242 ZOOLOGY FOR MEDICAL STUDENTS chap. 



introduced into France caused immense destruction to vines, and the 

 Coccidae or Scale-insects also belong to this group. In the Coccidae 

 special secretions are commonly produced by the skin of the adult female : 

 white wax, shellac, cochineal, are examples of such secretions of economic 

 value. In the second section of the Hemiptera — the Heteroptera — in 

 which the fore-wings are protective, are included a large number of 

 insects which normally suck the juices of plants but which in some cases 

 have developed the blood-sucking habit. The bed-bug {Cimex or 

 Acanthia) with a very thin flattened body of a brownish colour and the 

 Benchucas of South America (Conorhinus) are bugs which are important 

 to man both by their unpleasantness and by the fact that they play a 

 part in spreading protozoan microbes (pp. 49, 50). From the form of 

 their body they are able to hide in very narrow crevices in walls and 

 furniture and are consequently difficult to eradicate. Thorough fumiga- 

 tion or " gassing " is the most effective means of dealing with badly 

 infested houses. 



The group Neuroptera, which is now usually broken up into a 

 number of independent groups but is retained here for the sake of 

 simplicity, includes a large number of insects with biting mouth-parts 

 and with two pairs of similar membranous wings, the nervures of which 

 usually form a network of small meshes. 



The Termites are well known from the fact that they commonly live 

 in immense communities with highly complex social organization and 

 marvellous differentiations of the individuals for different functions in the 

 community. The most remarkable of these differentiations is that the 

 reproductive functions are concentrated in a single pair of individuals, 

 the king and queen. In some species, especially among the tropical 

 African termites, the queen attains to a gigantic size owing to the great 

 development of the ovaries, and during adult life continues to lay eggs, 

 sometimes at the rate of about one per second. Although the actively 

 reproductive individuals are only a, single pair there exist also reserve ' 

 individuals to take their place in case of accident. These reserve in- 

 dividuals normally remain in an immature state but the community is 

 able in case of emergency, by some unknown method of treatment, to 

 bring about sexual maturity and qualify the reserve individual to take 

 the place of the original king or queen. 



Termites, as is suggested by the popular name " white ants " — mis- 

 leading, as they have nothing to do with the true ants — have their 

 cuticle for the most part thin and transparent, allowing the white fatty 

 body to show through it. In correlation with this transparent nature of 

 the body-wall termites habitually avoid the light : they live within nests 



