316 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 5 



least such primary cases that form a nidus from which infection may 

 later spread. 



2. That, while the tick may be the general carrier of the disease 

 among animals/ some other carrier such as Stomoxys is necessary to 

 transmit the virus to human cases. 



3. That the introduction of the disease into Massachusetts is so 

 recent that there has not yet been time for it to become equally abun- 

 dant each year. Such a condition of approximately equal annual inci- 

 dence must necessarily come about finally, on the basis of the above 

 assumption, as a result of hold-over cases, and of irregularities in the 

 length of the life cycle of the tick. 



One habit of this tick might throw doubt upon such an hypothesis, 

 since unlike the cattle tick, Margaropus annulutus, AmhJyomma drops 

 from its host to molt and must frequently attach itself to several 

 animals during its lifetime. If it remained attached to the same 

 animal continuously as does the cattle tick, a biennial reinfection would 

 necessarily result, since with Texas Fever fresh animals are infected 

 by the Piroplasma parasite only through young or seed ticks hatching 

 from eggs laid by infected female ticks capable of transmitting the 

 disease to their offspring through the eggs which they deposit. In the 

 light of Lounsburj^'s observations, however, such an objection loses 

 its force. 



Account of the Area Investigated 



In the following short accounts of the towns visited during the 

 summer we have endeavored to give only such data as appear to 

 have a bearing upon the foregoing discussion. 



Waltham. Population approximately 28,000. 



Waltham is in Middlesex County on both sides of the Charles 

 River, ten miles west of Boston. It is connected with Boston through 

 Newton, both by trolley and by the Fitchburg division of the Boston 

 and Maine Railroad. It is principally engaged in the manufacture of 

 watches, although there is also a large cotton mill, a bleachery and 

 dye works in the toAvn. 



I In this connection it is instructive to note that Lounsbury has shown that canine 

 pii'oplasmosis in South Africa which is transmitted by a tick {Hcemaphysalis leachi) 

 is not transmissible until after a complete life cycle of the tick. Thus it is spread 

 not by the larvee from infected mother ticks, but only by those which, reared from 

 eggs deposited by infected mother ticks, have passed through two preparatory stages 

 and attained the adult condition. Here, contrary to what prevails in the spread of 

 Texas Fever, recurrences of cases from individual infections are delayed till a com- 

 plete life cycle of the tick has been undergone. If we have to deal with a tick 

 having a two-year life cycle, such a fact is at least significant in relation to the 

 apparent biennial fluctuation of acute epidemic poliomyelitis. 



