38 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I39 



ing organs, and respiratory apparatus that are essential to the life of 

 the larva. 



The corpora allata of the mosquito larva are described by Boden- 

 stein (1945) as a "corpus allatum complex" composed of two small 

 cellular bodies of elongate form, tapering posteriorly, attached laterally 

 on the aorta just behind or within the neck. Anteriorly they adhere 

 closely to a transverse trachea and are connected with each other by 

 a loose chain of cells. Each body is entered by a slender nerve from 

 the brain. Since the bodies contain different kinds of cells it is possible 

 that they include elements of the usually separate corpora cardiaca. In 

 higher Diptera the aorta is surrounded by a cellular ring, which is 

 thought to include the corpora allata and corpora cardiaca, but accord- 

 ing to Bodenstein the nature of the cells in the mosquito larva is not 

 certain. The larval complex goes over into the adult in reduced form 

 as two small, rounded bodies lying on the sides of the aorta. 



If the fourth-instar larval mosquito behaves as other larvae have 

 been shown to do when experimentally given an extra dose of juvenile 

 hormone, it should go over into a fifth larval instar. In this case the 

 larva issuing from the fourth-instar cuticle would have external legs 

 and wings ! We can only wait the results of some endocrinologist who 

 may make the experiment. 



When at last the cuticle of the larval head is moulted, taking with 

 it the larval antennae and mouth parts, the corresponding pupal organs 

 are rapidly developed within the still-unshed larval cuticle. The recon- 

 struction of the mouth parts involves an extreme change from the 

 specialized organs of the larva to the equally but differently specialized 

 organs of the adult. The development of the pupal mouth parts has 

 been described by Thompson (1905) for Culex, and by Imms (1908) 

 for Anopheles. 



The pupal labrum begins its growth as a fold of the epidermis at 

 the anterior end of the dorsal wall of the head that first extends pos- 

 teriorly beneath the cuticle (fig. 15 B, pLm). The fold elongates 

 (C, Lm) and finally turns forward and downward over the other 

 mouth parts. The buds of the new mandibles and maxillae are formed 

 directly from the epidermis retracted into the bases of the larval 

 organs. An early stage of their development still within the larval 

 cuticle is seen at C of the figure taken from Thompson. The labium 

 and the hypopharynx of the larva, as already shown, are greatly re- 

 duced and united in an area between the mouth and the hypostomium, 

 the two components being separated only by the opening of the 

 salivary duct. In Aedes the labiohypopharyngeal complex as shown by 



