1911] Cole, Trematode Parasite of English Sparrow. 47 



office: There was a rainy spell from May 15 to May 23, and a 

 smaller one June 2-6; the conditions thereafter were generally 

 dry, with light falls of rain on the 18th, 26th and 27th. July 

 was also predominatingly dry, with light rains on the nth, 12th, 

 14th, 17th and 24th. Thereafter there was no rain to speak of 

 till a wet spell of a week or so which began August 13. From 

 the above it will be observed that the cessation of the finding of 

 the parasite, on June 14, followed very closely the beginning of 

 the dry period, on June 7. From this it might be inferred that 

 the accession of the parasite to its final host is in some way 

 dependent on moist conditions, and that conditions of dryness 

 cause a break in the life cycle. Those sparrows found parasitized 

 after June 7 might very well have received their infection prior 

 to that date. 



As regards the seriousness of the infection to the sparrow 

 host, some evidence has accumulated suggesting that it may in 

 certain cases, at least, prove fatal. During the period of the 

 epidemic of infection several sparrows were found dead near 

 the barns and poultry yards, and the majority of these showed 

 severe Monostoma infection. This is, of course, only presumptive 

 proof that death was due to the parasite, but as such it is fairly 

 strong. 



Finally, the points which have been learned from the epidemic 

 under discussion may be summed up as follows : 



1. Only young sparrows were affected; in no case were the 

 parasites found on the adults. 



2. Young sparrows were infected even before leaving the 

 nest. This would seem to lend some support to the suggestion 

 of Willemoes-Suhm (1873) that some one of the sparrow's 

 insect parasites may serve as the intermediate host. 



3. Infected sparrows were found only during and for a short 

 time subsequent to wet weather; the epidemic apparently ended 

 with the advent of dry conditions. It is difficult to see why the 

 parasite should be influenced in this way if its life cycle is so 

 simple as suggested in the paragraph above. 



4. The sparrows may still fly about and feed, even when 

 severely infected with the parasites, but they are hampered in 

 their flight, and probably in some proportion of cases, at least, a 

 fatal result ensues. 



