Sialis larvae occur in most ponds with muddy bottoms. They may be taken by scooping up some of the mud in a long-handled spoon--a most useful instrument for the collector--and washing it, or by throwing in the drag, and bringing to land a mass of water-weed, roots and all. A few may generally be detected near the roots. They may be picked up with a small pair of forceps, or with a brush, and dropped into a bottle; or, better still, into separate tubes; for they are fierce and voracious, and, failing other food, by no means indisposed to prey on each other. Their general appearance, and especially their powerful mandibles, give them some resemblance to the larvae of a water beetle, for which a celebrated naturalist not unnaturally took them, when he began to study them. And this would seem to be the opinion of some mounters, for I have a slide of the mouth parts of this larvae, labelled ‘Mouth parts of the larvae of a water beetle.’ It was not till I had broken up a good many Sialis larvae that I found out what the slide really was. These larvae may be kept alive in small bottles of water, if they are supplied with food. They will eat Chironomus larvae and those of Tanypus. Professor Miall has found that they will eat caddis-worms and May-fly larvae. Probably, no small aquatic creatures that they can overcome are safe from them. A larva that is full-fed, and ready to change to become a pupa, will measure about an inch in length or a little more (Fig. 85). The general colour is brownish, with dark markings. The legs are powerful, and our lens will show us that they end in two strong curved claws. From each of the first seven segments of the abdomen are given off a pair of jointed tracheal gills or breathing-organs, which are directed upwards and backwards when the larva is at rest--a rare occurrence--but which wave to and fro in the water when the creature is swimming. From this fact has arisen the statement found in most books that the larva uses these gills not only for respiration, but for locomotion. Professor Miall has come to a contrary conclusion, and, as he has kindly informed me, is confirmed in his opinion by the weakness of the muscles. [Illustration: FIG. 85.--Larva of Sialis (enlarged).] It will be well to make repeated observations till we are satisfied on the subject. When these larvae are kept, the conditions necessary to provide them with food and to keep the water aërated by means of growing vegetation are unfavourable to close observation. It will, therefore, be necessary to remove one or more of these larvae to a bottle in which there is nothing but pure water.