238 ECONOMIC ZOOLOGY 



food and not allow them breeding places, it is not possible always to 

 do this, and it is usually necessary to combine these preventive meas- 

 ures, with active measures for their destruction. 



Two chief destructive agents are used (besides cats, dogs, etc., to 

 be noted later): traps and poisons. There are numerous types of 

 traps on the market, many of which are effective if intelligently handled. 

 Perhaps the best traps for general purposes are the spring or guillotine 

 traps; some of these are made entirely of metal, Fig. 151, and are easily 



FIG. 151. All metal guillotine or "snap" rat trap. X/^. (From Lantz, House 



Rats and Mice.) 



deodorized by heat or water; others have a wooden base, Fig. 152, and 

 have the advantages of being somewhat cheaper and of being more 

 easily set. These traps kill the victim instantly and are so cheap that 

 they may be set by the dozen, which is obviously advantageous. They 

 can also be placed in the runways of the rats where they often catch 

 rats without being baited. They are very "quick on the trigger" 

 and it is almost impossible for a rat to remove the bait. Various sub- 

 stances should be tried for bait, usually some kind of food that is scarce 

 in the place where the trap is set; for example, where grain is about, 



