262 THE ENTOMOLOGIST. 



are attached by one end to a central spot at the end of the 

 leg, where they stand with their shorter convex edges next 

 to the foot, the teeth being directed outwards ; and together 

 they form a radiate tuft which can be retracted by the 

 muscular axis of the proleg. I know that these prolegs have 

 been termed "air-tulaes," and "respiratory organs;" even 

 the anterior pair are called "air-tubes" by Burmeister; but, 

 without considering their structure, the way in which they are 

 used as organs of prehension and locomotion ought, I think, 

 to convince any observer that they are really prolegs. 

 Besides, this larva keeps always under water, never coming 

 to the surface for air; consequently, air-tubes would be 

 useless. There are four egg-shaped appendages at the 

 extremity of the abdomen, the upper two of which are larger 

 than the others. There are only three in Reaumur's figure, 

 and these are equal and cylindric. Near each end of the 

 penultimate segment are two fleshy indistinctly jointed worm- 

 like filaments, — these are not well represented by Reaumur. 



The larva has four eyes, two on each side of the head; two 

 strong, toothed mandibles, with other oral organs, and, no 

 doubt, a spinning apparatus; for it collects any small pieces 

 of dirt which come in its way, and fastens them together by 

 threads, and so makes an irregular tube, in which, holding 

 by its prolegs, it waves its body up and down, thus producing 

 a current which brings it food, and at the same time a fresh 

 supply of water to its branchiaB. Sometimes it will come out, 

 when, holding by its anal prolegs to any slight web it may 

 have made, it will search for food, its jaws working incessantly 

 and its head moving up and down, while it twists itself about 

 in all directions with restless activity. Occasionally it will 

 remain comparatively quiet, resting on its anterior prolegs, 

 then reminding one of a pig with its feet in the trough, 

 groping for a bonne bouche. It generally remains concealed, 

 and only when distinbed, or when seeking a fresh resting- 

 place, is it seen swimming about with that peculiar writhing 

 motion which everybody has observed. There are a few 

 scattered hairs about the head and thoracic segments, and two 

 scanty tufts on a protuberance on the top of the anal segment. 



The pupa of this insect also has been incorrectly represented. 

 In the figures that are copied from Reaunnn- the abdomen 

 has a segment more than it should have ; the branchial tufts 

 on the thorax are too symmetrical, and the hairs too scanty; 

 the wing-cases are not of the right shape, and the tubes 

 wiiich contain the legs of the coming gnat are not shown. 



