THE AUSTRALIAN MUSEUM MAGAZINE. 



115 



of the underworld, it is the rat of sewers 

 and basaments. The black rat on the 

 other hand prefers the upper stories and 

 roofs, and has ©ven in places taken on 

 a more or less arboreal existence. It is 

 also the ship rat, though both species 

 may be so carried. 



The rat is a voracious eater and catho- 

 lic in its tastes; nothing that is in the 

 remotest sense eatable comes amiss to a 

 rat, though probably by nature they are 

 -grain feeding. The life history of the 

 two species is similar. In Sydney both 

 species probably breed all the yeai- 

 round, though there are no data avail- 

 able to calculate the number of litters a 

 rat may have in one year. It is known, 

 however, that these animals breed at an 

 early stag( , and litters follow one an- 

 other at intervals of weeks. The num- 

 ber per litter varies, but in Sydney the 

 average per litter for B. norveg-icus is 

 8.05 and for R. rattus 6.66. 



It has been said that both species art- 

 spread all over the world. Though in 

 the main correct, this statement recjuires 

 qualification, as the two species are at 

 the present day not equally distributed; 

 in general it may be stated that the 

 brown rat is the rat of the temperate 

 zones and the black rat that of the 

 tropics. Probably both species origin- 

 ated somewhere in central Asia and be- 

 came habituated to their present mode 

 of life in and around the tents of the 

 nomadic Tartar tribes with whom they 

 lived. This is in . the main pure specu- 

 lation, but there is definite historical evi- 

 dence of the time of their invasion into 

 Western Europe. The black rat camt= 

 first, arriving in England somewhere 

 about the twelfth century, and is said 

 to have been brought back by the Crus- 

 aders. The advent of the brown rat into 

 England is comparatively recent, these 

 rodents making their appearance during 

 the time of George T. They are sup- 

 posed to have come to England in ships. 

 In England, as elsewhere on the con- 

 tinent, they rapidly displaced the black 

 rat, which, however, at the present time 

 i.s re-app«ajing in the big seaport towns. 

 In the tropics the black rat has held its 

 own, while in subtropical centres as at 



Sydney, both species are represented in 

 approximately equal numbers. 



Both species suffer from plague, but 

 in most of the tropical countries where 

 plague is endemic to-day, the black rat 

 is the reservoir. Other animals also 



Indian Red Flea (Xenopsylla cheopis). 

 Photo. — K. Grrant. 



suffer from plague, for example, the 

 Califomian ground squirrel and the Tar- 

 bagan or Mongolian marmot ( {Arctomy» 

 bohac), which w^as held to be primarily 

 responsible for the calamitous Man- 

 churian pneumonic outbreak in 1910. 



Eleven different species of fleas havb 

 been shown to be capable of carrying 

 plagTie. Most of these, however, are 

 only of local interest or else do not 

 readily bite man. Two ai'e, hoAvever, 

 especially inculpated; these are the In- 

 dian Red Flea {Xenopsylla cheopis) 

 which is the rat flea of the tropics, and 



European Rat Flea (Ceratophyllus fasciatus). 

 Photo. — K. Grant. 



