34 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I39 



separated by a constriction. The histology of the glands in Anopheles 

 larvae has been described by Jensen and Jones (1957). In Anopheles 

 albimanus the globular anterior part of each gland consists of 12 to 15 

 large cells; the pear-shaped posterior part contains 50 to 60 much 

 smaller cells. The glands of opposite sides are connected by a strand 

 of nephrocytes. In other genera the relative size and shape of the 

 two gland parts differ in various ways. 



The nervous system. — The central nervous system of the larva in- 

 cludes a brain and suboesophageal ganglion in the head, and a ventral 

 chain of segmental ganglia in the abdomen united by paired connec- 

 tives. The last ganglion is that of the eighth abdominal segment. 



The reproductive organs. — Rudiments of the reproductive organs 

 are present in the young larva in a very elementary state ; they 

 slowly develop during the larval life. 



Food reserves. — The insect larva has no idea of the meaning of its 

 life or of what is to become of it. Its hereditary factors automatically 

 determine its destiny by converting it into a pupa and finally into an 

 adult. Yet, physiologically, the larva is loaded with responsibilities. 

 Not only must it maintain its own existence, but at the same time it 

 must provide for the future nutritional needs of the pupa and for its 

 transformation to the adult. In the mosquito pupa there is a minimal 

 breakdown of larval tissues to furnish food for the developing adult 

 organs. The active mosquito pupa, moreover, is not a "resting stage," 

 and, since it cannot eat, it is dependent upon the larva for everything 

 except the air it breathes. An important function of the larva, there- 

 fore, is the storage of food reserves in its body to maintain the pupa 

 and to insure the development of the adult. Only when the winged 

 adult finally emerges from the pupal skin can the mosquito again take 

 food and become once more an independent, self-sustaining insect. 



The elaboration and storage of food reserves in the body of the 

 fourth-instar mosquito larva is the subject of a special study by 

 Wigglesworth (1942). The stored materials include principally pro- 

 tein, fat, and glycogen, which are shown by experiments to be rapidly 

 consumed when the larva is subjected to starvation, and replenished on 

 subsequent feeding. Normally, it is to be supposed, the stored prod- 

 ucts are passed on intact to the pupa, but Wigglesworth does not go 

 into this phase of the subject, or follow the utilization of the reserves 

 by the pupa. The matter, however, is well-enough known in other 

 insects. 



II. THE PUPA 



The active pupa is familiar to all students of mosquitoes after its 

 ecdysis from the larva. The fact, however, that it is already fully 



