The following description of this larva is principally condensed from De Geer, whence the figures are also taken. The body is long and cylindrical, and divided into eleven segments, of which the first and largest is sub-triangular. The second and third segments are shorter than the rest. The head (_t_) is very small and completely retractile within the first segment, the anterior margin of which completely closes the orifice, so that, in this condition, the creature appears to be headless. The body is covered with spines, some simple and others branched. On the first three segments there are only simple spines; but from the fourth to the tenth segment inclusive there are also on each segment two forked spines--that is, fourteen in all. On the last segment the spines are simple, and here are also four chitinous hooks, one pair much larger than the other. These simple spines carry a white vessel, which extends throughout their whole length; but in the forked spines there are two such vessels placed side by side in the stem, and diverging one to each branch. He comes to the conclusion that these spines are probably the breathing apparatus of the larva, for they are similar to those which he observed in an aquatic caterpillar. Walker[62] calls these spines ‘long filamentous processes, which appear to be internally supplied with air-tubes,’ but he does not seem to have taken the trouble to break up a specimen, or he would have been in no doubt as to their real nature. This is shown by the fact that the larva never comes to the surface to take in a supply of air, but contents itself with the oxygen dissolved in the water. [Illustration: FIG. 79.--Forked spine of Limnobia, enlarged; the dark lines show air-tubes.] The pupa is quite as remarkable as the larva, though the breathing apparatus does not assume the form of spines, but consists of two ‘trumpets,’ one on each side of the head, as is the case with the pupae of gnats, using that term in a wide sense. The colour is a greenish-brown, dotted with black. The abdomen is capable of a good deal of motion from side to side; and by this means the pupa can raise itself to the surface of the water to take in a supply of air. De Geer remarked that when the pupa rose for this purpose it lay with its body horizontal, having the lips of the trumpets a little above the surface. It appeared not to like being placed on its back, because in that position the trumpets cannot be raised above the surface. When he tried the experiment of putting the pupa back downwards, it wriggled over by bending the abdomen. [Illustration: FIG. 80.--Pupa case of Limnobia. (From a photograph taken at the Yorkshire College, Leeds.)]