460 



Journal of Agricultural Research 



Vol. XV, No. 8 



very little. It remains about the ground, entering crevices and crawling 

 under various objects, apparentl}' in search of fly puparia. In Hawaii 

 it has been reared from the puparia of several muscid species, but it has 

 never been reared from any material collected in the field. The female 

 may reproduce parthenogenetically, the resulting progeny being males. 



In the laboratory the female does not discriminate between parasitized 

 and unparasitized fly puparia. She will insert her ovipositor into any 

 puparium. If it contains only a developing fruit-fly pupa, the egg is 

 deposited into the pupa. If the puparium contains a parasitic larva, 

 which may be even one of the small Tetrastichus larvse, her ovipositor 

 will search out this larva and an egg will be deposited into it. A Galesus 

 adult ultimately may mature within this larva. It will, of course, be 

 dwarfed. These small adults are fertile. Such a habit indicates a 

 strong hyperparasitic inclination. 



During August, 191 7, a total of 195 fruit-fly larvae were parasitized 

 in the laboratory by Diachasma tryoni or Optus humilis. These larvae 



were then permitted to develop and to 

 form into perfect puparia. The puparia 

 were then immediately placed in cages 

 containing females of G. silvestrii and left 

 for 2 days. From 5 to 7 days later each 

 puparium was opened and the contents 

 examined. In every case the puparium 

 contained a dead opiine larva or occa- 

 sionally a pupa, in each of which was a 

 rapidly developing, strong larva of G. silves- 

 trii. This, then, was hyperparasitismpure and simple. To prove that these 

 larvae of G. silvestrii ultimately would develop to normal adults, a fresh lot 

 of heavily parasitized fruit-fly larv^ae was collected in the field. They were 

 variously parasitized by D. tryoni, D.fullawayi, O. htimilis, and Tetrastichus 

 giffardianus, and some were unparasitized*. The puparia thus formed 

 from the larvae were placed with 75 adults of G. silvestrii on September 26 

 and left for 24 hours. The puparia, 277 in number, were then removed 

 and each placed separately in a small vial to await emergence. From 

 this material 94 adults of G. silvestrii emerged, with both sexes well 

 represented. Each of the 94 puparia producing the adults of G. silves- 

 trii was then carefully dissected, opened, and examined. In 68 of the 

 puparia the empty shell of a mature D. tryoni larva was found, and in 

 each shell the cast mandibles of the larva of G. silvestrii as well as 

 the characteristic prepupal meconial discharge of G. silvestrii was dis- 

 closed. In 3 puparia a similar larval shell of O. humilis was found, each 

 with similar contents. In i puparium the shell remains of a mature 

 D. jullawayi larva was found, and in it also were the larval mandi- 

 bles and prepupal meconial discharge of G. silvestrii. In the remain- 

 ing 22 puparia which had produced adults of G. silvestrii remains of the 



Fig. 40. — Galesus silvestrii: Fruit-fly pupa- 

 rium showing characteristic emergence 

 hole made by adult parasite. Greatly 

 enlarged. 



