NO. 8 ANATOMICAL LIFE OF THE MOSQUITO — SNODGRASS 29 



the surface it hangs from the end of the siphon with the spiracles ex- 

 posed to the air (G). Two strands of slender muscle fibers traverse 

 the tube and converge to attachments on a strong apodeme from the 

 terminal apparatus. 



An extensive comparative study of the peritremal structure has 

 been made by Montschadsky (1930) from a taxonomic standpoint. 

 His illustrations are not realistic since they appear to have been drawn 

 from flattened specimens, and the sclerotic parts are overemphasized 

 by an unnaturally dark tone, but they show the great specific variation 

 in the pattern of the peritremal lobes. 



Glands associated with the spiracular apertures have been described 

 by Keilin, Tate, and Vincent (1935). The secretion is oily and serves 

 to give a hydro fuge quality to the peritremal surface, which prevents 

 wetting and the entrance of water into the spiracles. 



Though the respiratory siphon is primarily constructed for breath- 

 ing air at the surface of the water, in species of Mansonia and a 

 species of Ficalbia it is modified for insertion into the roots of aquatic 

 plants. The siphon tapers distally and the apex is armed with spines, 

 teeth, and hooks, which, operated by the inner muscles of the tube, 

 enable the larva to insert the tip of the organ into the plant. In 

 Mansonia indubitans (fig. 11 A) the siphon is large, conical in shape, 

 and narrowed at the distal end. The apex is not sharp, but is armed 

 with a pair of strongly toothed movable lobes (B), which can be re- 

 tracted and brought together, or protracted with the teeth turned out- 

 ward. The siphon in this case is a cutting and not a piercing instru- 

 ment. It contains only one tracheal trunk, formed by the union of 

 the dorsal body trunks in the eighth abdominal segment, and there 

 is a single median, ventral spiracle between the bases of the toothed 

 lobes. These larvae live entirely submerged and obtain their air from 

 the air channels of the plant, to which they remain attached. 



According to Iyengar (1935a. 1935b) species of Mansonia in India 

 attach themselves only to the water plant Pistia stratiotes. To insert 

 the siphon the larva moves backward with the siphon held horizon- 

 tally and thrusts the tip against the root. It then wriggles actively 

 backward, while it operates the apical armature with muscles attached 

 on a rodlike apodeme, until the end of the siphon penetrates the root 

 deep enough to enter an air chamber, when apical hooks anchor the 

 larva to the root. The adult female lays her eggs only on submerged 

 leaves of the Pistia plant, thrusting her abdomen into the water to do 

 so, and where Pistia is not present she will lay no eggs. 



While most other mosquito larvae spend most of their time at the 



