Some Habits and Hosts of Bird Ceratophylli. 89 



Ceratophyllus insularis, Rothsch. 

 5. L. aryentatus, cliff, nr. Todhead, Kiuneff, 19 : iv : 09. 



Ceratophyllus borealis, Rothsch. 

 $. L. aryentatus, cliff, Todhead, A. MTnnes, 15 : vi : 09. 



Ctenophthalmus Agyrtes, Heller. 



5>, Talpa europma, 16:vi:09; £, domestic Cat, August; £, M. decumanus, 



6 : x : 09. All from Kinneff, J. R. Fraser. 

 £ and 3 <?<j>. M. decumanus, Mill of Allardyce, Arbuthnot, J. R. F., 14 : vi : 09. 

 J. Erinaceus europceus, Colinton, J. M. Bruce, I6:vii:09. 

 ?. M. decumanus, Kirkcaldy ( Fifeshire), W. Mitchell, 21 : x : 09. 



2 $$. M. decumanus, Lochgelly, J. Brown, 21 : x : 09. 



3 $5. M. decumanus, Dunskeig Farm, Clachan, P. MTntyre, per D. M'Rae, 



25:xi:09. 



Relation of bird Ceratophylli to their hosts. — The common, and in some 

 ways not unreasonable, impression that particular fleas are attached to 

 particular hosts whose range I determines that of the parasite, is only slightly 

 supported by the available evidence. The rule evidently holds for species 

 like styx, columbcv, and hirundinis which are normally attached to one host. 

 It is likely that within this group dalei and farreni fall (with C. urbica as 

 their true host), though both species (one wonders if it were by coincidence 

 only) were originally made known from nests of the Wood-Pigeon 

 (G. palumbus). 



At the other extreme are forms like gallince, gallinulce, garei, and 

 fringillce which feed on so many hosts as to make classification seem, at first 

 sight, hopeless. Gallinulce, indeed, seems to have no special preferences. It 

 has been very widely taken in Scotland, the only noticeable gap hitherto 

 being among the Ducks. Fringillce, a well-named species, haunts the nests of 

 Sparrows and smaller Passerines generally. Gallince has a range, hardly if at 

 all inferior to that of gallinulce. Waders, moor and shore birds, and Ducks 

 seem the usual host of garei, but the presence of this species is determined 

 rather, I think, by the locality than by the hosts. One always expects to 



1 A flea may have a range exceeding or falling short of that of its usual host. In 

 Orkney, Hystrichopsylla talpce has recently been found by Mr Ellison, though the Mole 

 (Talpa europma) is absent. Again, Xenopsylla cheopis has occurred in Britain only as a 

 casual importation, though suitable hosts abound here. It is plentiful on Mils spp. in 

 India. On the other hand G. fasciatus, a common rat flea in Britain, is relatively rare in 

 India, forming only a small proportion of the fleas taken by the Plague Commission. 



As the environmental conditions of fleas must be fairly equable when on the host, 

 other factors must limit their distribution in lands where the same hosts occur. Possibly 

 these factors are climatic. They may not affect the imagines directly, yet their influence may 

 be potent on ova and larva?. 



YOU XVIII. G 



