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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 139 



wise the young of all winged insects have wing rudiments developing 

 either externally or internally. The unusual thing about the mosquito 

 and related Diptera is that the legs, wings, and pupal respiratory 

 trumpets are fully extruded beneath the cuticle of the thorax at the 

 third larval moult instead of at the moult to the pupa (fig. 9 C). The 

 wings are still in the form of pads (W 2 , W 3 ), but the legs (E) are 

 already fully segmented appendages. 



At a somewhat later period of the fourth instar, the larval cuticle 

 is separated from the abdomen except at the posterior end (fig. 14), 

 and beneath the cuticle on the back of the first segment are now seen 

 the two small suspensory brushes of hairs characteristic of the pupal 

 abdomen. The thorax and the abdomen inside the moulted larval 



Fig. 14. — Fourth-instar larva of Aedes aegypti with larval cuticle (ICt) 

 moulted over the thorax and most of the abdomen. The inner cuticle (pCt) 

 is that of the pupa. 



cuticle, therefore, pertain to the future pupa. The head cuticle of the 

 larva has not yet been moulted, so that the larva in the fourth instar 

 still feeds with its own mouth parts. It breathes with its posterior 

 respiratory apparatus, and uses for locomotion the muscles now in the 

 pupal abdomen. 



The condition found in the mosquito is simpler than that described 

 by Hinton (1958b) in Simulium. Here the fully formed pupa still 

 within the larval skin is active for several days before ecdysis. Its 

 activity is due to the fact that many of the former larval muscles, in- 

 cluding those of the head, remain attached by tonofibrillae to the 

 moulted cuticle of the larva. The pupa of Simulium is thus able to 

 use the larval organs, and it not only continues to feed, but spins its 

 own cocoon. In the mosquito there is no evidence of muscles retain- 

 ing their attachment on the moulted larval cuticle; the insect feeds 

 with the larval mouth parts until the latter are cast off at the final 

 pupal moult. 



The larval musculature of the thorax and abdomen is said by 

 Thompson (1905) in Anopheles to go over into the pupa and the 



