208 PROTECTION AGAINST INSECTS. 



as a protective belt, and border trees generally, should be first 

 shaken, as the chafers collect there. 



The larvae and beetles may be killed by : 



Crushing on hard ground. 



Scalding with hot water, which gives rise to an extremely 

 unpleasant odour. 



Immersion in casks containing a mixture of water and 

 petroleum, or 2 per cent, of naphthalin. Both larvae and 

 beetles live for some time in water alone. 



Burial in layers in a trench with unslaked lime, or powdered 

 calcium chloride. 



Subjecting the insects to fumes of bisulphide of carbon. 

 This is the best method of destroying them, and was first 

 discovered by Dr. A. Mayer. When done on a large scale, 

 a clean empty petroleum cylinder or similar vessel may be 

 used, in which the carbon bisulphide is poured on the 

 insects. 



In order that the gas may have its full effect, the tin should 

 be covered with a sack, or woollen cloth, to keep out the air. 

 Lights and fire must be kept at a distance during the opera- 

 tion. A bushel of cockchafers may be killed by less than an 

 ounce of carbon bisulphide, and the insects die in from 5 

 to 10 minutes. 



Where cockchafers are extremely abundant and injurious, 

 as in Germany and France, the expense of collecting them 

 is so serious, that it is lightened as much as possible by 

 the utilisation of the captured beetles. 



This is done in three ways : They are used as food for swine, 

 fowls or geese, being mixed with three or four times their 

 weight of potatoes or starchy material ; for the extraction of 

 a coarse oil suitable for cart grease ; or for manure, being 

 mixed with earth, bone dust, or stable-manure. 



Their value as a food-stuff is about Is. per 10 Ibs. ; as a 

 manure, about 9d. per 10 Ibs. 



vi. A plague of cockchafers, like a plague of mice, being 

 felt by agriculturists and fruit-producers, as well as foresters, 

 must be met by energetic common action of all municipalities 

 and village authorities, and in case the interested parties 

 cannot agree as to any common course of action, the State 



