456 



Journal of Agricultural Research 



Vol. XV, No. 8 



enough to ingest a visible quantity of food. As the Tetrastichus deposits 

 its eggs in clusters of 8 or lo, they become "encapsulated " in such groups 



(fig- 35)- 



The presence of the eggs of these parasites in this dead, inclosed state 

 offers no impediment to the normal development of the melon-fly larva 

 to the adult fly. The adult emerges and carries within its body, usually 

 in the fat masses, these eggs singly or in groups, until death. Death does 

 not seem to be hastened by the presence of the foreign bodies within the 

 body. On May 24 and 25, 191 7, 25 melon-fly larvae were stung by ie- 

 males of Diachasma fryoni and eggs deposited in each. The larvae were 

 then permitted to develop, pupate, and finally produce living adult flies. 



These flies were placed in 

 large jars and kept alive 

 for several months. On 

 June 4, 14, and 20, July 

 10, August 10, and Sep- 

 tember 27, a few of these 

 flies were killed and ex- 

 amined internally for evi- 

 dences of the parasite eggs 

 originally deposited in the 

 larvae. From i to 9 dis- 

 tinct, brownish, encysted 

 eggs of D. tryoni were lo- 

 cated in some portion of 

 the body of each of the 25 

 flies on the foregoing dates. 

 When, on September 4, 

 1917, as previously stated, 

 7 adults of Tetrastichus 

 gifjardianus were reared 

 from a melon-fly puparium 

 secured from the field, after such contradictory experiments had been care- 

 fully completed in March, renewed attempts were made to rear this species 

 in the laboratory from the melon fly. The possible significance of the 

 presence of the newly introduced melon-fly parasite, Opius fletcheri, 

 was immediately recognized. As the host larva was powerless to resist 

 the development of this parasite, it was assumed that a subsequent 

 oviposition by T. gifjardianus into larvae previously stung by O. fletcheri 

 might result in the rearing of adults of T. giffardianus. With this 

 object in view, melon-fly larvae were first subjected to attack by O. 

 fletcheri and then by T. giffardianus. As the rearings and examinations 

 from then on showed in every case where both species had parasitized 

 the larvae, the individuals of T. giffardianus developed and emerged as 

 perfect parasites, and in every case in which only the latter oviposited 



Fig. 35. — Tetrastichus giffardianus: Dead encysted cluster of eggs 

 removed {rem melon-fly pupa. Greatest width of capsule 0.36 

 mm. 



