The Head, Thorax, and Abdomen 



Attached to the maxillae are two maxillary palpi. The palpi 

 of " anopheles " mosquitoes are very prominent organs, as long as 

 the proboscis in both sexes, and clubbed at their extremity in the 

 males. (PI. Ill, figs. 3, 4). 



The palpi are less prominent organs in the genera Culex, 

 Stegomyia, Panoplites, etc., except in the case of the males, in which 

 they are even longer than the proboscis, but in the females of these 

 genera they are rather minute structures, just visible to the naked 

 eye. (PL III, figs. 1, 2). 



The thorax is mainly composed of the middle division or 

 mesothorax ; it is large and convex. Behind the main part of the 

 thorax, a prominent ridge runs between the bases of the wings ; this 

 ridge is called the " scutellum." Posterior to the scutellum, a 

 horse shoe-shaped area is seen ; this is the " metanotum." 



Projecting laterally, behind the metanotum, the club-shaped 

 halteres will be noted. 



The abdomen is more slender than the thorax, and consists of 

 nine segments : eight of these are easily seen, each segment being 

 composed of a dorsal plate or tergum, and a ventral plate or 

 sternum, joined together by a soft membrane. The anus opens 

 on the ventral surface of the eighth segment, while the genital 

 opening is on the ninth segment, and to this segment are attached 

 the genital ia. 



Attached to the under-surface of the thorax are the six legs, 

 three on each side (anterior, middle, and posterior pairs of legs). 

 Each leg consists of the following parts : Two small segments, 

 the coxa and trochanter (these cannot be seen from the dorsal 

 aspect), two longer segments, the femur and tibia, and, lastly, five 

 tarsal segments. The first tarsal segment is sometimes called the 

 metatarsus. Between the tarsal segments are the tarsal joints. 



The wings of mosquitoes are mapped out with veins which are 

 covered with scales. These veins have a very definite arrangement, 

 and a knowledge of the names applied to them is essential in dis- 

 tinguishing the different species.* 



The external or anterior border of the wing is called the costa. 



Running parallel with the costa is the first longitudinal vein. 







* The reader will be greatly helped by following these veins as well as other structures 

 noted, on the descriptive diagram of a female anopheles (coloured plate No. I). 



H] 



