200 SHARP: HYDRADEPHAGA OF LANCASHIRE AND CHESHIRE. 
the thorax which renders them conspicuous. Three of these are 
taken in the district. One of them, D. assimilis, seems to have 
been identified first as British, by Dr. Schaum, from specimens 
taken by Mr. Gregson, in Mosslake Fields, Liverpool. I have found 
it commonly over all the district that I have explored. Of another 
species, D. 12-pustulatus, Mr. Stott, of Bolton, has an interesting 
observation. He found a number of them hybernating under water; 
under the bark of rotten sticks, in a pond at Lostock, in January 
1886. This is the only instance that I have ever come across of any 
number of the Hydradephaga being found zz hybernaculo. The case 
demonstrates to us very forcibly how completely vital action must be 
suspended during hybernating, because respiration must cease almost 
entirely. For the Wydradephaga do not, like fishes and gill-bearing 
larvee, breathe the air held in solution by the water; they are compelled 
to fill the space between the elytra and the abdomen with atmospheric 
air obtained from the surface of the .water, and if kept in a lightly 
stopped bottle full of water to the exclusion of any air, they will, as 
a usual thing, very soon drown; therefore, it seems that we must 
conclude that these hybernating beetles found under bark of sub- 
merged sticks, existed for probably several months on the minute 
bubble of air retained under their elytra from their last visit to the 
surface. This species, however, I have not taken so frequently as 
either D. assimilis or D. depressus. The other two, D. /atus and 
D. griseo-striatus, do not occur here. The first inhabits clear running 
streams, and the last is quite a northern insect. 
We now come to /ydroporus (wayfarer of the water), the largest 
of the genera of the Hydradephaga. The species are all small 
obscurely coloured insects, and they present to the student the 
greatest difficulties in the way of identification. Canon Fowler 
enumerates thirty-six species ; a great many of them are uniformly 
lack, and these are the most difficult of all. One of them, 7. palustris, 
is the most abundant water-beetle we have in this district, except 
perhaps Hadiplus rujficollis ; but of the thirty-six species there are 
records of twenty-two or twenty-three. 
One 1. ferrugineus, a very rare species, is cited as from Whalley 
near Preston, by Fowler, but no authority is given. 
Two species rest on single specimens. Dr. Ellis took A. celatus at 
Otterspool, on the Mersey shore, and I have taken one specimen of 
ff, flavipes at Ledsham, Cheshire. 
At Simonswood, Lancashire, Dr. Ellis took A ¢vistis and H. 
melanarius, and in the same place I took ZH. a¢viceps, and in Delamere 
two specimens of H. obscurus. These are our only records of these 
species. 
Naturalist 
