THE MALARIAL PARASITE 175 



thirteen-jointed antennae bearing whorls of bristles, which are 

 specially long in the male, giving the antennae a feathery ap- 

 pearance. These features are shared by some other closely 

 allied dipterous insects, but Culicidae are characterised by two 

 features ; they have a long suctorial proboscis, and the veins 

 and lower margins of the wings are covered with minute 

 scales. They lay their eggs in the water and the larvae hatched 

 out from the eggs are aquatic and incapable of sustaining life 

 if placed in the dry. Hence the stories which from time 

 to time appear in newspapers attributing unusual swarms of 

 mosquitoes in hotels to the introduction of eggs and larvae 

 in the luggage of visitors arriving from tropical countries are 

 mere fables, founded on a complete ignorance of the natural 

 history of the insects. The most common culicid in Great 

 Britain is the so-called grey gnat, Culex pipiens, a species 

 which is also widely distributed in other countries. The 

 female of C.pipiens for it is only female gnats and mosquitoes 

 that suck blood is as pertinacious a blood-sucker as any 

 mosquito, but does not serve as the intermediate host of the 

 parasite of human malaria. It is an interesting fact, however, 

 that birds suffer from a form of malaria analogous to that of 

 man, and similarly caused by a sporozoon parasite infesting 

 the red blood corpuscles. Culex pipiens is the intermediate 

 host of avian malaria, but is impervious to human malaria. 

 On the other hand Anopheles, to which the name mosquito may 

 conveniently be restricted, is impervious to avian, but is the 

 intermediate host in human malaria. 



To understand the manner in which Anopheles introduces 

 the malarial parasite into the blood, it is necessary to know 

 something about the structure of the proboscis and its action 

 in blood-sucking. Only the female proboscis will be described, 

 the mouth parts of the male being incapable of perforating 

 the skin. 



The mouth parts of an undifferentiated insect such as a 

 cockroach or grasshopper consist of the following parts : 

 (i) A median unpaired upper lip or labrum. (2) A median 

 internal membranous lobe known as the tongue, lingula or 

 hypopharynx. (3) A pair of chitinous biting jaws, the 

 mandibles. (4) A pair of maxillae, consisting of two basal 

 joints, of which the second bears on its inner side two biting 

 lobes and on its outer side a jointed tactile appendage or 



