Feb. 4, 1918 Interrelations of Fruit-Fly Parasites in Hawaii 



291 



From the total of 627 puparia 143 cases are noted in which an overlapping 

 in parasitism occurred, wherein the puparia in each case contained larvae 

 of O. humilis in combination with larvae of a species of Diachasma, and 

 in 133 of these cases the former was destroyed. 



The collection of extensive data on the percentage of parasitism ex- 

 erted by the fruit-fly parasites in Hawaii over a period of three years 

 gave abundant proof that the parasite Diachasma iryoni was most active 

 during the warmer months of the year. This increase in activity and 

 abundance paralleled a reciprocal decrease in the abundance of Opius 

 humilis. The reverse was true during the remainder of the year, when 

 the former species rapidly decreased and the latter ascended to a place 

 of first importance. The data presented in Table I most positively reveal 

 the extent of fluctuation in the comparative abundance of O. humilis and 

 D. iryoni, the effectiveness of O. humilis being clearly at its maximum 

 during the spring, when the abundance of D. iryoni is at its lowest, 

 owing to the accumulated effect of the cool winter months. 



Table I. — Comparison of seasonal abundance of Optus humilis and Diachasma tryoni 



Locality. 



Honolulu, Oahu 



Do 



Do 



Do 



Do 



Do 



Do 



Do 



Do 



Do 



Do 



Do 



Kona District, Hawaii 



Do 



Do 



Do 



Do 



Do 



Percentage 

 of Opius 

 humilis. 



97. I 

 89. I 

 81.0 

 30.2 



23-5 

 22. I 



20. I 



23-3 



21. I 



38.1 

 32.6 

 66.4 



26. 4 

 56.7 



83- 9 

 80. I 



a For similar data for 1915, see Back, E. A., and Pemberton, C. K., the mediterranean fruit 

 FLY IN HAWAII. U. S. Dept. Agr. Bui. 536, 119 p., 21 pi., 24 fig. 1918. 



From September to December, 1916, a microscopical examination was 

 made of the contents of 618 fruit-fly puparia obtained about Honolulu 

 from coffee, guavas, and the winged kamani (Terminalia catappa). Of 

 this total, 55 puparia were parasitized by only Opius humilis, 331 were 

 parasitized by only Diachasma iryoni, 35 contained only larvae of D. fulla- 

 wayi, 96 contained living larvae of D. tryoni together with dead larvae of 

 O. humilis, 4 contained dead larvae of D. tryoni together with living larvae 



