196 TROPICAL MEDICINE AND HYGIENE 



This species is oviparous, and the eggs are fusiform 

 in shape. The larva is hexapod, but the legs are only 

 represented by tubercles. The nympha has four pairs 

 of legs and is formed after the second moult. There is 

 no evidence that this parasite is more common in the 

 Tropics than elsewhere. 



Scabies. A pustular eruption similar in its characters, 

 and due to apparently the same acarine, Sarcoptes scabiei, 

 occurs in most tropical countries. It is not markedly 

 more common than in temperate regions. The pustular 

 skin eruptions known as coolie itch, itch, craw-craw, &c., 

 are very common, bacterial as a rule, and due to various 

 causes, but rarely to the S. scabiei. True itch, when it 

 does occur, would no doubt be included in these popular 

 designations. 



DlPTERA. 



Dipterous insects are injurious in many ways : (i) They 

 may, as in the case of mosquitoes, be a necessary host of 

 human parasites, e.g., Filaria bancrojti and the parasites 

 of malaria, or in the case of the Glossina be a host of 

 Trypanosome gambiense or T. rhodesiense, or, as in Chrysops 

 dimidiata, be the intermediate host of Filaria loa. 



(2) They may be mechanical carriers porters of 

 various bacilli. 



(3) They or their larvae may be directly injurious 

 by penetrating the skin, inflicting wounds, or injecting 

 poisonous venoms. 



The dipterous insects capable of penetrating the skin 

 and sucking blood are numerous. They include amongst 

 the Nematocera many species of mosquitoes (Culicidae), 

 of Chironomidae and Simulidae either of these when 

 small are popularly know as " sand-flies " Psychodidae, 

 owl midges, and amongst the Brachycera, the Tabanidae, 

 Tabanus, Chrysops, Haematopota, &c. Amongst the 

 Muscidae the various species of tsetse-fly (Glossina), 

 Stomoxys, Haematobia, &c., and amongst Pupipara the 

 Hippoboscidae are biting flies and some are known 

 carriers of disease. 



