240 THE MOSQUITOES. 



midges, the "jejen" of Cuba, is a great scourge, its small 

 size enabling it to enter eyes and nostrils. The larva of 

 Chironomus is a red worm -like creature; the pupa has a 

 tufted head. 



2. Simulidae or Buffalo Gnats. These are small blood- 

 thirsty insects only about 1/8 of an inch in length. The 

 thorax is humped, the legs are short and the proboscis 

 short and inconspicuous. 



One species, the S. damnosum, known by the natives of 

 Uganda as "Mbwa," is greatly dreaded; its bites causing 

 swellings and sores. 



3. Psychodidae. These are small, hairy, slender midges, 

 with long legs and a long proboscis. They are only 

 about if 1 2 of an inch in length. 



Mosquitoes have 3 main parts of the body the head, the thorax and 

 the abdomen. On the head, the space behind the two compound eyes 

 is called the frons, in front, and the occiput posteriorly. 



The nape is back of the occiput. The bulbous prolongation of the 

 frons which projects over the attachment of the proboscis is. the 

 clypeus. The clypeus is hairy in the Culex; scaly in Stegomyia. The 

 proboscis is straight in all mosquitoes of importance medically. It 

 consists of a fleshy, scaled, gutter-shaped portion beneath, known as the 

 labium, which terminates in two hinge-joint processes the labella. 

 At the end of the labium is a thin membrane (Button's membrane). 

 It is through this that filarial embryos are supposed to pass on their way 

 from the interior of the labium to enter the person bitten. The labium 

 may be considered as the sheath of a knife, holding and protecting the 

 slender, blade-like penetrating organs. Lying in this groove we have, 

 from above downward, the horseshoe-shaped labrum epipharynx, 

 the under surface of which is open. This when closed by the under- 

 lying hypopharynx forms a tube through which the blood is sucked up 

 by the mosquito. In the hypopharynx, which somewhat resembles a 

 hypodermic needle, is a channel, the veneno-salivary duct. It is down 

 this channel that the malarial sporozoite passes. There are 2 pairs of 

 mandibles and 2 pairs of maxillae on either side of the hypopharynx 



