Nov. 25, 1918 



Biology of Fruit-Fly Parasites in Hawaii 



427 



short, sharp, cur\-ed spines with broad bases (fig. 12, 13). These 

 spines are absent along the line of articulation between each segment. 

 The body averages 3.1 mm. in 

 length and about i mm. in width. 

 The characters of the head are 

 strongly developed (fig. 14). A 

 well-defined labrum, heavily pointed 

 mandibles about 0.12 mm. long, with 

 broad rounded bases and brownish 

 chitinization at the tips and bases 

 (fig. 15), distinct maxillae with short 

 major and minor palpi, and a chiti- 

 nized labium with palpi, can be dis- 

 tinguished readily. The palpi are 

 only short tubercles. Well-devel- 

 oped, yellowish, tentorial ridges in 

 the head support the mouth parts. 

 The mandibles and tentorial struc- 

 tures of the head are colorless at 

 first. Some hours after the molt 

 they assume the yellowish-brown 

 color that so readily distinguishes 

 this instar from the preceding. The 

 head is about 0.5 mm. in width. 

 As the remaining food consumed b>- 

 this instar is liquid, the purpose of 

 the well-developed mandibles, which 

 may be vigorously moved, has not 

 as yet been established. No change 

 takes place in the alimentary canal 

 upon the molt to this instar. The 

 larva is very sluggish, though it may 

 bend its body slowly from side to 

 side. It usually Hes with its head in 

 the head end of the puparium. Of 

 76 parasitized fruit-fly puparia 

 opened to determine this point, 64 

 contained mature Diachasma tryoni 

 larvae in this position. In the 

 remaining 12 the position was 

 reversed. When in the first instar, 

 the larva moves about with its head 

 in no constant direction. 



The duration of the mature larval stage is of unusual interest. In 

 Hawaii it may extend fiom about 6 days to over a year. Larvae ordi- 



Fig. 11.— Diachasma tryoni: Larva of fourth in- 

 star, lateral aspect, showing complete right 

 tracheal trunk with tranches and stigmata. 

 Length 3.1 mm. 



