MONTHLY NOTES ON GEUBS AND OTHER CANE PESTS. 21 



"It is amusing- to witness the tactics adopted by females of Dielis 

 and Campsomeris whilst overpowering their hosts. The wasp warily 

 approaches the powerful jaws of its intended victim by clinging to its 

 body and crawling with erratic movements until encountering the legs 

 of the alarmed grub, which, evidently aware of the impending danger, 

 keeps squirming and pawing the air, threatening its enemy at the same 

 time with widely opened mandibles. 



"A few seconds are passed in this preliminary fencing, and then 

 the wasp, making a sudden dive forward, seizes with caliper-shaped jaws 

 one of the mandibles of the grub, and without loss of time drives its 

 paralyzing sting deeply into the throat of the unfortunate creature. The 

 effect is almost instantaneous, the rigidly convulsive body becoming limp 

 and unable to offer further resistance, as the parasite now withdrawing 

 its sting plunges it deliberately several times into the mouth of its victim 

 between the maxilla?, in order, presumably, to paralyse the mandibles. 



"Each detail of this little tragedy in insect life can be plainly 

 witnessed with the aid of a small magnifying glass, the grub and wasp 

 being confined for convenience under a tumbler upon a piece of glass or 

 on the soil. 



"Sometimes, however, the tables are turned, and the venturesome 

 parasite is seized and fatally crushed in the sharp jaws of its adversary, 

 in which case it appears that the victorious grub does not rest until it 

 has cut the wasp into little pieces. 



"Under normal conditions the parasite, of course, burrows several 

 inches into the ground before reaching a suitable host, but in one of our 

 series of experiments it was seen that a digger-wasp when allowed to 

 paralyze a grub lying on the surface was able to undermine and bury 

 the body out of sight in less than twenty minutes. When examined next 

 day we found the grub had been transported through the soil to a 

 distance of 10 inches in a vertical direction, and was lying on its back 

 with an egg glued to the ventral surface of its body." 



* CANE GRUB INVESTIGATION, APRIL, 1918. 



"Investigations regarding the influence of cultural methods on the 

 cane-grub problem look promising on the whole, although at present it 

 is rather early to make definite statements in this connection. Such 

 operations, however, as scarifying or ploughing deeply enough to destroy 

 egg-chambers of the beetle and to occasion mechanical injuries to the 

 young grubs or expose them to great solar heat and to the attacks of 

 birds and other enemies, cannot fail to be beneficial. We are inclined 



* Written from an outline prepared by Dr. Illingworth when leaving for the 

 hospital. The few obvious mistakes are corrected in the May report. 



