SCIENCE-GOSSir. 



545 



completely formed, and the pupa assumes a strange 

 shape, very unlike that of the larva. At the 

 head end is a great rounded mass which encloses 

 the wings and legs of the fly, besides the month 

 parts and other organs of the head. Each 

 appendage has its own sheath, pari of the proper 



pupa-case. The skin split.- along the back of the 

 thorax, and here the fly emerges, extricating it- 

 legs, wings, head, and abdomen from their closelj - 

 fitting envelope." Drawing from photograph 

 (rig. 0) represents the manner fit' emergence. " The 

 mouth of the female gnal is provided with a case 

 of instruments fur piercing the skin and drawing 

 blood. The foremost of these is a tube split along 

 its hinder side, which lies in front of the rest, and 

 is used in suction. This, though long and slender, 

 is stouter than the delicate parts behind it. 

 and it serves to stiffen and protect them then 

 come fine, long, and slender blades of great 

 delicacy. Two pairs correspond to the mandibles 

 and maxillae of other insects, though here they are 

 so simplified and attenuated that it is not easy 

 to make out the correspondence. The maxillae 

 are furnished near their tips with a row of 



Fin. i. Larva op Gxat. 



pupal skin, and the appendages are cemented 

 together by some substance which is dissolved or 

 softened by alcohol. At the tail end is a pair of 

 flaps which form an eflicient swimming- fan. The 

 body of the pupa, like that of the larva, is abun- 

 dantly supplied with air-tubes, and a communica- 

 tion with the outer air is still maintained, though 



In;. ::. Pupa of Gnat. 



in an entirely different way. The air-tubes no 

 longer open towards the head. Just behind the 

 heart of the future fly is a pair of trumpets, so 

 placed that in a position of rest the margins of the 

 trumpets come flush with the surface of "the water. 

 Floating in this position the pupa remains so long 

 as it is undisturbed : but if attacked bv any of the 



Fks. -i. Female. Fig. a. Male. 



Hkad Parts of Gnat. 



predatory animals which abound in the fresh 

 water it is able to descend by the powerful swim- 

 ming movements of its tail." Then follows an 

 explanation, too long to quote, as to why the 

 respiratory organs are changed from the tail end in 

 the larva to the head end in the pupa. " But a 

 time comes when the fly has to escape from the 



Fig. G. Emergence of Gnat. 



extremely minute saw-teeth. There is also a fifth 

 unpaired implement, which is an extraordinary 

 development of a part of the insect's mouth, which 

 is usually quite inconspicuous. Besides these 

 piercing implements, the gnat is provided with a 

 soft, flexible sheath which represents the labium. 

 This takes the shape of a tube split along its fore 

 side, which surrounds and protects the delicate 

 parts within. The extremity is divided into two 

 lobes.'* — J. J. Wilkinson. 



[Mr. Wilkinson's quotations from Professor Miall 

 need no further explanation. The gnat (Cities 

 pipiens) would make an excellent study for micro- 

 scopical beginners, perhaps even more so than the 

 common cockroach. We may call attention in 

 addition to the beautiful antennae of the male 

 gnat, and to the scales upon the wings and body. 

 which latter can be readily removed by means of a 

 camel-hair brush, and so transferred to a slide. 

 The larva in particular makes a most interesting 

 microscopical object, owing to its transparency. 

 which enables the tracheal tubes, the digestive 

 tube, and contractile vessel that performs the duty 

 of the heart to be readily made out. The gnat 

 ('. jii]>icits must not be confused with the allied 

 ^•enus Chironomvs, or Midges. — En. Microscopv. 

 S.-G.] 



