8 
Ohservations on British Rat-fleas 
(I) The great majority beloaged to two species only. The following 
table shows the numbers of each species found : 
Xo. collected 
1. 
Ceratophyllus fasciatus 
1986 
2. 
Ctenophthalinus agijrtes 
12-57 
3. 
Ceratophyllus mustelae^ 
17 
4. 
C. ivalkerO ... 
8 
5. 
Archueopsylla erinaceO 
7 
6. 
Ctenophthalmus pentacanthus^ ... 
3 
7. 
Ctenopsylla muscuU 
3 
8. 
Piile.v irritans 
2 
9. 
Ilystrichopsylla talpae 
2 
10. 
Gtenocephalus cams 
2 
11. 
Ctenophthalmus bisoctodeutatus^ 
2 
12. 
Ceratophyllus gallinae^ 
1 
13. 
C. hirundinis^ (?) 
1 
14. 
Palaeopsylla sorecis^ ... 
1 
15. 
P. minor 
1 
3293 
(II) Ohservations made on the various species of fleas found on rats. 
Ceratophyllus fasciatus {Pulex fasciatus Bose d’Antic, 1801), 
Hilger, 1899. 
The number of this species found on grown-up rats recently killed 
was 1986 from 822 rats—an average of 2’42 per rat. 
Besides this, about 70 per cent, of the fleas caught on “nestling” 
rats were of this species, while of the fleas taken from rats found dead, 
either of injury or disease, about 90 per cent, were C. fasciatus. It 
would appear from this that G. fasciatus deserts a dead rat later than 
do other species. One of the dead rats was picked up in a yard in 
Avhich many others lay dead, one of which was subsequently found to 
have had plague ; this rat was infested by 37 fleas, although it was 
quite cold. 
In the various districts mentioned in the table we could find no 
correlation between the sporadic cases of rat plague and the average 
number of C. fasciatus per rat. In view of the fact that this species 
bites man, we will here give the average number collected in each 
district. 
1 Found on Mus decumanus for the first time. Rothschild (1910) does not record 
CcratophnUun mustelae, although Tiraboschi (1904) does so. We have accepted Roth¬ 
schild’s authority in this matter. 
