MAMMALIA 245 



an introduced species from Europe. It is somewhat similar to the rats 

 in habits and owing to its small size it is able to escape from its larger 

 cousins by entering crevices too small for the rats to follow. Although 

 of so small a size it occasionally occurs in such incredible numbers 

 that it does very serious damage, as was recently the case in Australia 

 where, in the summer of 1917, enormous quantities of wheat were de- 

 stroyed by mice, which suddenly appeared and increased with unbeliev- 

 able rapidity until they swarmed about the wheat depots by the 

 million. 



Owing to inadequate shipping facilities, the wheat sacks were 

 collected in enormous piles at various places, and it was in this sacked 

 wheat that the mice collected and did such serious damage. Photo- 

 graphs were shown where, by gnawing the bottom sacks, the whole 

 pile was caused to collapse into a mass of torn bags and loose grain; 

 in one case more than 6000 sacks of wheat were "Reduced to a 

 Sickening Dump Heap by a Voracious Host." 



After trying unsuccessfully various expedients a very simple remedy 

 was worked out as follows: the stacks of bags were surrounded by a 

 double wall made of strips of corrugated iron about 2 feet wide. 

 This wall made a series of narrow, converging runways, whose narrow, 

 open ends opened over deep pits. By hanging empty sacks over the 

 outer side of the outer wall and the inner side of the inner wall the 

 mice were enabled to get into the runways in either going to or away 

 from the stack, but they could not escape from between the two strips 

 of iron and were easily driven through the narrow end of the passage 

 into the pit, where they were killed by asphyxiating gases. By this sim- 

 ple scheme the pest was brought under control. Mice were caught, 

 literally by the ton and by the million. For example it was reported 

 that approximately 500,000 mice, weighing about 8 tons, were captured 

 in four nights at one grain store. A modification of this method might 

 be used in this country where mice become particularly abundant. 



Under ordinary conditions, in houses and stores, the house mouse 

 can be exterminated by the systematic use of large numbers of traps, 

 preferably of the guillotine type shown in Fig. 152. They have not 

 the cunning of the rat so that they are much more easily trapped, using 

 the same baits mentioned above for rats. Flour is often a very 

 effective bait for mice. 



Of more serious importance to the farmer and fruit grower are the 



