46 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I39 



complete narrow annulus (IXT, IXS) as in the adult male (fig. 27 B), 

 and below the small tenth segment projects a pair of large lobes (fig. 

 16 E, PhL) on a common base arising from the sternal arc of the ninth 

 segment (F). These lobes are the genital appendages of the male as 

 far as they are developed in the pupa. Male and female pupae, there- 

 fore, can be distinguished by the presence (A) or absence (B) of the 

 genital lobes {PhL), though in the male the lobes might be mistaken 

 for the tenth segment, since the latter is mostly concealed above them 

 (A, X). 



THE PUPAL METAMORPHOSIS 



The pupal life of most mosquitoes is very short, two or three days 

 or less, though with some species it is much longer. During this time 

 the contour of the adult is modeled by new growth of the epidermis 

 beneath the pupal cuticle, while the mouth parts, wings, halteres, and 

 legs take on the adult structure within their pupal sheaths. At the 

 same time reconstruction of internal organs takes place inside the 

 body. The degree of reconstruction necessary to change the larval 

 organs into those of the adult, however, is much less in the mosquito 

 than in many other insects, especially in the higher Diptera. 



The mosquito pupa breaks with the tradition that a pupa is a "rest- 

 ing stage" in the life of the insect. When an ordinary pupa is broken 

 open it is seen to be full of a creamy mass of soft material resulting 

 from the disintegration of the larval tissues. The inside of a mosquito 

 pupa is as clean as that of the larva or the adult, and its organs appear 

 to be intact. Whatever reorganization is going on takes place mostly 

 inside the alimentary canal and the refuse is not thrown into the body 

 cavity. 



The abdominal muscles are so well preserved that the pupa is an 

 extremely active stage of the mosquito, and the thoracic muscles are 

 so well developed that the pupa might be expected to fly if its wings 

 were more mature. As already noted, Hulst (1906) has described the 

 process of muscle histolysis and histogenesis as beginning in the larva, 

 but he is not explicit as to what larval muscles are destroyed or when 

 the imaginal musculature is completed. In Culex, according to Hurst 

 (1890), the muscles of the pupa are those of the imago; the principal 

 muscles are present in the young pupa, but they increase greatly in 

 size. A casual examination of the abdominal musculature in the larva, 

 pupa, and adult shows little difference between the stages, except for 

 the greater size of imaginal muscles. However, we need a more de- 

 tailed comparative study of the muscle pattern and more information 

 on the replacement of individual muscles. 



