334 Fiftieth Eeport on the State Museum 



pendages, an enlarged thoracic region, and a long ten-jointed abdomen, 

 slightly tapering, with each segment bearing bundles of hairs. J'rom the 

 ■eighth abdominal segment a long tubular organ is given out, ending in 

 a star-like structure bearing a number of cilins. This is its organ of res- 

 piration — all the air that it receives being supplied to the tracheal vessels 

 only through this opening. The terminal joint of the abdomen bears 

 five conical plates which are used in its locomotion. 



The Pupal Mosquito. 



After several moltings, while they rapidly increase in size, the larvae 

 enter upon their third stage of existence, in assuming the pupal stage. 

 At this time they present an uncouth aspect. Their thoracic region has 

 become greatly enlarged, and in front of it are grouped, in separate cases, 

 the legs, wings, mouth-parts and antennae. They still continue in an 

 active state, unlike the quiescent pupal condition of many insects, 

 and even many other Diptera — but they are incapable of feeding. A 

 striking and interesting change has taken place in their breathing 

 apparatus. They suspend themselves from the surface of the water, as 

 before, for respiration, but the air is now taken in through two horn- 

 shaped organs proceeding from the upper part of the thorax. Before, 

 they hung head downward; now, as they have made a material advance 

 in development, more fittingly, head upward. 



In about two weeks, usually, from the deposit of the eggs, the pupal 

 stage is completed, and the insect is prepared to enter upon its final state, 

 a perfect, winged insect. With so brief a period required for its develop- 

 ment, you will perceive that there is ample time for several generations of 

 the insect during the spring and summer months. 



The Final Development. 

 The pupa having fully matured, it rises to the surface of the water 

 where it floats with its thorax elevated above the surface. Exposure to 

 the air dries the exposed portion, and, aided by movements within, it 

 splits along the middle line, and the head and thorax of the inclosed in- 

 sect are thrust out. Slowly the wings, legs, other organs and abdomen 

 are drawn forth through alternating muscular extension and contraction — 

 all the while balancing itself in an upright position with the utmost care, 

 for the problem of how to maintain the center of gravity when elevated 

 so high above its frail and unstable base must necessarily be an exceed- 

 ingly difficult one — it would seem to be an impossibility. The slightest 



