are concealed 

 beneath the body ; the thoracic segments are larger than any of the 

 abdominal segments, the sides of which are incised and overlap one 

 another in membranous lobes ; the whole form is shield- shaped, being 

 somewhat convex above and hollow beneath; Erichson thinks that the 

 shape serves to enable the insect to form a chamber for the storage of 

 atmospheric air on its under- side, but it would seem more probable that 

 it acts as a sort of sucker, and enables it to cling closely to the stones 

 to which it is attached. 



With few exceptions most of the genera of the tribe are found in 

 Europe ; Mulsant and Reitter divide the genus Elmis into four separate 

 genera, Elmis, Riolus, Latelmis, and Esolus, all of which are found in 

 Britain, as well as the genera Limnius and Macronychus ; the latter 

 genus has only been taken in one locality, and it is most probable that 

 Stenelmis at least will be at some future period established as British. 



I. Antennae 11-jointed, moderately long. 



i. Scutellum rather small, oblong or linear ; thorax not 



incised at base before scutellutn ELMIS, Latr. 



ii. Scutellum rather large, somewhat rounded ; thorax 



incised before Scutellum LIMNITTS, "Mull. 



II. Antennae 6-jointed, very short MAOBONYCHUS, Mult. 



EXiBXXS, Latreille. 



This genus contains about fifty species, of which about one-half are 

 European ; fifteen have been described from North America, a few from 

 Australia, and two from Chili and Peru, in which regions probably a 



