Dec. 15, 1920 Opius fletcheri, Parasite of the Melon Fly in Hawaii 433 



nean fruit fly, D. tryoni and O. humilis, that were reared from material 

 collected in the field, produced 37.6 per cent and 43.5 per cent females, 

 respectively. Since the females are responsible for all the parasitism of 

 the host, the ability of 0. fletcheri to produce so many more females than 

 males greatly enhances its value as an enemy of the melon fly. 



The longevity of the adult depends largely upon the conditions under 

 which it lives and may extend from a few days to 16 weeks. When con- 

 fined without food it will not live much over 5 days. Of 6 males and 17 

 females that were confined in a glass tube without food, 3 females died 

 before they were 3 days old, and 3 more lived to be a few hours over 5 

 days old, but the majority of both males and females died between the 

 ages of 3% and 4 days. The life of females that have had continual 

 access to host larvae is much shorter than that of those which have had 

 no opportunity to oviposit; and the life of males is considerably shorter 

 than that of the females. Of 9 females that were allowed to oviposit at 

 will, 2 died at the end of 2 weeks, 2 at the end of 8 weeks, and the other 

 5 lived 3, 5^, 6, 6^2, and 7 weeks, respectively. With no opportunity 

 to oviposit, 85 females, together with 43 males, were confined in a glass 

 tube and kept in partial darkness, with daily feedings of a mixture of 

 one-fourth honey and three-fourths water. Three of these females 

 lived to be 16 weeks old, 33 of the males died between the ages of 6 and 8 

 weeks, while 1 male lived to be 11 weeks old. The majority of the 

 females died between the ages of 11 and 13 weeks, while 15 lived a little 

 beyond this period. 



OVIPOSITION 



Oviposition takes place in only the larva of the host and may occur 

 at any time after the larva is one-half grown; but it is most frequent 

 in well-developed larvae. Observations of the female, just prior to 

 oviposition, indicate that she locates the host larva beneath the skin 

 of the containing fruit by a sense of touch. She walks rapidly over the 

 surface of an infested fruit, stopping at frequent intervals, evidently 

 endeavoring to detect vibrations caused by a feeding host larva. While 

 searching for the host, and during the act of oviposition, the female 

 often vibrates her wings rapidly and spasmodically, although this does 

 not always happen. When a favorable spot is found, she elevates her 

 abdomen and pierces the skin and pulp of the fruit with her ovipositor, 

 raising and lowering it until the host is located. She then inserts the 

 ovipositor into the larva and deposits an egg just beneath the skin. 

 Then she withdraws the ovipositor from the fruit and usually begins to 

 search for another larva; but occasionally, after a short rest, she will 

 oviposit again in the same one. The female is unable to discern between 

 parasitized and unparasitized larvae. 



Although mating may occur immediately after emergence, oviposition 

 does not begin until 2 days later and, in the majority of cases, 3 to 5 

 days after emergence. Eight fertile females were given constantly 



