12 
Observations on British Rat-jieas 
iu certain districts and the average number of (7. agyrtes there any 
more than we could with C. fasciatus. Thirty-five C. agyrtes were 
taken from “ nestling ” rats (about 30 per cent.), while only five were 
taken from about 30 rats dead of injury or disease. They may leave 
their host very rapidly after its death. 
The seasonal variation of C. agyrtes is shown in Chart I to be 
apparently dependent on temperature and moisture. In Chart III, 
however, it is seen that although there is a steady fall fi’om month to 
month in the average number of fleas per rat, yet the temperature and 
humidity records do not show the same curve. We cannot explain this. 
We have put in our chart the figures which Martin and Rowland 
obtained during November, 1910, to show the still further fall in the 
degree of infestation with C. agyrtes. 
July, 1911 ... 
2-31 
fleas per 
rat (154 
rats). 
August, 1911 
1-80 
») 
„ (229 
„ )• 
September, 1911 
1-32 
1 > 
„ (202 
„ )• 
October, 1911 
1-11 
»» 
„ (190 
)• 
November—December, 1910 ... 
0-5 
1 i 
o 
o 
„ )■ 
The proportion of the sexes was slightly lower for the females than 
iu C. fasciatus. There were 57 per cent, females and 43 per cent, males 
for the whole period; and for each month the same proportion, almost 
exactly, prevailed as in C. fasciatus. 
G. agyrtes apparently is a “ country ” flea, for while, in the buildings, 
only 28 per cent, of the fleas taken were of this species, in the hedge¬ 
rows 52 per cent, were C. agyrtes. Of the total number of agyrtes, 
61 per cent, came from hedgerows and 39 per cent, from buildings, being 
the reverse of what was observed in the case of G. fasciatus. Martin 
and Rowland also found a preponderance (about 60 per cent.) of G. 
agyrtes in a lot of fleas taken from rat-nests in hedgerows. 
Ceratophyllus mustelae {Pulex mustelae Dale, 1878) 
Wagner, 1898. 
We found 17 specimens of this species upon 16 rats in the following 
parishes :—Playford (2), Bentley (3), Felixstowe (3), Kesgrave (1), 
Rushraere (2), Brantham (2), Rendham (1), Assington (1), Holbrook (1), 
Tattingstone (1). 
Its common host is the weasel {Mustela vulgaris). 
