432 Journal of Agricultural Research voi.xx.No. 6 



The adult (fig. 13) liberates itself from the host puparium by gnawing 

 a transverse slit near the end and by pushing with its head until the entire 

 end of the puparium breaks off, allowing it to emerge. Immediately 

 after emergence the meconium is discharged. This meconium is an 

 ovoid, hard pellet, consisting of all the waste material which has collected 

 in the digestive tract during the larval stage. No waste material is 

 voided before this time, although many braconids discharge it just prior 

 to pupation. 



Copulation may occur frequently, and at any time, from immediately 

 after emergence to the death of the adult. Two newly emerged females 

 were put into a glass tube with one male that had just emerged, and the 

 male successfully copulated with both females within 10 minutes. Nine 

 females that emerged May 18 to 20 were put into a tube with males, 

 where several instances of successful mating were observed. On July 1 , 

 when these females were 6 weeks old, they were put into a glass tube 

 with 30 newly emerged and vigorous males. Within 45 minutes 12 

 successful matings were observed, and one of the females mated four 

 times within 15 minutes. In all of these instances the females made no 

 great effort to escape from the males. The period of coitus lasts from 

 yi to 2 minutes, although in the majority of instances it is less than 1 

 minute. In six of eight cases under observation the duration was be- 

 tween 30 and 45 seconds, while in the other two cases it was extended to 

 \]/ 2 and 2 minutes, respectively. As far as it has been possible to ob- 

 serve, all of the sex attraction is produced by the male. When within 

 about 2 inches of the female, the male becomes greatly excited and 

 while slowly approaching her, and during coitus, vibrates the wings 

 vigorously and spasmodically. No strong, sweet odor, such as is emitted 

 by the males of the fruit-fly parasites Opius humilis Silvestri and Dia- 

 chasma tryoni Cameron, 1 has been detected during work with this species. 



Opius fletcheri is capable of parthenogenetic reproduction, and the ab- 

 sence of mating does not influence oviposition. Large numbers of adults, 

 all of which were males, have been reared from unmated females. The 

 fact that mated females will produce a considerably larger percentage 

 of females than males is of much interest. Eight females that were 

 observed mating within two hours after emergence were put into individual 

 glass tubes, where host larvae were available at all times. From these 

 females 39 males and 72 females were reared, giving 35.1 per cent males 

 and 64.9 per cent females. Under field conditions about 10 per cent 

 more females than males are produced. While records of parasitism of 

 the melon fly developing in cucumbers collected in the field during 191 8 

 and 1919 were being secured, 7,746 adult 0. fletcheri were reared. Of 

 this number 4,273, or 55.2 per cent, were females, and 3,473, or 44.8 per 

 cent, were males. Many species of opiine parasites consistently produce 

 more males than females. For example, the parasites of the Mediterra- 



1 Pembbrton, C E., and Willard, H. F. op. cit. 



