FORMS INJURIOUS TO HUMAN INDUSTRIES 



359 



particular preventive measure chiefly applies to insectivorous birds 

 and mammals. 



(2.) Curative Meastires. — It is possible to collect and destroy 

 many sorts of pest (see p. 353), although this is usually an ex- 

 pensive matter. The question as to which stage in the life-history 

 of a particular form most readily lends itself to the method is 

 clearly one of great economic importance. 



Collection is sometimes facilitated by " luring " pests by means 

 of something which serves to attract them. Slices of potato, for 

 example, have been found to draw large numbers of wire-worms. 



Fig. 1256. — Winter-Moth {Chewtatobia byitmata) male (centre), female (right), and chrysalis (left). 

 The vertical lines indicate actual sizes. 



Many creatures can be destroyed in the places where they live 

 by means of certain powders and sprays, distributed by various 

 ingenious appliances. Soot, quick-lime, " Paris green " (an aceto- 

 arsenite of copper), soap-suds, paraffin emulsion, &c. &c., all have 

 their special uses. 



(3.) Measures ivhich are both Preventive and Curative. — These 

 may be illustrated by "tar-rings", employed in combating the 

 Winter- Moth [Cheimatobia brttmata, fig. 1256), destructive to 

 fruit-trees, and the Gipsy-Moth (Ocneria dispar), which is an 

 enemy to all sorts of trees. In both these species the dormant 

 chrysalis stage is passed through in the ground. As the wings 

 of the female Winter- Moth are small and useless, while the female 

 Gipsy-Moth cannot (or at any rate does not) fly, both of them 

 have to creep up the tree-trunks in order to lay their eggs. This 

 can be prevented by means of a tar-coated band of suitable 

 material fixed round the trees a short distance above the ground. 

 Collection and destruction of moths and eggs naturally follow. 



