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II. Research on the numher of males and females of 

 Phanurus beneficiens in Pasoeroean. 



The proportion of the number of males and females of Phanurus 

 is not always thesame; perhaps it may depend on different circum- 



stances such as the climate, the locality, the manner of cultivation 

 of the sugar cane, its harvesting, the generation of the host, the 

 reproductive condition of the parasites, the inlluences of other insects 

 or other animals, etc 



It is a very striking thing that in Pasoeroean these parasites 

 have such an important value in checking the increase of the cane 

 borer; I found these parasites about six years ago in Formosa al- 

 ready and took many investigations upon them, but always the 

 Phanurus was far less effective than Trichogramma (Trichogram- 

 matoidea nana and Trichogramma pseudonana); I cannot consult 

 here my notes about this subject, but I remember that their eifec- 

 tive power was lower than 4%. On the contrary in Pasoeroean their 

 parasitic power on Diatraea was found to be about 40%- 



The proportion of the sexual mumbers of these parasites may 

 have an inlluence on this difference of efficacy and therefore these 

 numbers were studied after the two following methods, firstly by 

 miscellaneous collection, secondly by breeding of individual eggmasses. 



With miscellaneous collection 1 mean the collecting of the pa- 

 rasites in the several breeding bottles. whereby I got the following 

 results. 



Miscellaneous collection of Phanurus. 



