Dec. 15, 1920 Opius fletcheri, Parasite of the Melon Fly in Hawaii 437 



A careful examination of 442 fruits of Momordica, collected at random 

 over an area of % square mile in the Kona district, made by C. E. Pem- 

 berton on May 8, 1916, gave the following results: 194 were not in- 

 fested, and the 248 that were contained a total of 559 eggs and 1,222 

 larvae of the melon fly. This is an average infestation per fruit for the 

 442 fruits of 4 flies either in the egg or larval stage. 



The first adults of Opius fletcheri were liberated in this district in the 

 summer of 19 16. Data secured by C. E. Pemberton during the latter 

 part of April and the first part of May, 19 18, showed that it had 

 become widely established, was parasitizing a very high percentage of the 

 melon fly developing in Momordica, and that it had so greatly reduced 

 the number of flies that cultivated cucurbits were being raised with 

 little or no infestation. Out of 1,706 Momordicas collected by him on 

 April 25 and 26, 19 18, 347 fly larvae emerged the first two days after col- 

 lection, of which 299, or 86.2 per cent, produced parasites. On April 

 28 and 29, 700 Momordicas were collected, from which 226 melon- fly 

 larvae emerged during the first two days. Of these 226 larvae 219, or 

 96.9 per cent, produced parasites. From these two lots 103 larvae 

 emerged after the first two days, making a total of 676 larvae developing 

 in 2,406 ^fruits. This is an average of less than 0.3 larva per fruit, as 

 compared with an infestation of from 4 to 6.5 larvae per fruit before the 

 liberation of O. fletcheri. 



Further observations made at the same time of 1 ,706 ripe Momordicas 

 collected in the same locality showed that only 36 of this number con- 

 tained either eggs or larvae of the fly. Thirty ripe fruits of the same 

 plant, collected at Honaunau, about 12 miles from Kealakekua, showed 

 no infestation whatever. On May 10, 1918, 400 cucumbers, both large 

 and small, 28 young watermelons, 20 young muskmelons, and 21 young 

 pumpkins were carefully examined in a garden in Kealakekua. This 

 garden was bounded on one side by a coffee plantation and on the other 

 three sides by pasture land that was overrun with heavily-fruiting vines 

 of wild Momordica. Only one cucumber was found that had been 

 punctured by the melon fly. None of the other vegetables or melons 

 that were examined had puncture scars, either new or old, and none of 

 the blossoms of any of the plants were stung. 



In June, 19 19, this same low degree of infestation still existed in this 

 district. From 890 Momordicas collected at that time the average 

 infestation was less than 0.2 larva per fruit. In several gardens less 

 than 3 per cent of the cucumbers and melons that were examined showed 

 evidences of attack, and none of the blossoms were found that had been 

 stung. 



When the vines of wild Momordica are abundant on pasture lands, 

 their ability to cover and kill large patches of grass has caused them to 

 be considered a pest, and consequently they have not been allowed to 



