FALSE PARASITES. 109 



each segment lining the shields with a brownish-red and' delicate 

 border, and which is velvet-like, very fine, lustrous, and soft, and 

 which can be loosened and shaken away at the caterpillar's 

 pleasure, be merely a mechanical or also at the same time a 

 chemical irritant; opinions differ somewhat. Miiller and 

 Rabenhorst found a peculiar acid and a volatile oil on examining 

 chemically the fir-weevil (Eombyx Pini) which offers similar con- 

 ditions, without, however, experiencing any noxious effects from 

 the oil or the acid. Ratzeburg believes that a poisonous volatile 

 principle exists (analogous, perhaps, to the poisonous principle, 

 of sumach, and other poisonous plants) which is simultaneously 

 developed with the dust. 



Treatment and Prophylaxis. The destruction of the caterpillars 

 by burning and singeing them by means of wisps of straw or by 

 sweeping them off the trunks of the trees and crushing them on 

 the ground, is always dangerous to the operator, since the dust 

 is dispersed in the air. Obstacles to their migration, such as 

 coal-tar, tarred paper, and digging trenches round the trees, are 

 of no avail, as the caterpillar simply goes round them, and crosses 

 even small brooks. I think it would be best to discover the 

 nests and wrap them up with rags soaked in oil, and then to cut 

 away the branch and to burn or bury it. It would be well, 

 however, to destroy the insect in the chrysalis state towards the 

 end of July or middle of August, before the butterfly creeps out, 

 in order to restrict its propagation, or to hunt up and annihilate 

 the latest brood which exists before the second casting of the 

 skin without the dangerous dust. It would, therefore, be necessary 

 to search from the beginning of May to the beginning of June 

 for the wandering troops. The collector of nests and caterpillars 

 will do well to use a blunt hoe, to wear gloves, and to oil the 

 skin. There are generally only one or two nests in each tree. 

 The caterpillar has but few enemies in the animal kingdom, of 

 which I may mention the ichneumon. Birds seem to be afraid 

 of it. Precautions ought to be taken to prevent persons entering 

 infected forests by means of notices, by the digging of ditches, 

 &c. The pasturing of animals in such forests and the gathering 

 of fodder and litter should be forbidden. The gathering of fruits 

 of any kind should be unconditionally interdicted, and, in case 

 nests are discovered when oaks or pines are cut down, they should 

 be carefully removed, as mentioned above, without hewing them 



