726 Marvels of the Universe 
But it is not our pur- 
pose in this present writing 
to attempt to deal with 
Bugs generally. We _ pro- 
pose to take as examples a 
few that are addicted to 
an aquatic life and which 
may be studied in any 
pond. Several of these are 
known to country boys, 
not as Water Bugs, but as 
Ditch-skaters. They have 
Seto Wee an EES: long, thin, spider-like legs, Photo by] [H. Main, F.E.S. 
EER SCOREION: which are probably the THE BOATMAN. 
The nymph or pupal condition, in 
S ss a - Empty pupal skin from which the 
which only rudimentary wings are evident. natural prototypes from fully developed Boatman has emerged. 
(Twice the natural size.) which man has evolved (Twice the natural size.) 
the idea of ski and snow-shoe. The principle is, at least, the same: that if a sinkable weight 
is distributed widely over a fluid or other yielding surface, it will not sink. Look at these 
Ditch-skaters moving nimbly over the surface of the pond, and you would imagine that they are 
unsinkable. So active are they that if you wish to carry away anything more than a generalized 
idea of their forms and structure you must catch a few and examine them at close range. I say a 
few, because a single specimen would be very misleading, as you might therefrom get the notion 
that they are all alike. There are really a number of distinct species, so distinct in some cases that 
they represent different genera, though at a glance most of them are alike; but it will be found 
no easy matter to capture an individual, so quick are they to elude hand or net, doubling on 
their tracks with astonishing facility. 
One of the most plentiful of these Ditch-skaters is Gerris, whose dull, almost black back is 
margined with a thin reddish line. Its length is only a third of an inch. One would hardly suspect 
it of having wings, but there are four of them, neatly packed and lying close to the back. The 
underside is clothed with short, silvery-grey hairs. There is a peculiarity about the legs. In most 
insects the bases of these all come close together along the centre of the underside. In Gerris the 
first pair are only just behind the head, whilst the second and third pairs appear to be attached half- 
way through the 
insect’s length, but 
the appearance is 
really due to the 
first joint being 
closely pressed to 
the body; and 
instead of having 
their attachment 
in the middle line 
we they arise from the 
. « 
sides of the body. mf. 
Photo by] [H. Main, PBL. This arrangement ~ 
Photo by] [W. B. Johnson. 
THE BOATMAN. has its importance 
THE BOATMAN. 
The stout body slopes from the sides to a in connection with 
ridge along the back. As the Boatman swims on This Water Bug swims on his back, and uses 
the peculiar habits the long third pair of legs after the manner of 
(Slightly reduced.) 
his back this ridge becomes a steadying keel. 
(Twice the natural size.) of the insect, and sculls. 
5) 
