REPORT ON MOSQUITOES. 63 



No one genus of mosquitoes can be considered a universal 

 •disease carrier, and some species that are not known to carry- 

 diseases of man do carry diseases of birds and probably of other 

 animals. 



In New Jersey the only diseases influenced by mosquitoes are 

 the various forms of malarial fever, and only the species of the 

 g-enus Anopheles are known to be active in its transmission. To 

 te entirely accurate, only one of our species, A. mac^tUpennis, 

 has been actually demonstrated as a carrier of the disease. Neither 

 punctipennis nor crucians have been definitely proven to be hosts 

 for the parasite; but, as in other countries, other species than 

 maculipennis are known to be dangerous, the two species men- 

 tioned must be looked upon with distrust until actual experiment 

 proves them harmless. I have elsewhere given the reason why 

 this demonstration could not be made in the present investigation. 



The entire life cycle of the malarial parasites has been worked 

 out and the history of the investigation and of the actual experi- 

 ments made are detailed by Dr. H. P. Johnson in an appendix 

 to my Report to the Experiment Station for 1902. For present 

 purposes the experiment record may be omitted and Dr. Johnson's 

 account of the parasite, its development and its relation to both 

 man and mosquito is given, with such additions and explanations 

 as the change in form makes necessary. So far as possible matter 

 directly quoted is given in quotation marks. 



"There is a widespread misapprehension regarding the way 

 in which malaria is transmitted bv mosquitoes. Many who 

 tuihesitatingly accept this view are unable to explain upon what 

 foundation it rests, or why it has so quickly won the acceptance 

 of biologists the world over. Many, even of the medical pro- 

 fession, attach little or no importance to the really great differ- 

 ences in the modes of existence of the various disease germs. 

 Hence it is not surprising that they should regard the malarial 

 organism as a germ of the same sort as bacteria, endowed with 

 the well known power of most bacteria to live outside the animal 

 body and withstand cold, heat, dryness and other adverse condi- 

 tions. If this were so, modes of transmission other than that 

 by mosquitoes would require the most careful consideration. No 

 reputable pathologist or bacteriologist would venture to assert 

 that one might not contract malaria as one contracts typhoid or 

 diptheria or smallpox. The simpler the life history of a patho- 

 genic organism, the greater the variety of conditions under which 

 it can lead an active existence. As compared with bacteria, the 

 life histoi-y of the malarial organism is exceedingly complex ; 

 accordingiv we find its conditions of existence vigorously 



