Stenus.l STAPHTLINID^. 327 



STENUS, Latreille. 



This genus comprises upwards of three hundred and fifty species ; of 

 these about one hundred and thirty are found inEurope; the rest are widely 

 distributed over the surface of the globe ; a considerable number occur in 

 North America, and a certain number are found in Central Asia, Ceylon, 

 Japan, Brazil and Chili, Tahiti, the Australian region. Eastern Africa 

 and Madagascar, &c. ; as a rule they prefer wet situations, but some are 

 found in dry sandy or chalky districts ; they fall naturally under two 

 great sections, viz. those that have the penultimate joint of the tarsi simple, 

 and those in which it is bilobed ; the species belonging to the latter 

 section are chiefly attacheil to plants, to which the tarsal lobes apparently 

 enable them to cling ; in all tlie Stent the ligula, paraglossae, and labial 

 palpi are very slightly jointed with the mentum, and at death are some- 

 times protruded at the end of the long gullet, forming a kind of proboscis; 

 this is not the case with Dianous, in which the ligula is said not to be 

 productile, whereas in Stenas it is, though wrongly, said to be productile. 

 There are about sixty British species of Stenus, which may for conve- 

 nience sake be divided into several sections or divisions, depending on the 

 formation of the tarsi, the presence or absence of margins on the hind 

 body, the presence or absence of an orange spot on the elytra, and the 

 relative length of the posterior tarsi ; there are three or four species which 

 have the formation of the penultimate joint of the tarsi intermediate be- 

 tween that of the species forming the two great groups ; after some consider- 

 ation I have placed these in a separate section. 



I. Penultimate joint of tarsi simple, not, or scarcely, broader than third joint ; third 



joint always simple. 

 i. Hind body plainly margined at sides throughout. 



1. Elytra with a round orange or yellow spot on each. (Section I,, p. 327.) 



2. Elytra black, unicolorous. (Section II., p. 330.) 



ii. Hind body not margined at sides (except sometimes the first one or two basal 

 segments). (Section III., p. 342.) 



II. Penultimate joint of tarsi semi-bilobed, not much broader than third joint 

 (Section IV., p. 344.) ^ 



III. Penultimate joint of tarsi very strongly bilobed, evidently broader than third 

 joint. 



i. Hind body plainly margined at sides; elytra black, unicolorous. (Section V . 



p. 346.) 

 ii. Hind body not margined at sides (except sometimes at extreme base). 



1. Elytra with a round orange spot on each. (Section VI., p. 35G.) 



2. Elytra black, unicolorous. (Section VII., p. 356.) 



(Section I.) 



The species belonging to this section are at once distingiushed by the 

 simple penultimate joint of tarsi, the orange spots on the elytra, and the 

 long posterior tarsi which are not much shorter than the tibite; they 

 are found on the margins of ponds and streams, or in damp marshy 

 places. 



