October, '14] ILLINGWORTH: TACHINID PARASITES 393 



in moving about, quickly reached the opening and disappeared. The 

 fly paid no attention to the larvae after depositing them on the cane. 

 In a number of other observations the flies were proved to have first 

 located the borer grub, positively, near the pin-hole before depositing 

 the maggot. This was done, in several instances, by cutting into the 

 cane and finding it just inside the spot. 



In one case a grub was removed in half an hour after the larvae 

 entered the pin-hole, and they were later found to be inside of him. 

 Hence, they lose no time in boring their way into the living grub. 



Continued Supply of Cane and Grubs 



Another discovery that proved of great value to the breeding work 

 was made while rearing the first brood of flies. A fresh quantity of 

 cane containing borers was added to one of the cages, when the flies 

 were 16 days old. Evidently they had pretty well gone over most of 

 the borers already in the cage; at any rate, as soon as the fresh borers 

 were introduced, they left the old canes and all congregated about 

 the new ones. One might conclude that they were after the fresh 

 supply of sugar, but this did not appear to be the case, for they became 

 very active in their search for the pin-holes of the borers. This dis- 

 covery indicated plainly that the flies must have a continued supply 

 of fresh grubs if they are to give their maximum returns in breeding 

 work. Our later results, when this was carried out, proved most grati- 

 fying. 



Observations of the second brood gave us further information as to 

 the time that must elapse after the flies emerge before larva-positing 

 begins. In the case of the flies that copulated during the flrst day, 

 they were seen intently examining the pin-holes of the borer when only 

 two days old, and one was seen larva-positing on the third day. 



♦Some of the flies in our cages remained alive and actively larva- 

 positing through the entire period of six weeks, which is the ordinary 

 time required for a generation to develop. 



Light Relation 



Most insects show a decided attraction to light, only a few seeking 

 dark places. These Tachinid flies from their habit of living in the cane 

 field, we would conclude, should have all degrees of light and shade. 



In experiments in Honolulu it was soon learned that they were not 

 contented in cages that were too dark, and refused to larva-posit. The 

 same thing was partially true when the cages were provided with no 

 shade. In our experiments on this point, in Fiji, we tried to supply 

 as nearly field conditions as possible. In the cage that was so ar- 

 ranged we got our best results. This cage had a few leafy stalks of 



