OPIUS FLETCHERI AS A PARASITE OF THE MELON 



FLY IN HAWAII 



By H. F. WlLLARD 



Assistant Entomologist, Mediterranean Fruit-Fly Investigations, Bureau of Entomology, 



United States Department of Agriculture x 



INTRODUCTION 



The braconid parasite Opius fletcheri Silvestri was introduced into the 

 Hawaiian islands from India in May, 1916, by D. T. Fullaway, represent- 

 ing the Board of Commissioners of Agriculture and Forestry of the 

 Territory of Hawaii. It was brought in as a parasite of the melon fly 

 (Bactrocera cucurbitae Coquillett) which had been causing great losses 

 to the vegetable growers of the islands. The only host here which it 

 attacks freely under field conditions is the melon fly, although it can be 

 bred freely in the laboratory from the Mediterranean fruit fly (Ceratitis 

 capitata Wiedemann). From many thousands of Mediterranean fruit- 

 fly puparia, secured from fruits collected in the field, only four adult 

 O. fletcheri have been reared. One was bred from fruit-fly larvae devel- 

 oping in fruits of Chrysophyllum oliviformae, one from larvae in fruits of 

 tropical almond (Terminalia catappa), and two from larvae secured from 

 coffee (Coffea arabica). The first two were collected in Honolulu, and 

 the last two were from the Kona district of the island of Hawaii. 



A clear conception of the biology of this parasite and a record of its 



activities since its introduction into Hawaii are the two principal objects 



of this paper. 



DESCRIPTION AND LIFE HISTORY 



EGG 



The egg is always deposited in the larva of the host, just beneath the 

 skin. Its pointed, attenuated end becomes firmly glued to the inner 

 surface of the larval integument by a dark, almost black substance; 

 and its free end projects obliquely into the body cavity of the larva. 

 The spot receiving the egg soon becomes darkened; and the dark sub- 

 stance by which the egg is attached to the host larva may be a darkened 

 clot of larval fluids which originally exuded when the wound was made 

 by the insertion of the ovipositor. 



Immediately after deposition (fig. 1) the egg is cylindrical, bluntly 

 pointed at both ends, slightly more convex dorsally than it is concave 

 ventrally, and translucent white with a smooth, glistening surface. Its 

 average length is 0.54 mm. and it is about one-sixth as broad as long. 

 Just before hatching (fig. 2), its width is a little over one-third the length, 



I Credit is due C E. Pemberton, formerly with the Bureau of Entomology, for the drawings contained 

 in this paper and for the greater part of the microscopic work performed during its preparation. 



Journal of Agricultural Research, Vo1 - xx - No - 6 



Washington, D. C *>ec. '*• ^ 2 ° 



wa Key No. K-88 



(423) 



