Dec. 15, 1920 Opius fletcheri, Parasite of the Melon Fly in Hawaii 429 



Fig. 10. — Opius fletcheri: Mandible of fourth- 

 instar larva. Length 0.075 mm. 



adults of Opius fletcheri emerged in the refrigerator, and each of 

 the remaining 432 unhatehed puparia contained a well-developed, 

 dead pupa of Opius fletcheri. A control lot of 500 parasitized 

 puparia that were held at the same time 

 at normal temperatures, 75 to 85 F., 

 produced 487 adult parasites and 13 

 dead pupae of Opius fletcheri. Seventy- 

 two and six-tenths per cent of the para- 

 sites developing in the refrigerator and 

 2.6 per cent of those developing at nor- 

 mal temperatures died while in the pupa 

 stage. These data seem to indicate that 

 it is difficult for Opius fletcheri to develop 

 through the pupal stage at a temperature 

 as low as 65 F. This mortality of pupae, 

 however, is not evident under field con- 

 ditions. While records of parasitism of the melon fly, which was devel- 

 oping in cucurbits collected in the field at all seasons of the year, were 

 being obtained, thousands of unhatehed melon-fly puparia were opened. 

 Although some of these records were secured when the temperature 

 ranged from 6o° to 70 F., less than 3 per cent mortality of Opius fletcheri 

 pupae was found. The cause of the high mortality of pupae in the refrig- 

 erator has not been determined. 



pupa ' 



In the process of transforming from the mature larva to the pupa 

 (fig. 12) this insect passes through a prepupal state of from one to two 



days. The larva be- 

 comes motionless. 

 The anterior portion 

 of the body, which is 

 to form the head and 

 thorax of the pupa, 

 becomes slightly con- 

 tracted, so that it 

 is somewhat smaller 

 than the remainder of 

 the body. The eyes 

 can be seen, forming 

 beneath the integu- 

 ment, as indistinct 

 reddish brown spots; 

 these become more 

 distinct and darker in 

 color until, just before the moltinto the pupal stage, they can beplainly seen. 

 In the last larval molt the skin is split from the head backward and, 

 by slight expansions and contractions of the body, it is pushed back over 



FlG. 11. — Opius fletcheri: Head of mature larva, dorso-cephalic aspect. 

 Width 0.63 mm. 



