1

Fig. 26.

arranges them in a transverse and oblique direction,
so as to form quite bulky masses. Another com-
mon species (L. flavicornis) is not
at all particular as to what materials
it uses in forming its cases, as the
following sketches will show. Shells
are employed very abundantly, and
most of the caddis-worm cases to be met with in

any ditch or tarn, are the work of this particular
species. Indeed, the flavicornis seems to be ex-
ceedingly capricious in its selection of building
materials. At one time it will choose only seeds, at

another only shells or grains of sand. The shells are often fastened together even when their inmates are yet alive, and the latter have to put up with this forcible captivity till such time as the larva shall be transferred to its next or winged stage of existence, and the cementing material binding the elements of its former case together, shall be dissolved away. Another common form of caddis-worm case is

Fig. 33.

Case of Limnephilus lunatus.

Fig. 34.

Case of Anabolia nervosa.

made by an allied species, L. lunatus, which, like the species of an allied genus, Anabolia nervosa, makes its tube of fine sand, or the equally fine fragments of fresh-water shells. In both these species, the case has attached to it small twigs or other pieces of wood, as balancers. These twigs often extend far beyond one end of the tube. In hunting for these "small deer," it is more than probable you may come across another species of caddis-worm called

Fig. 35.

Case of Limnephilus pellucidus.

In

Limnephilus pellucidus (Fig. 35), whose case is formed of entire leaves, or large pieces usually of willow or poplar. Sometimes, it is composed of pieces cut out from the stems of bulrushes, &c., and flatly laid over each other, so as to form broadish masses. the interior of these is the slender tube containing the larva. The leaves, &c., form a capital protection, and you have to pull the pieces quite from each other before you can fully decide that they were formed as worm-tubes. We have also caddis-cases of yet other species, with straight or curved tubes, sometimes gradually tapering to one end. Such are the cases of Sericostoma, Setodes, &c. They are formed of sand, or very small stones, neatly cemented together. Some species of Setodes make delicate little tubes, entirely formed of silky secretion, without any admixture of extraneous objects. Not uncommon in ditches and tarns, is the caddis-tube of the Molanna angustata (Fig. 38). It will be met with most abundantly in ponds having a sandy bottom. The tube is long, broad, and rather flattened, and is composed of fine sand grains cemented together. The upper surface, at the front end, projects over the larva, so that it

Fig. 36.

Case of Sericostoma.

Fig. 37.

Case of Setodes.

Fig. 38.

forms an ingenious covering whenever the larva is forced to protrude its head in search of food. These larvæ generally live on vegetable matters, although they have been said to be not indifferent to the ova of fishes, &c. The mechanism of the tubes of caddisworms is, geologically speaking, very ancient; for similar cases are found in such abundance in the Miocene strata of Central France, that actual rocks are composed almost wholly of their remains.

Cases of Molanna angustata.

The larvæ of the Ephemera and Water-beetle (Dytiscus) inhabit the same water, as many small fishes find out to their cost, for these creatures are as ferocious, after their kind, as the greater land carnivora. The latter feeds on tadpoles, and keeps down the tendency to swarm of these reptilian progeny. The Dytiscus is especially fierce, and, when kept in an aquarium, will not hesitate to attack the stick that is pointed near it. One grip is generally sufficient to settle a poor tadpole, as the jaws actually meet through its sides. To the microscopist the breathing tubes (trachex) of this insect are very interesting. The best way to obtain them is to make a careful incision along the centre of the back with a pair of fine scissors. After a prolonged soaking in acetic acid, and repeated washing, the skin may be removed almost entire.

The tracheal or breathing system of the Ephemera must be served in the same way, to obtain it as a microscopical specimen. It is, however, much more difficult to manipulate, on account of the fragility of the leaflets.

Space only allows brief reference to the surface insects, the well-known Whirligig Beetles (Gyrinus

natator), to be seen going through their fantastic quadrilles on the surface of every stagnant pool. But these humble creatures have a fair geological antiquity; for the Forest bed, cropping up from beneath the glacial deposits of the Norfolk coasts, shows that this same species was in existence long before England became an island for the second time,