438 Journal of Agricultural Research voi.xx.No. e 



become abundant in many localities in Hawaii. When Momordica is 

 abundant and Opius fletcheri is present, it has proved of considerable 

 value as a trap plant for the melon fly. Infestation records made before 

 the parasite was liberated show that Momordica is much favored as a 

 host by the melon fly, while subsequent records of parasitism show that 

 its size and texture permit the parasite to kill about 90 per cent of the 

 larvae developing in its fruits. Whether or not it would be of advantage 

 to plant these vines around vegetable gardens as a catch plant is a 

 problem open to further investigation. 



Opius fletcheri, besides becoming firmly established on all the larger 

 islands of the group, has shown itself capable of reducing the number of 

 melon flies by at least 25 per cent, even when the host larvae are devel- 

 oping in fruits the size and nature of which make parasitism difficult. 

 In a location where the fruits and conditions are most favorable to its 

 reproduction it has reduced the flies so greatly that they have almost 

 ceased to be a pest. While O. fletcheri is far from being able to control 

 the melon fly in Hawaii completely, the benefits derived from its activ- 

 ities since its establishment there have been sufficient to warrant the 

 efforts connected with its introduction. 



