LABT^ or WATER-PLIES. 267 



magnifying-glass. Under the microscope, the creature will be 

 even more interesting, if possible, than when seen at liberty 

 in the water through the magnifying-glass, though its con- 

 dition will not, of course, be natural. 



The larva has a curious habit of suddenly turning itself, so 

 that its head and tail change places. Sometimes, instead of 

 making only half a turn, it will make the whole turn, so 

 quickly that the eye can scarcely follow it, as if in obedience 

 to the drill-sergeant's command, " As you were ! " In summer 

 these larvae may be taken from ponds of clear water in great 

 numbers. Too many must not be kept in the same vessel : 

 three or four in one which will hold about a quart of 

 water will be quite sufficient. If such a vessel is provided 

 with some healthy aquatic plant, and a quantity of water- 

 fleas and the like, the phantom lai-vae will give no trouble 

 whatever. The Crustacea and their offspring wUl always provide 

 them with plenty of suitable food. These larvae often live 

 for a long time before they become pupae. I have had some 

 for eight months. During that time only a very small pro- 

 portion of those I first captured developed into the perfect 

 Midge. But others which I had taken earlier in the year 

 (about June) entered the imago condition much quicker. 



The pupa of Gorethra plumicornis is somewhat like that of 

 the gnat. The change from the larva to the pupa is very 

 great indeed. Professor Rymer Jones, in reference to this 

 change, says that "the air-sacs, situated both in the thoracic 

 region and in the hinder portion, burst and unfold themselves 

 into an elaborate tracheal system, and a pair of ear-shaped 

 tubes, of which not the slightest trace could hitherto be 

 discerned, make their appearance upon the dorsal aspect of 

 the thorax; two long tracheae seem to be thus simultaneously 

 produced, occupying the two sides of the body, and constituting 

 the main trunks, from which large branches are given ofE 

 to supply — in front the head, the eyes, and the nascent limbs; 

 while posteriorly they spread over the now conspicuous ovaries, 

 and terminate by ramifying largely through the thin lamellae 

 (plates) that constitute the "caudal appendages." The vessels 

 in which the larvae and pupae of Gorethra plumicornis are 



