156 THE NORTHERN MICROSCOPIST. 
having radial lines. The small ones are free from the radial mark- 
ings, and the integument is semi-transparent. On one-half of the 
pad I have counted 117 of these suckers, so if we double that 
number for the whole of the pad, we shall have close on 250 
suckers, or 500 on both /arsz. The female does not possess this 
piece of apparatus, but has the advantage of size, and has her wing 
cases grooved from the base to the apex, whereas those of the male 
are quite smooth. I have before referred to the pugnacious nature 
of this beetle, ready to wage war at a moment’s notice, and not at 
all particular as to the size of his antagonist. We can with profit 
take a glance at his means of offence and defence. First of all 
we find him possessed of a powerful pair of mandibles or jaws, in 
the use of which he is very dexterous. If you doubt it, go to the 
nearest pond, catch one and handle him. ‘The tarsi end in a pair 
of savage-looking claws, which are no doubt formidable weapons, 
and close by these are the suckers with which to fasten himself to 
his victim, like the suckers on the arms of the Octopus or cuttle- 
fish. Each pair of legs terminates in a pair of sharp claws, and 
underneath the ¢horax, at the setting-on of the large swimming 
paddles, is a peculiar barbed protuberance, with the points set to- 
wards the posterior apex of the beetle, which being forced against 
the hand cause a pricking sensation. This is almost invariably 
felt, as the beetle, when captured, always attempts to back out of 
the hand. Whether he is aware of the use of this weapon, or even 
if he is aware of the possession of it, I cannot say, as it is a fixture, 
and only comes into use when he is walking backwards. He 
possesses another weapon, which is rather more repugnant than 
dangerous. The Dyticidz exude a white fluid of a very unpleasant 
odour when captured. This performance is not peculiar to this 
family, for we find a family of Geodephagous beetles exuding a 
black fluid under similar circumstances. The Dytiscus beetle may 
be kept in an ordinary aquarium, but not in company with fish, 
newts, or anything of that kind. If you make the mistake of 
putting him with your pets once, you will not be likely to repeat 
the experiment. I am informed that fairly large carp are some- 
times killed by them. 
The first sample of Dytiscus marginalis which I remember cap- 
turing was clinging to a fish of about the size of the middle finger, 
which he had evidently killed, and was so intent on his feast, with 
his mandibles inserted, floating tail uppermost for breathing pur- 
poses, that I considered him to be dead, but when I got him and 
his prize into my little landing net didn’t he show fight! Not 
knowing his nature, and thinking that, being brothers in adversity, 
the occupants of my collecting bottle would be all right, I popped 
him in, but soon found that he had made a dreadful havoc amongst 
the tadpoles, heads and tails being mixed together in dire confusion 
