COLEOPTERA PARNID^. 117 



In his early works, Latreille, from the resemblance between the 

 antennee of the typical genus Parnus and that of the Gyrinida;, formed 

 these two groups into a section, which he termed Otiophori ; subse- 

 quently, however, he was convinced that the relationship between them 

 was not a direct affinity, and they were accordingly removed to their 

 proper situations. 



The European genus Potamophilus (G. Hydera Latr. ; P. acuminatus, 

 F. Pz. vi. 8.), although exhibiting the elongated form of Parnus, 

 differs in having the antennae 11-jointed, the second joint being large, 

 but not internally produced ; these organs are not received into cavi- 

 ties on the underside of the head ; moreover, the mouth is not con- 

 cealed beneath by the dilated anterior margin of the prosternum. 



The subfamily Ehnides* (fam. Limniidae Stephens^ is distinguished 

 from the preceding by the shorter and more ovate form of the insects 

 of which it is composed ( fig. 7. lO. Elmis agneus), and by the longer 

 and more regularly formed antenna: (^fig. 7. 13.), the basal joints being 

 smaller than the following. These curious little insects have been 

 regarded as allied to the Byrrhidae and Histeridre, but they are most 

 evidently related to the Parnides. 



The species of the genus Elmis are aquatic in their habits, being 

 found adhering on the undersides of stones lying at the bottom of run- 

 ning water. Their motions are very slow ; they do not possess the 

 power of swimming, but are provided with very powerful tarsi and 

 ungues {fig. 7. is. hind-leg of Elmis), whereby they are enabled to 

 retain firm hold on the stones in the most boisterous currents ; thus 

 offering an admirable instance of adaptive creation in the provision 

 made for those insects destined to live in violent running water, 



* BiBLioGR. References to the Elmides. 

 Latreille, in Hist. Nat. des Fourinis, p. 400. 



M'dller, in lUiger Magasin, vol. v. Ditto, in Germar's Magasin, vols. ii. and iv. 

 Diifour, in Ann. Sc. Nat., new series., vol. iii. 

 Audouin and Bridle. Hist, des Ins. Coleopt. vol. ii. 

 Contarini. Sopra il Macronychus. Bassano, 1832. (Ann. Soc. Ent. de France, 



1833, p.xlv.) 

 GuMn. Icon. Regne Animal. 

 And the general works of Stephens, Curtis, Gcrmar (Ins. sp. nov, ), Sec. 



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