NO. 8 ANATOMICAL LIFE OF THE MOSQUITO — SNODGRASS 6j 



Otherwise the membrane of the whole basal area is occupied by irregu- 

 lar thickenings or weak sclerotizations that are hardly sclerites and 

 seem to have no mechanical significance. They are better developed 

 in Anopheles (B) than in Culex (A). The same structure in modified 

 form is present also in some related Nematocera, but not in Tipulidae. 



The wing mechanism of extension and flexion is not understood, 

 but all the direct muscles of flight appear to be attached on the basal 

 lobe. The indirect flight muscles are as fully developed as in any 

 other fly. They include great masses of dorsal longitudinal fibers and 

 lateral vertical fibers that almost completely fill the thorax. The 

 weight of the flight muscles of Aedes has been calculated by Hocking 

 (1953) as from 16.5 to 18.7 percent of the total body weight, which, 

 however, is small as compared with Tabanus in which the flight 

 muscles are 23 to 35 percent of the body weight. 



The rate of the wing vibration in flight, measured in wing beats per 

 second, is given by Sotavalta (1947) for females as 165 to 196 for 

 Culex pipiens, 165 to 247 for Anopheles maculipennis, 241 to 311 for 

 Aedes cantans and Aedes punctor. With males the rate is consistently 

 higher, from 330 to 587 beats per second by Anopheles and Aedes. 

 Hocking (1953) has measured the flying speed of five species of 

 Aedes. In ordinary cruising flight they go from 75 to no centimeters 

 per second, but for short distances they can make 220 to 252 centi- 

 meters in a second. 



The legs of the mosquito have no unusual features, except for their 

 length and relative slenderness. Each leg (fig. 17 B) has the usual 

 six segments of an insect leg, a coxa, trochanter, femur, tibia, tarsus, 

 and pretarsus. The long tarsus is subdivided into five tarsomeres. The 

 pretarsus has two decurved claws but no arolium. In some species, as 

 in Culex, the foot is provided with a pair of small padlike pulvilli ; in 

 others there is only a heel-like hairy swelling at the bases of the claws. 

 Most mosquitoes, however, whether they have foot pads or not, are 

 able to cling to smooth vertical surfaces, such as window panes or the 

 walls of a glass jar. 



THE ABDOMEN 



The abdomen of the adult mosquito (fig. 27 A) is broadly joined to 

 the thorax and tapers posteriorly. The tergal and sternal plates are 

 separated on the sides by membranous areas containing the spiracles, 

 which are present on segments I to VII. In each sex the abdomen has 

 10 segments, as in the pupa, but in the females of some species the 

 eighth segment is ordinarily retracted into the seventh, and in the 

 male the ninth segment is concealed within the eighth. 



