Nov. 25, 1918 Biology of Fruit-Fly Parasites in Hawaii 



447 



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humid conditions. Of 2,232 fruit-fly puparia collected in the Kona 

 coffee district of the island of Hawaii in 191 7, 2 per cent were parasi- 

 tized by D. fullawayi and the percentage of parasitism here, where the 

 precipitation averages about 50 inches a year, was about the same in 191 6. 

 On the opposite side of the island, about the town of Hilo, where the pre- 

 cipitation averaged 200 inches during 191 6, parasitism by this species 

 reached 60 per cent, as determined from 316 fruit -fly puparia collected 

 from coffee. During 191 7 an unprecedented drought was experienced on 

 the Hilo side of the island and parasitism by D. fullawayi was reduced to a 

 fraction of i per cent. From 700 fruit-fly puparia secured from that source 

 during November, 191 7, at the time of the drought, no individuals of D. 

 fullawayi were reared, although the other opiines were abundant, particu- 

 larly Opius humilis. 

 Fifteen miles from Hilo, 

 however, in a locality 

 more elevated and for- 

 ested, where the humid- 

 ity can not get very low, 

 the parasitism by D. 

 fullawayi was 98.2 per 

 cent, as determined 

 from a collection of 259 

 fruit-fly puparia se- 

 cured from coffee on 

 the same date as that 

 on which the Hilo col- 

 lection was made. Per- 

 haps the most signifi- 

 cant evidence that can 

 be given to bear out this 

 point is the parasitism 

 by this species during 

 1 91 7 in upper Manoa Valley in Honolulu and at the Maunawili Ranch, 

 Oahu. At these two localities the precipitation averages 150 inches a 

 year and at Maunawili the Weather Bureau records show an average of 

 324 rainy days a year. From 78 fruit-fly puparia collected at Maunawili 

 during 1 91 6 the parasitism by D. fullawayi was 65.3 per cent. From 

 1,542 puparia secured at that place in 191 7 the parasitism by this species 

 was 88.4 per cent. From 474 puparia secured from coffee in upper 

 Manoa Valley in 191 7 the parasitism by D. fullawayi was 91 per cent. 

 Honolulu, on Oahu, has a precipitation closely paralleling that of the 

 Kona district on the island of Hawaii, usually averaging 50 inches a year. 

 In Honolulu the average collections of fruit produce fruit-fly larv^ae only 

 slightly parasitized by D. fullawayi, even though upper Manoa Valley is 

 only a few miles removed from Honolulu. Still the difference in rain- 

 fall is great between the two localities. 



Fig. 29.- 



Diachasma fullawayi: Mandible of mature larva. Length 

 0.12 111111. 



