434 



Journal of Agricultural Research 



Vol. XX, No. 6 



available host larvae from the time of emergence. Two of these began 

 ovipositing in 2 days, one in 3, three in 5, and two in 7 and 9 days, 

 respectively. None of these females oviposited after they were 30 days 

 old, excepting one, which deposited one egg at the age of 33 days. The 

 majority of eggs are deposited within the first 3 weeks after oviposition 

 begins. As noted before, females that have had daily opportunity to 

 oviposit do not live so long as those that have had no opportunity; but 

 they frequently live from 4 to 5 weeks after oviposition has ceased. 



IMPORTANCE AS A PARASITE 



Opius fletcheri, in the three years since its introduction into the 

 Hawaiian Islands, has become firmly established on all the large islands 

 of the group. While this parasite alone will never exercise a complete 

 control over the melon fly in Hawaii, it has already proved of much value 

 by decreasing the numbers of this pest considerably. Good examples of 

 the most abundant melon-fly host plants are cucumber, squash, pump- 

 kin, and watermelon. The fruits of these plants are large and fleshy, 

 and melon-fly larvae that develop in them feed so far from the surface 

 that a larval parasite, such as O. fletcheri, that oviposits entirely from 

 the outside, finds it impossible to parasitize enough of the larvae to exert 

 a control over the pest. 



Table I gives data showing the extent of parasitism by Opius fletcheri 

 of melon-fly larvae developing in cucumbers collected in and about 

 Honolulu during the last eight months of 191 8 and the first eight months 

 of 1 91 9. 



Table L- 



-Percentage of parasitism by Opius fletcheri of larvce of Bactrocera cucurbitae 

 in cucumbers 



Month of collection. 



Number of larvae 

 emerging during 

 first two to four 

 days. 



1918 



Percentage of parasit- 

 ism. 



1918 



January. . 

 February. 

 March. .. . 



April 



May 1,014 



June 2, 719 



July 2,052 



August 43 1 



September 3, 594 



October 2, 516 



November 8, 282 



December ' 4, 319 



1,031 



539 

 6, 442 



3,i9 2 

 1,481 



1,318 



5.255 



19. 3 21 



5-9 

 10. o 



21. 9 

 21.8 

 29. 8 

 16.6 



22. 1 

 7-3 



2.9 



14-5 

 9.0 



2. 2 



6.4 



10. 6 



7-3 



The highest percentage of parasitism existed in September, 191 8, 

 when 1,070 out of 3,594 melon-fly larvae under observation were parasit- 

 ized. This shows a parasitism of 29.8 per cent, while the parasitism 



