1904.] 



The Pea Beetle. 



225 



Cabbages may be dusted with gas lime that has been 

 exposed to the air for three months or so : the lime runs down 

 into the cabbages and makes them obnoxious to the larvae 

 without harming the plants, though it necessarily renders them 

 less suitable for feeding or culinary purposes. 



These beetles attack peas only, although a closely allied 



species, B. ruftmanus, attacks in a simi'ar way the bean. They 



are very destructive, their presence being 



beetle.* harmful because they interfere with and 

 (Bruc/ius pisi.) . . , .'■ - 



may prevent germination, while if the 



seeds do germinate the resulting plants are often weakly. The 



beetles, moreover, fly well in sunshine, and spread to other pea 



crops for their egg laying. 



As a preventive measure, peas should not be sown which 

 contain the pest. It has been stated that the attacked peas can 

 be separated from the healthy by placing the sample of peas in 

 water, when the healthy ones sink while the infected ones float. 

 This statement is not wholly trustworthy. Jn experiments with 

 sound and attacked peas it was found that healthy sound peas 

 sink at once, but that peas with holes in them from which the 

 beetles had issued, and those with the outer skin broken but with 

 the beetle still in situ may float for a short time, but ultimately 

 they all sink. Peas with the outer skin unbroken and con- 

 taining the beetle, on the whole, continue to float. 



The best mode of killing the pest in the pea is by fumigating 

 the peas with bisulphide of carbon. The method is to enclose 

 the peas to be treated in an airtight box or chamber ; then place 

 some bisulphide of carbon in a saucer or open dish laid on the 

 top of the peas, and allow it to remain for 24 hours. One ounce 

 of bisulphide of carbon would do for every 40 cubic feet of 

 space. Bisulphide of carbon fumes are poisonous, and must 

 therefore not be breathed by the operator, nor must a light of 

 any kind be brought near. 



* An account of this beetle was given in the- Journal, Vol. II., September, 1S95, 

 p. 164. 



