58 THE PREDACEOUS WATER BEETLES, 
Amongst other curious things were some of the beetles I had come to 
seek—a small species, with four light-coloured spots on the elytra, which 
I afterwards made out to be the common Hydroporus palustris. I was, 
however, much pleased with the insect at the time. The same dayI 
caught several specimens of Hyphydrus ovatus, and one of Dyticus 
marginalis, and thought myself well repaid for my trouble. I learned 
one lesson from this first trial, namely, that laurel leaves are of no use 
as a killing agent.* So I obtained some cyanide of potassium, placed it 
in a bottle, and poured over it some plaster of Paris, to keep it in place 
and make a level bottom. 
My next day out, which was in about a week after the first, was 
spent in the same district, but I extended my field of operations. 
Nothing very uncommon was met with this time, excepting Hygrotus 
( Hydroporus ) pictus ; several specimens of Acilius sulcatus also occurred, but 
this species I afterwards found to be common. Inexttried the Charnwood 
Forest district, but soon discovered that if I wanted water-beetles I must 
keep in the valley of the Soar. After this, on every fresh excursion, my 
net brought up some new species. In the Abbey Meadow I first found 
Hydroporus depressus ; from Barkby Brook were captured Hydroporus 
12-punctatus, (duodecimpustulatus,) and Colymbetes (Agabus) maculatus and 
nebulosus—the latter being common in all clear water. Early in Junel 
brought from the Anstey ponds Haliplus obliquus, Laccophilus hyalinus, 
and Colymbetes fuscus; from Thurmaston Sandhole, Hydroporus planus 
and H. memnonius. This last place yielded the rarest species, and, 
excepting the tributaries of the Soar, was the most prolific. It is a large 
extent of land from which ballast has been obtained, and is full of 
bright pools, which, as the summer advanced, became covered with a 
rich growth of conferve. It was here I obtained the single specimen (of 
the season) of Pelobius Hermanni. I tried many times, but never 
succeeded in taking any more Pelobius. 
As the season advanced, I became better acquainted with the 
particular habitats of the various water-beetles, and could almost tell at 
sight, by the appearance of the water, what species were likely to occur. 
I seldom found anything in black muddy ponds except Colymbetes 
(Agabus) Sturmi and bipustulatus, and noticed that all the brightly 
coloured and spotted beetles were found in running or clear water; thus 
Thad C. (A.) vitreus (didymus) from Barkby Brook, and C. (A.) maculatus 
from a brook near Syston. I scarcely ever found many beetles in ponds 
where Lemna trisulca grew, but in those covered with ZL. minor I was 
generally very successful. In streams by which nanthe grew, bright 
beetles were plentiful. I do not know in what relation these plants 
stand to water-beetles; it might be only an accidental circumstance, but 
I always regarded these characteristics as signs. I never found 
Laccophilus hyalinus with L. minutus. The latter, which is the brighter 
* Mr. Robson must have been unfortunate in the laurel he used: or, perhaps, he 
did not keep it dry. Good laurel, properly used, is certainly the best “ killing agent’’ 
for Coleoptera, and it is tobe hoped that Mr. Robson will try again. Cyanide of 
potassium is bad in many ways, but principally because it renders the beetles stiff 
aud hard to set.—Ebs. M.N. 
