20 MONTHLY NOTES ON GKUBS AND OTHER CANE PESTS. 



entomologists in the search for parasites in tropical countries reads like- 

 a romance; but they have been crowned with success in almost every 

 instance. 



An island fauna, however, is very different from that of a continent, 

 and it is very difficult to duplicate those results under our conditions. 

 Though we have several parasites on the grubs, their work is largely 

 neutralized by seeondarj^ parasites. 



However, there is a chance that if we brought in new parasites from 

 other canegrowing countries they might serve as an effective control, 

 and escape the attention of these secondary enemies. It is certainly an 

 experiment worth trying, and we are making investigation of the matter. 



Insect Enemies op Cane Grubs. 



"Investigations with regard to the life-history and habits of our 

 digger-wasp parasites continue to furnish data of scientific interest ; and 

 throughout the month of February adult specimens of Dielis formosus 

 and Campsomeris raclula have been emerging from pupae derived from 

 eggs laid in the Insectary during December and January last. New 

 experiments, just started (March), wall deal more fully with the ques- 

 tion of partheno genesis, and also include preliminary studies in hyper- 

 parasitism. As previously pointed out by this Office ('Australian 

 Sugar Journal,' Vol. VI., p. 583), a large species of bee-fly (Bomby- 

 lidaj) is hyperparasitic on the larva? of our digger-wasps, and apparently 

 destroys a large percentage of these useful parasites. Little or nothing 

 is yet known about the life-cycle and habits of this fly, or with regard 

 to the economy of a Rhipiphorid beetle that we have found on several 

 occasions infesting the cocoons of Scolia wasps. Experiments, too, have 

 been initiated with a view to determining the best method of breeding the 

 above-mentioned useful parasites on an extensive scale for possible 

 distribution at some future date. 



"In our last report it was stated that Campsomeris radula would 

 commence oviposition four days subsequent to emergence, but in the 

 solitary case then mentioned the wasp had been kept and fed for four 

 days in a cage without a grub. Recent data, however, have demonstrated 

 that unfertilised females of both radula and formosus will actually 

 deposit eggs upon third-stage grubs of our gre.y-back beetle within a 

 period of from twelve to fifteen hours after leaving the cocoon. 



"Such action, indeed, appears usual in the case of confined speci- 

 mens, and will probably prove to be a normal procedure in the field. In 

 this connection it may be mentioned that owing to a mistake in the 

 manuscript of our last report the word 'wasp' was inserted in place of 

 larva}; the remai'k in question slumld therefore read 'and that such 

 imfcrtilised ova hatch in a normal manner and produce larva? of both 

 sexes. ' 



