No. 2.] Reprints and Extracts. 57 



4. Click Beetles and Wireworms. FAM. ELATER1DM. 



Effect on Wireworms of Castor-oil seed-cake, Rape-cake, and also of absence of 



food. 



"The following details of experiments, carried on during a period of three 

 months by Dr. Bernard Dyer (Laboratory, 17 Great Tower Street, London, 

 E. C.) relatively to effect of Castor-oil seed-cake and Rape-cake on wireworms, 

 was kindly placed by him in my hands, with the remark (Nov. 14th, 1898) :— 



" I have been trying if cotton-oil cake (very deadly to mammals) would kill 

 wireworms. The experiment is a very rough one. Enclosed is a description of 

 what happened: — 



" Description of experiments on wireworms.- — One hundred worms were placed 

 in each of three jars of earth and fed, respectively, with Castor-oil seed-cake, 

 with Rape-cake, and with nothing. The cake was given in great abundance, 

 in both cases, being applied as fast as the worms seemed to dispose of it, 

 that is to say, as fast as ,it disappeared, though the disappearance may 

 not have been entirely due to its consumption as food, but partially to 

 decomposition. 



" By the end of two months about a third of an ounce of cake had been supplied 

 to each jar. The soil in each case only weighed about ten ounces, and the 

 cake applied must have been at the rate of far more than one hundred tons per 

 acre ; so that the experiment, even if an exaggerated one, seemed well calculated 

 to show whether there might be any specific difference in the effects of the food 

 supplied. The earth was of course kept equally moist in all three cases, 



' At the end of three months the pots were turned out, and it was found 

 that, of the hundred worms which had had no food at all in addition to the earth 

 in which they lived, ninety-eight were alive, though their condition was very 

 meagre; of the hundred worms supplied with castor-oil seed-cake, ninety-three 

 were alive and in good condition ; of the hundred, however, that had been fed upon 

 ground Rape^cake only six were alive. 



'It would appear, therefore, that Rape-cake when supplied in such 

 superabundance as in this experiment, brought about a large destruction of the 

 worms, though it does not by any means necessarily follow that it would do 

 when used on the small scale adopted in actual farming. On the other hand, it 

 seems to be abundantly clear that Castor-oil seed-cake, although it is virulently 

 poisonous to higher animals, fails to excercise any poisonous effect upon wire- 

 worms, which are apparently indifferent to its acrid poison. 



' Still more cake was given, but this cake, the weather being warmer, decom- 

 posed, and the soil became infested with smaller life, which seems to have brought 

 about conditions uncongenial to the wireworms ; and it may be also that the 

 effects of crowding for so long a time without change of soil were bad for 

 them ; for first the cake-fed ones died ; and then those without food.' 



" The foregoing observations need no comment beyond Dr. Dyer's own remarks 

 as to the presumable cause of the ultimate death of the wireworms after the period 

 of three months had expired, of which notes are given. But two of the special 

 points recorded well deserve attention ; one of these is the observation that wire- 

 worms can exist (although they did not thrive) for three months upon an almost 

 infinitesimal amount of food, a fact which may be utilised for field work, as 



