

TRANSMISSION OF DISEASES BY INSECTS 251 



emanations from the marsh and taking no precautions except to screen 

 their house carefully against mosquitoes and to retire indoors before 

 the insects appeared in the evening. Simply by excluding Anopheles 

 mosquitoes, with which the Campagna swarmed, these investigators 

 remained perfectly immune from the malaria which was ravaging the 

 vicinity. 



In a later experiment on the island of Formosa, one company of 

 Japanese soldiers was protected from mosquitoes and suffered no 

 malaria, while a second and unprotected company contracted the 

 disease. 



The evident preventive measures to be taken against malaria are 

 (i) the avoidance of mosquito bites, by means of screens, and washes of 

 eucalyptus oil, camphor, oil of pennyroyal, oil of tar, etc., applied to 

 exposed parts of the body; (2) the isolation of malarial patients from 

 mosquitoes, in order to prevent infection; (3) the destruction of mosqui- 

 toes in their breeding places, especially by the use of kerosene and by 

 drainage. During unavoidable exposure in malarious regions, quinine 

 should be taken in doses of six to ten grains during the day at intervals 

 of four or five days (Sternberg) . 



In Macedonia in 1916 there were some 800,000 cases of malaria, 

 with 2,000 deaths in the French and Allied army. Where the disease 

 was most severe Anopheles mosquitoes were present in enormous num- 

 bers. A striking peculiarity of this epidemic was the marked failure 

 of quinine as a preventive or remedy. This failure was explained as 

 being due to the development of quinine-resistant strains of the malaria 

 parasites. 



Culex and Anopheles. More than five hundred species of mosqui- 

 toes have been described. Of these only the genus Anopheles transmits 

 malaria to man; though in India, Ross found that Culex transmits a 

 form of malaria to sparrows. These two common genera are easily 

 distinguishable. In Culex the wings are clear; in Anopheles they are 

 spotted with brown. In Culex when resting, the axis of the body 

 forms a curved line, the insect presenting a hump-backed appearance; 

 in Anopheles the axis forms a straight line. Culex has short maxillary 

 palpi, while in Anopheles they are almost as long as the proboscis. The 

 note of the female Anopheles is several tones lower than that of Culex , 

 and only the female is bloodthirsty, by the way. As regards eggs, 

 larvae and pupae, the two genera differ greatly. The eggs of Culex are 

 laid in a mass and those of Anopheles singly; the larvae of Culex hang 

 from the surface film of a pool at an angle of about forty-five degrees, 



