462 



Journal of Agricultural Research 



Vol. XV, No. S 



been reared occasionally from fruit-fly puparia. It is not an important 

 fruit-fly parasite, but the interesting relations that may exist between 

 this and the other fruit-fly parasites has led to a laboratory study of this 

 species, with results worth recording. 



The female oviposits into the puparium, the &gg being placed on the 

 surface of the developing pupa within, and its larva develops on the 

 pupa as an external feeder. Thus from the first it bears a well-developed 

 tracheal system. The fly pupa is killed shortly after the parasitic larv^a 

 hatches and the lar\^a continues to feed upon the decomposing pupa. 

 It feeds much in the sense of a scavenger. It does not consume all of 

 the food in the puparium. The meconium is voided just before pupa- 

 tion and the pupa lies partly buried in the decayed remains of the fly 

 pupa and its own meconium. The adult parasite emerges 

 by cutting a small, circular hole in the puparium (fig. 

 41) and is immediately ready for mating and oviposition. 



«■ -l Another minute meconium is discharged immediately 

 I upon emergence. The female may reproduce partheno- 

 genetically with the resulting progeny all males. The 

 entire period from deposition of ^gg to emergence of adult 

 lasts onl}^ from 15 to 16 days. 



As the larva of this parasite is an external feeder within 



the puparium from the first, and the larvae of the other 



parasites are all internal feeders, the relationship between 



them is interesting. In a certain sense this parasite has 



■piG4i.—Pachycre- ^^^j^ provcd a primary, a secondary, or a tertiarv parasite. 



Fruit-fly pupari- As a primary it develops on the fruit-fly pupa, as a sec- 



um showing char- ^^^^^.y i|- dgvelops ou larvas or pupae of Tetrastichus 



actenstic emer- -' ^ '^ '■ 



gence hole made giffardiatius, Opius humiHs, Diachasma tryoni, D. fulla- 

 by adult parasite, ^^y.: qj. Qalcsus sUvestrii as they occur as parasites in 



Greatly enlarged. -^ ' j sr 



the fruit-fly puparium, and as a tertiary parasite it will of 

 course develop on a larv^a of G. sUvestrii, which in turn has been feeding in 

 the larvae of the above-mentioned opiines or T. gifjardianus. In the 

 laboratory,inlarge jars, this parasite indiscriminately oviposits intofruit-fly 

 puparia to bring about all of the above conditions of parasitism and may 

 be expected to act similarly in the field, when able to reach fruit-fly pu- 

 paria. Fortunately it does not show any decided capacity for penetrat- 

 ing soil in search of fly puparia and is probably more attracted to situations 

 harboring the dung-feeding species. The data demonstrating the various 

 capabilities of this species as a primary, secondary, or tertiary parasite 

 may be summarized as follows : 



During November 24 and 25, 1917, a total of 341 fruit-fly puparia 

 were secured from kamani fruits collected about Honolulu. These 

 puparia were variously parasitized by 0. humilis, D. tryoni, D. fullawayi, 

 and T. gifjardianus. On November 29 they were placed in a jar con- 



