STUDIES ON AVIAN H^EMOPROTOZOA. 653 



obtained, and their comparison with various flagellates 

 described in blood-sucking Invertebi'ates (cf. below), leaves 

 no doubt whatever in my mind that these bird-trypanosomes 

 have some alternate (doubtless insectan) host. But it is 

 quite possible that, in the present instance, some other 

 insect than Culex performs this role. I endeavoured to 

 ascertain what other biting insect was likely to be concerned. 

 Mr, Austen, of the British Museum, very kindly informed 

 me of a small hippoboscid fly, of the genus Ornithomyia, 

 which is an ectoparasite of various birds, especially to be 

 found on nestlings.^ Up to the present, however, I have been 

 unable to obtain a supply of these insects. 



It seems to me not at all unlikely that it is in this 

 direction one must look for the alternate host. If this be 

 the case, it is very probable that infection usually occurs 

 while the birds are quite young, and before they leave the 

 nest. 



Early in the autumn I obtained a young redpoll, infected 

 with trypanosomes, which could not have been more than two 

 months old, if that, when bought ; and as most of these little 

 cage-birds are caught, I am told, as soon as they can look 

 after themselves and before they finally leave the nest, this 

 may very well be a case in point.- Unfortunately, owing to 

 the hampering restrictions of wild birds' protection acts, etc., 

 I could not get hold of any nests containing fledgelings for 

 examination. Towards the end of the close season a bird- 

 seller did procure a chaffinch nest for me, from which the 

 young birds only flew away as he approached. This was well 

 searched for insects, but contained none. I may add that I 

 have never noticed any insects (fleas, lice, etc.) on my birds 



^ The Sergents have recently found (30) that a hippoboscid fly- 

 belonging to the genus Lynchia is most probably concerned in the 

 transmission of the Halteridinm of the pigeon. Lynchia, however, 

 is not met with in Britain. 



- An interesting obsei'vation noted by Danilewsky of trypanosomes 

 being present in a young roller-liird only a week old also supports this 

 view. The only alternative would be that of hereditary infection, which 

 is extremely doubtful. 



