books on comparative anatomy say nothing
particular has been seen upon their feet except
numerous hairs on one of the sides of these
organs. The eyes of these skating spiders are
arranged two and two in pairs so closely
together that each pair seems only one; but the
pairs are comparatively wide apart. M. Dugés
says of the adult Hydrachna cruenta, that prior
to casting its skin, it makes a hole for itself
with its mouth in the leaves of aquatic plants;
and M. Siebold, having seen it fix itself by the
mouth to the slippery sides of bottles with a
sort of cement, declares that several kinds of
water-ticks, glue themselves to fresh-water algæ
whilst waiting in this position for their moulting.

These skating-ticks, in their growth from the
egg to the spider, undergo metamorphoses: and
thereby hangs a tale. There abound, in ponds
and rivers, beetles with hind-legs like tiny
feathery oars, called Hydrophilidæ, and Dytiscides,
and other Greek names, describing them
as fond of marshes, water, diving, swimming,
capsizing, swirling, or, in fact, all sorts of
aquatic antics. Their forms vary from long
oval to almost globular. The Hydrophilidæ,
having their fore and hind legs both capable of
oaring them, swim by using one leg after the
other, and in their perfect form at least are
herbivorous, whilst the carnivorous Dytiscides
swim swiftly with both legs at once to seize the
animals they devour. De Greer fed Cybister
ræselii with flies and spiders, and had seen one
of them eat a leech. They have even attacked
small fishes. After sunset, and during the
night, these beetles sometimes migrate from
one pond to another, some crawling, but most
of them flying with a noise like that made by
the may-bug. Like fish, they have within them
little bladders, which they can fill with air to
raise themselves from the bottom to the surface
of the water. There are, it is said, four hundred
known species of them. The Hydrophilidæ and
Dytiscides both have dull colours, black or
dark brown, with occasionally bronze-like hues
of grey or green. Many species can imprison
air with their feelers and hairs (antennæ and
cilia), and carry it beneath the water with them.
When the marshes dry many of them plunge
into the mud, or bury themselves beneath
stones, waiting for wet weather. And they can
endure drought a long time. M. Mulsant,
forgetting to renew the water of a bottle in which
he kept a Hydrophilus caraboides for three
months, found it half-buried in mud which had
become quite dry, and saw it, an instant after
being supplied with water, become as lively and
active as before.

I may seem to have been forgetting the
red skaters upon the surface of the streams
all this time. But I have not, for wherever
the Hydrophilidæ and Dytiscides go the
Hydrachna go with them; the larves of these
metamorphosing spiders living parasitically
upon the beetles. These larves have a beak
so long and large that it might easily be
mistaken for a head separated from the trunk.
With their beaks they pierce the body of different
kinds of insects, until their gorged bodies
become as monstrously disproportioned as their
beaks were, when they issued as embryos from
their eggs. They have six feet. For many
years they were classified by the savans as a
genus of themselves, the Achlysia. The red
Achlysia, with formidable beaks and monstrous
abdomens, were found upon the backs of
Dytiscus and Hydrophilus, and erected into a
genus, until an observer saw one moult and
become an eight-legged spider, the well known red-
skater of the quiet pools.

But what are his skates? The microscope
shows nothing but tiny hairs upon his feet. No
naturalist I wot of has answered, or for that
matter asked, this question, and I am therefore
left to my own conjectures. The surface
globules of a pool, being most heated, rarified,
and expanded by the sun's rays, must be the
lightest and largest, and the layers or strata of
globules just below the surface film must
consist of smaller, heavier, and colder globules.
Here, then, is my guess. The red-skater-ticks,
I fancy, entangle a sufficient number of the
relatively large and light globules in their feet-
bristles to bear their weight, and then borne on
aërial skates, scud, dart, and whirl about at
will. The black half-wings (Hydrometra)
probably run upon the waters in a similar way.
The Hydrachna cruenta, or blood-spider, if most
striking when seen upon the pools, is not so
beautiful under inspection as the map water-
tick, a globular spider (Hydrachna geographica),
whose markings are map-like, and whose colour
is polished black with red spots.

The wolf-pirate and the wolf-fisher (Lycosa
piratica and Licosa piscatoria), are also skaters.
Having merely translated them, I am innocent,
I may remark by the way, of giving the spiders
these shocking names, and half suspect the
savans who invented them hoped when they
did it that the spider-wolves would never resent
them, being ignorant of the dead languages.
Among the fox or crafty spiders (Dolomedes)
occur the crafty fringes (D. frimbriatas) spiders
which find the fens of Cambridgeshire very
much to their liking. No naturalist seems to
have observed the feet (tarsi) of the semi-
aquatic insects and Aranedea, to ascertain if
there is any peculiarity of formation common to
all the skaters which enables them to perform
their feats. " Several of the semi-aquatic
species," says Mr. Blackwell, " belonging to the
genera Lycosa and Dolomedes run fearlessly on
the suface of water, and even descend spontaneously
beneath it, the time during which they
can respire when immersed depending upon the
supply of air confined by the circumambient
liquid among the hairs with which they are
clothed."

Readers into whose hands books like
Blackwell's History of the Spiders of Great Britain
and Ireland rarely fall, may feel curious to see a
specimen of the sort of description of a spider
which the present state of scientific opinion
approves and requires; and I feel tempted to
extract his description of the wolf-pirate to