192 INSECTS AND MAN 



chief point of interest lies in the fact that it is more truly 

 parasitic than other fleas, with the exception of the jigger 

 flea. It does not bury itself beneath the host skin like 

 the latter species, but it inserts its mouth organs deeply 

 and firmly into the host and there remains affixed. The 

 neck and head, especially the region of the eyes, are the 

 favourite points of attack, and the results are swellings and 

 ulcers, which often result in death to the host. 



AIR-SAC MITES 



As long ago as 1858, a German scientist named Garlach, 

 while dissecting some chickens, by chance examined their 

 respiratory organs, and there discovered some whitish, 

 rounded mites, so small as to be only just visible to the 

 naked eye. Our excuse for mentioning these minute 

 parasites is not that they are particularly common, or even 

 specially injurious to their hosts, but because in habit 

 they are dissimilar to other closely related species, which 

 are all external parasites. The creatures, which have been 

 named air-sac mites, and are known to science as Cytodites 

 nudus (fig. 55), normally inhabit the air passages of gal- 

 linaceous birds, where they may cause inflammation of the 

 lungs : at times they occur in other organs, and have even 

 been found in the heart, where they set up endocarditis. 



Though closely related to the mange mites, Sarcoptes 

 species in fact Cytodites was at first believed to be an 

 internal form of these mites it differs from them in many 

 important characters. The mange mites have mouths 

 adapted to cut and tear flesh and so enable them to burrow 

 below the skin : the air-sac mites have tubular sucking 

 mouths , quite incapable of biting or piercing flesh. Although 

 they are unable to rupture even the delicate mucous mem- 

 branes on which they live, their constant movements over 

 these surfaces set up a considerable amount of irritation, 

 despite the fact that their feet take the form of suckers 

 and are not provided with claws. 



