PRESIDENTIAL ADDRESS. 105 
Pulex irritans. 
MOE ies Meyer). Vibe hss ade IW tamed ead Ws aaleettiton’s |i aoe, Was T penaely hE 
1220) Sat a eee shee the al dete eee | een mee aoe 
LOBE it, LR Pray, SUA ARYA eee RNS SS aa 9 late PY EAE eh 1 
19126 ... : 
1913 
eee: Loe lie RY eal Oy lated Lay White hE Sash d eoaebl Ata a bene 
LPL 1 NIP Se Re eV Petites Heweas (fate lg oie (era aaa | 
wee LP ge TEES eS ea a Ferry ence ea la On Tem he | 
Moatal |... l TF, ieee SP CIEE Pea me lie act Clie aoe Pee 3a 
are the months in which epidemics have most frequently 
originated and in which the majority of cases have occurred. 
Yet these figures have been obtained when, except for the 
years 1909 and 1910, no instances of plague in man or rats 
were known. The figures for the other months, though 
irregularly variable, are much lower. 
The monthly numbers of the blind flea, Ctenopsylla 
(Typhlopsylla) muscult, are less variable. Considerable 
increases occur in September and October, and next to these 
in August. 
The figures for Ceratophyllus fasciatus are smaller and 
very variable. There is a distinct increase in September 
and October, and another in December and January. 
Ctenocephalus canis or felis, of which few specimens were 
obtained, shows a preference for the warmer months. 
A further table (Table VI) shows the numbers and 
species of fleas found in Sydney in each of the three rodents 
concerned during the non-plague period 1911 to 1917. In 
E. rattus, somewhat Jess than half of 3221 fleas were L. 
cheopis, between one-third and one-half were C. musculi, 
about one-seventh C. fasciatus, a few were C. canis or felis, 
and 1 P. irritans. Five fleas found on this species from 
Goulburn, in April, 1918, all belonged to C. muscult. In E. 
norvegicus more than one-half of 2137 fleas were P. cheop- 
is, nearly one-third C. musculi, and about one-eighth C. 
