48 THE SUGAR-BEET WIREWORM. 



than 0.1 per cent were affected by it in the field. These two checks 

 are of very little importance. 



Enemies and Checks to the Larv^, 



Two characteristics of the wireworms, their thick skins and their 

 underground life, cause them to be ahnost free from enemies. Of the 

 10,000 larvse collected not one was noticed which was attacked by an 

 internal parasite, idthough such parasites have been reported attack- 

 ing Elaterichie. Curtis ^ reports an ichneumon parasite on wireworms 

 in Great Britain, and says that Bierkander (of Sweden) also found 

 them. Dr. S. A. Forbes ^ reports a single instance where a parasitic 

 fly was reared from a wireworm. Very probably there are no efficient 

 parasites in this group. 



The sugar-beet wireworm is, however, eaten readily by several 

 kinds of birds whenever exposed. During the spring, when several 

 of the fields at Dominguez, Cal. (G miles from the ocean), were being 

 plowed, it was noted that sea gulls (Larus sp.) were very abundant 

 in the fields and followed the plow much as chickens do. They 

 occurred by the hundreds and, as they are known to be omnivorous, 

 they must have eaten numbers of wireworms. At this time and 

 carUer crows were also very abundant in the beet fields. During 

 this period the wireworms were feeding at the surface on the left- 

 over beets, and it was easy for the crows to reach them. As crows 

 are famed as wireworm destroyers it is only reasonable to suppose 

 that they killed large numbers of the larvae. This point will be 

 investigated thoroughly in the future work on this insect. 



Larvte of a large carabid, probably Calosoma cancellatum Esch., 

 have been found in the ground together with injured wireworms. 



In addition to bird and insect enemies one fungous and two bacte- 

 rial diseases have been noted on this wdreworm. The fungus is only 

 observed occasionally in the field, hence it is probably of little impor- 

 tance economically. The bacterial disease of the mature larva was 

 especially disappointing, as it seemed to work only in certain cages. 

 This naturally led to the behef that its presence was probably more 

 tho result of unfavorable conditions than the cause of them. The 

 bacterial disease of the young larva did not promise much, as it did 

 not seem to attack mature larvje under any conditions. 



As has been mentioned under the heading ''Rearing cages used" 

 (p. 21), many of the young wireworms which were kept in petri dishes 

 diiul of a bacterial disease. This disease spread very rapidly, and 

 there seemed no way to check it. Wherever it appeared, all the 

 healthy wireworms were removed to a sterile cage and the infected 

 cage sterilized. The cages were examined several times a day and all 



1 Farm Insects. By John ("urtis, IStiO, pp. 181. 2 18th Rept. State Ent. 111., pp. 47, 1891-92. 



