5 
External Structure of a Mosquito . 
a suture a portion of the mesothorax called the scutellum (sc). 
The scutellum is usually trilobed, a central and two lateral 
lobes ( Gulex, &c.), but in Gorethra it consists of a single piece 
only; its posterior border is always provided with a row of large 
and some small bristles—the “posterior border bristles”—which 
are in some cases of specific value in regard to their number 
on the mid lobe ; there are also numerous bristles on the lateral 
lobes ; this portion of the mid-body is more or less covered with 
scales; the metanotum (Fig. 6) is the smooth, very convex, 
nude, back portion of the thorax, large and distinct in Culex 
and Anopheles , but more or less hidden under the mesothorax in 
Megarhinus* ; in one genus, Wyeomyia (Fig. 6, II.), it carries a few 
chaetae, and in Triehoprosopon (III.), .scales as well as chaetae. 
The sides or pleurae can also be seen to be composed of three 
chief parts, each marked by the coxae of the three pairs of 
sc sc sc 
I. Culex. II. Wyeomyia. III. Triehoprosopon. sc —. scutellum. 
legs. There is present in front of the fore coxa an oval scale 
which covers the prothoracic spiracle, not easily seen however ; 
another spiracle exists on the mesothorax in front of the origin 
of the wings ; I have never seen the metathoracic spiracle, but it 
is said to exist ; the mesopleura is the space between the fore and 
mid coxae which carries the fore wing, the mid leg, and a spiracle ; 
the metapleura lies behind, and carries a hind leg and haltere. 
(3.) The abdomen is more slender than the thorax, and 
is narrower and more pilose in the £ than in the 5 • It 
consists of nine segments ; each segment is composed of a 
dorsal plate or tergum, and a ventral plate or sternum, 
* Usually spelt Megharina. The name originally given by Desvoidy is 
spelt Megarhinus. The former hacl previously been used for some of the 
Tipulidae. 
