194 MEDICAL ENTOMOLOGY 



up the consideration of the genera and species it will be convenient to 

 describe some of the common types of scales met with. 



A true Sca * e can ^ e rec g n i ze d by its ribbed appear- 

 ance, the ribs simulating the veins of the wing of an 

 insect in miniature. It is nearly always attached by a delicate stalk, 

 which is often bifid. Its free end may either be flat with minute serrations, 

 or convex with projecting sides; or sloping gently to a blunt point. 

 On the head of a mosquito there are, as a rule, three types of scales to be 

 seen. 1. Upright curved scales. 2. Upright forked scales. 3. Broad 

 flat scales which are closely applied to the surface. All the three types 

 of scales are found on the vertex, and they exhibit great variation in 

 colour. 



On the thorax there are commonly four types of scales in addition to 

 hairs. 1. Upright curved scales, found all over the thorax and scu- 

 tellum. 2. Spindle-shaped recumbent scales, varying in size, and scat- 

 tered irregularly over the surface. 3. Flat scales similar to those on the 

 head, and found chiefly on the scutellum and just below the roots of the 

 wings. 4. Long narrow twisted scales, well marked in the mosquitoes 

 of the Mucidus group. 



The scales on the abdomen are best seen in the culicine mosquitoes, 

 in which they form a dense covering, and are broad and flat ; most of 

 the anophelines have none of these scales, but a few are seen in some 

 species, either forming tufts at the sides of the segments, or scattered 

 irregularly at the lower end of the abdomen and on the external geni- 

 talia. 



The veins of the wing are clothed with a double row of somewhat 

 broadly expanded flat scales, and in addition there are often lateral ones 

 of varying shape, some long and straight, others curved. In some 

 mosquitoes the scales on the wings are more or less ovate, the apical 

 border being convex. The wing fringe has two types of scales, one 

 short, the other longer ; there are also small border scales, which are flat 

 and narrow. 



The legs are always covered with flat scales and hairs, and in some 

 species they are greatly exaggerated, and project from the surface. 



The worker will find that any species of Culex, Stegomyia, or Anoph- 

 eles will provide almost all the varieties of scales which are likely to be 

 met with. 



The eggs of mosquitoes are laid on water, or on any vegetable matter 

 lying on its surface ; they may either be deposited singly or in a mass, 

 adhering closely together. Most species of the genus Culex, while 



