October, 15] SWEZEY: INSECTS IN THE HAWAIIAN ISLANDS 



455 



Cane Borer Tachinid 



Another remarkably successful parasite introduction was a tachinid 

 {Ceromasia sphenophori) parasitic on the sugar cane weevil borer ' 

 {Rhahdocnemis ohscura). This was brought from New Guinea by Mr. 

 F. Muir in 1910. An account of his search for parasites for the cane 

 borer, the finding of this tachinid and its introduction to Hawaii are 

 given in the Journal of Economic Entomology, Vol. VII, page 455, 

 1914. Within two years the tachinids had been distributed to nearly 

 all plantations and well established in many of them. Nearly five 

 years have now elapsed and the beneficial results are very apparent. 

 Already, in 1913, the tachinids had become sufficiently abundant to 

 cause a considerable reduction in the number of borers in the cane, and 

 a consequent diminution of damaged cane resulting in an increased 

 yield of sound cane per acre. This was especially noticeable in those 

 plantations where the pest had been the worst, and where on this ac- 

 count efforts to establish the tachinids had been concentrated at the 

 outset. On one of these plantations where the manager was keeping 

 definite records, and the usual infestation by borers was 30 per cent 

 of the canes, it had dropped to an infestation of only 12.77 per cent. 

 This has resulted in a greater yield of good cane per acre, and at the 

 same time the quality of the juice in the cane has been so much im- 

 proved that more sugar is produced per ton of cane. To use figures 

 from the plantation reports: it now requires 1.67 tons less of cane to 

 produce one ton of sugar than it did formerly. 



Another plantation, that has been similarly benefited, reports that 

 its yields have been increased by a little over two tons of sugar per 

 acre. If the price of sugar be taken at an average of $75 per ton, this 

 would mean a saving of $150 per acre, and the plantation harvesting 

 1,000 acres annually would have a saving of $150,000. 



Not all plantations have been benefited to the extent of these used 

 as illustrations, for not many were so severely infested by borers as 

 these were, but many have been very considerably benefited. The 

 total saving to the sugar industry of the Islands would amount to many 

 thousands of dollars annually. It is significant that the crop of sugar 

 in 1914 was 21,780 tons greater than any previous crop in the history 

 of the sugar industry in the Hawaiian Islands. 



Present conditions indicate that the tachinids have reached their 

 maximum efficiency, for they are now less abundant in the fields than 

 they were shortly after the time when they became generally spread. 

 This is by reason of the reduction in the number of borers. Where 

 the borers were formerly most numerous, it gave the tachinids oppor- 



