1917 ENTOMOLOGICAL SOCIETY. 61 



parasites allied to the trypanosomes. These parasites are responsible for a num- 

 ber of tropical diseases, especially the one known as Icala azar of human beings, and 

 here the evolutive cycle is claimed by Patton to take place in the common bedbug, 

 but this, however, is not generally accepted. 



Ticks and Spirochetoses. The spirochtietes are probably protozoa. Spiro- 

 eha^tosis is also refe!rred to in the literature as Spiroplasmosis and Babesiosis. 

 These organisms are responsible for several serious, diseases of animals and two of 

 man. The organism of Texas fever of cattle, referred to in our opening remarks, 

 and which is carried by the cattle tick, is an example. The sexual repro- 

 duction of this organism in the blood of cattle is well known, but 

 tlie sexual reproduction in the tick has not 3'et been made out, although in a related 

 species, Babesia canis, of the dog, causing maligant jaundice in Africa and parts 

 of southern Europe, this cycle has been worked out by Christopher. 



The life cycle of a spirochaote has been especially worked out in the disease 

 known as spirochetosis of fowls, which occurs in southeastern Europe, Asia, 

 Africa, South America and Australia. This disease is transmitted from fowl to 

 iowl by a tick known as Argas pcrsicus. The full life cycle has been worked out 

 especially well by Balfour and Hindle, and is diagrammatically represented on the 

 accompanying slide. 



Ticks and Rocliy Mountain Spotted Fever. This is the first of the probable 

 spirochaete diseases of man carried by ticks. (Discussion and lantern slides). 



The other human disease referred to is the European relapsing f^ver, which at 

 first was supposed to be carried by bedbugs, but which has since been shown to be 

 carried by lice. 



This brings us to Typhus fever and lice. (Discussion and lantern slides). 



But now we must stop. There are many subjects in the field which we have not 

 touched. Tick paralysis, for example, is a most interesting and novel subject. 

 This disease occurs in Australia, Africa and North America. In Oregon thirteen 

 cases have been found in the practice of a single physician." The attachment of a 

 tick brings about progressive paralysis involving motor, but not sensory nerves. 

 It seems a unique malady. Hadweh and Nuttall, showing that it is not infectious 

 and that there is apparently an incubating pejriod in the tick, suggest a specific 

 caxisative organism, but others hold to the theory of nerve shock. 



Attention should also be called to the fact that, in spite of the host of dis- 

 coveries already well established, there is a danger in our tendency to exaggerate 

 the importance of insect transmission, and to overlook, even in cases where insects 

 may occasionally be concerned, the greater importance of other modes of infection. 

 This is indicated by Sambon's theory of transmission of pellagra by Simulium — a 

 theory which was advanced with enthusiasm on the ground that it fitted into the 

 known facts in the epidemiology of the disease. It took two years of hard work on 

 the ])art of members of the force of the Bureau of Entomology, working in collabora- 

 tion with the Thompson-McFadden Pellagra Commission, to upset this theory in 

 a thoroughly scientific manner. As has been pointed out several times of late, 

 there is always considerable danger in conclusions based on epidemiological find- 

 ings. Transmisson experiments are necessary. 



One conclusion must be drawn which can hardly be disputed : There is an 

 enormous field for the entomologist in the careful study of all of the aspects of the 

 biology, of not only those insects which have already been shown to be disease 

 carriers, but of those which are likely to be implicated. It is to the trained 

 economic entomologist that we must look for the methods of destruction of those 



