Himirorerus.'] HYDUOrniMD.i:. 243 



are found, in company with the perfect insects, in the autumn ; they are anophiri- 

 form or louse-shaped, measurinf^ when full fjrown ahout 5 umi. in !i'nf,'th,and 1 mm. 

 in breadth; they arc of a uniform black colour, and luivo the ajx'X of each abdominal 

 segment fringed witli very short hairs; the-ir food is probably niucor, and they prefer 

 rough shiny stones ; when full grown, they leave the water, and construct, upon the 

 edges of the stone, a small cell, by agglutinating together small particles of mud. 

 These cells are sometimes very numerous, giving the fragment of stone a curious 

 appearance : the pupa is of an orange colour, and the imago, when hatched, gnaws 

 its way through its prison, ilulsant (Palpicornes, Plate, Fig. 4) gives the figure of a 

 larva that he hidieves to he that of IT. granulatus : the head and thoracic segments 

 are very broad, and the abdominal segments arc gradually narrowed to the ninth 

 which bears two moderately loug, setose cerci, which serve as organs of respiration 

 (1. c. p. 53). 



H. exsculptus, Germ. Colour variable, some examples being of a 

 dull black, others shining bronze, while occasionally specimens are met 

 with in which either the thorax or elytra, or the base of both, are of a 

 l)right metallic blue colour ; head coarsely punctured in female, more 

 diffusely in male, eyes rather prominent, antennre reddish, club dark ; 

 thorax somewhat cordiform, strongly contracted behind, broadly dilated 

 and flattened in front at sides, with a strong central furrow and two 

 impressions on each side, one round, the other oblique ; elytra short 

 oval, considerably broader than thorax, with strongly punctured, crenate 

 striaj ; legs reddish testaceous, joints usually darker ; in the male the 

 thorax is very convex, rather finely and difi'usely punctured ; the anterior 

 impression is almost obsolete, and the posterior is reduced to a slender 

 line ; in the female the thorax is flatter, and both impressions are very 

 large and deep. L. 1| mm. 



Local and not common in England ; North Wales ; Church Stretton ; Eggington, 

 near Burton-on-Trcnt (very rarely) ; Ilalilax ; Xorthumberland ; Scotland, common, 

 Tweed, Forth, Solway, Clyde, and Moray districts. 



OCTHEBIUS, Leach. 



This genus comprises about fifty species, which are widely distributed 

 ov(;r the surface of the globe from the north of North Amejica to South 

 Africa ; the greater part, howcA'er, occur in the northern and temperate 

 regions of the world ; they are found in both stagnant and )'unning 

 water ; some species are conflned to brackish ponds and ilitchcs, and 

 according to ^I. Bedel some occur exclusively in muddy cavities in rocks 

 which are covered by the sea at high tides : the chief points of distinc- 

 tion between the species are found in the sculpture of the disc of 

 tliorax, the membranous border or posterior angles of the tiiorax (which 

 latter are often excised and filled with membrane), and tlie si-ulpture of 

 the elytra ; the sculpture of the disc of thorax is cliiefly of two kinds, 

 and consists either of a central furrow with a tiansverse line above and 

 below it (like an H l'^'^^ ^*i^ "^i"' •'^ide), the untlci line lieing more or less 

 curved, and secondly of a c(Mitral furrow with two impressions on each 

 side, the front ones circular, and the posterior ones oblitpie and con- 

 verging towartls the base of the central furrow, presenting the appearance 



R 2 



