The Naturalist on the Thames | Page 9

Kent. The bladderworts fade instantly, and are not
much interfered with, and though the fritillaries are picked for market,
the roots are not dug up because that would injure the meadow turf in
which they grow, and business objections would be raised.

INSECTS OF THE THAMES
Except among the select few, generally either enthusiastic boys or
London mechanics of an inquiring mind, who keep fresh-water
aquariums and replenish them from ponds and brooks at "weekends,"
few persons outside the fancy either see or know much of the water
insects,[1] or are aware, when floating on a summer day under the
willows in a Thames backwater, of the near presence of thousands of
aquatic creatures, swift, carnivorous, and pursuing, or feeding greedily
on the plants in the water garden that floats below the boat, or weaving
nests, tending eggs, or undergoing the most astonishing transitions of
form and activity, on or below the surface. Many of them are perhaps
better equipped for encountering all the chances of existence than any
other creatures. They can swim, dive, and run below water, live on dry
land, or fly in the air, and many are so hardy as to be almost proof
against any degree of cold. The great carnivorous water-beetle, the
dytiscus, after catching and eating other creatures all day, with
two-minute intervals to come up, poke the tips of its wings out of the
water and jam some air against its spiracles, before descending once
more to its subaqueous hunting-grounds, will rise by night from the
surface of the Thames, lift again those horny wing-cases, unfold a
broad and beautiful pair of gauzy wings, and whirl off on a visit of love
and adventure to some distant pond, on to which it descends like a
bullet from the air above. When people are sitting in a greenhouse at
night with no lamp lighted, talking or smoking, they sometimes hear a
smash as if a pebble had been dropped on the glass from above. It is a
dytiscus beetle, whose compound eyes have mistaken the shine of the
glass in the moonlight for the gleam of a pond. At night some of the
whirligig beetles, the shiny, bean-like creatures seen whirling in
incessant circles in corners by the bank, make a quite audible and
almost musical sound upon the water. The activity of many of the water
insects is astonishing. Besides keeping in almost incessant motion,
those which spend most of their time below water have generally to
come up constantly to breathe. Such are the water-bugs,
water-scorpions and stick insects, which, though slender as rushes, and
with limbs like hairs, can catch and kill the fry of the smaller fishes.
Most of these are like divers, who have to provide themselves with air

to breathe, and work at double speed in addition.
If a group of whirligig beetles is disturbed, the whole party will dive
like dabchicks, rising to the surface again when they feel the need for
breathing-air again. The diving-bell spiders, which do not often
frequent the main Thames stream, though they are commonly found in
the ditches near it, gather air to use just as a soldier might draw water
and dispose it about his person in water-bottles. They do this in two
ways, one of which is characteristic of many of the creatures which live
both in and out of the water as the spider does. The tail of the spider is
covered with black, velvety hair. Putting its tail out of the water, it
collects much air in the interstices of the velvet. It then descends, when
all this air, drawn down beneath the surface, collects into a single
bubble, covering its tail and breathing holes like a coat of quicksilver.
This supply the spider uses up when at work below, until it dwindles to
a single speck, when it once more ascends and collects a fresh store.
The writer has seen one of these spiders spin so many webs across the
stems of water plants in a limited space that not only the small
water-shrimps and larvae, but even a young fish were entangled. The
other and more artistic means of gathering air employed by the spider is
to catch a bubble on the surface and swim down below with it. The
bubble is then let go into a bell woven under some plant, into which
many other bubbles have been drawn. In this diving-bell the eggs are
laid and the young hatched, under the constant watch of the old spider.
Few people care to take the trouble to gaze for any time into a shallow,
still piece of water, in which the bottom is plainly discernible, and a
crop of water-weeds makes a wall on either side of some central "well."
If they do find some such