156 THE ENTOMOLOGIST. 



THE GENERA HYDROCHUS, OCTHEBIUS, and HYDRMNA. 

 By Rev. W. W. Fowler, M.A., F.L.S. 



These genera of the Hydrophilida) are, as a rule, almost 

 entirely neglected by beginners ; and even advanced students of 

 Coleoptera seem often to have very little knowledge about them. 

 They are best obtained by using a net shaped like a prawning-net, 

 with a straight iron edge, with which the damp, mossy, and 

 grassy sides of ponds and watercourses may be thoroughly 

 scraped, and so many things obtained that are lost by using the ordi- 

 nary ring-net. Many of the species, in fact most of the Hydrcence, 

 frequent running brooks and narrow watercourses. These may 

 be captured by placing some thick frayed string across the 

 stream, so that it rests on the surface of the water, and then 

 stirring the stones at the bottom, and tapping and scraping the 

 sides some little way up the stream : the insects will rise to the 

 surface, and, as they invariably cling to the first object they meet 

 with, will almost all be found collected on the string. In swift- 

 running shallow streams, where there are stones and boulders 

 projecting above the surface, or approaching near to the surface, 

 it will be found a very good plan to place the net in the stream, 

 just below a convenient stone, and then gently rub the sides 

 under the water with the fingers. The beetles will then become 

 detached, and be carried down into the net. By employing these 

 methods Dr. Power has captured large quantities of Hydrcence, &c, 

 and has added several new species to the British list. On warm 

 days in summer some species of Octhebii may be found by 

 hundreds floating on the top of the w r ater in stagnant pools, or 

 basking on the mud. The insects belonging to all three genera 

 are excessively sluggish ; and, as some are very minute, it 

 requires great patience to discover them in the net, for they will 

 often remain perfectly motionless until the net is almost dry. 



Of the genus Hydrochus we possess four species, which may 

 easily be distinguished from one another : — 



H. brevis, Herbst, is a short stumpy-looking insect, with the 

 body almost ovate, and in consequence the elytra much broader 

 than the thorax ; it is of a shining black colour, and has very 

 deeply punctured elytra. It is a very marked species, and is 

 probably generally distributed, but is very scarce. Stephens 



