296 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 7 



They pupated June 9 to 14, and, again to the observer's surprise 

 adult Diplazon Icetatorius issued June 24 to July 1, requiring about 

 thirty-five days for development from egg to adult. 



On May 24, 1912, the writer reared several adult Diplazon Icetatorius 

 of both sexes from puparia of Syrphvs americanus. Two females 

 from this lot were confined in a cage with a Black locust twig on which 

 were ten Syrphid eggs among a lot of Aphis niedicaginis. They sought 

 out the Syrphid eggs at once and oviposited in each of them and in 

 some of them the second time. The Syrphid eggs- hatched May 26, 

 and larva) began feeding on aphids. They were nearly full grown on 

 June 12 when it became necessary for the writer to be absent front the 

 laboratory. On returning June 30, there were two Mesogramma 

 polita and six Diplazon latatorius in the cage. Mr. Irving Crawford, 

 while working under the direction of the writer at Wellington, Kan., 

 reared four Diplazon la'tatoriiis from puparia of Baccha clavata. The 

 Baccha clavata larvae, of unknown age, were collected on September 13, 

 1912; seven of them pupated on September 15; two adult Baccha 

 clavata issued on September 25 and four Diplazon Icptatorius issued on. 

 October 9. These data indicate that Diplazon Iwtatorius requires 

 about ten days longer to mature than its host. 



Messrs. W. D. Pierce and T. E. Holloway have described a similarly 

 complicated life-history of Chelonus texanus, Journal Economic 

 Entomology, Vol. 5, No. 6; stating in brief that Chelonus deposits 

 her egg in the egg of the host, but the parasite emerges not from the 

 egg but from the larva developed therefrom. 



Messrs. T. H. Parks, W. R. McConnell and R. A. Vickery of this 

 Bureau observed this peculiar habit of Chelonus texanus in the summer 

 and fall of 1912, the former rearing the species through two generations 

 in Laphygnia frugiperda, each of which required but twenty -one days, 

 the hosts in this case developing in twenty-four days. 



Mr. Parks and the writer reared great numbers of this same parasite, 

 from larvae of Loxostege similalis in the vicinity of Wellington, Kan., 

 in fall of 1909, during a severe outbreak of the latter species on alfalfa. 

 The Chelonus then so completely overcame the Loxostege that by winter 

 this pest was found only with great difficulty. In 1910, it was rarely 

 found and in 1911, '12 and '13, it had not yet become abundant, 

 which we have attributed to the effect of Chelonus. 



Messrs. H. M. Russell and F. A. Johnston (Journal Economic 

 Entomology, Vol. 5, No. 6) relate a parallel case in the life-history of 

 Tetrastichus asparagi. Given in brief, the adult Tetrastichus female 

 oviposits in the egg of its host, the adults issuing from the mature 

 larvai. Doctor Marchal observed this same phenomenon in Poly- 

 gnotus minutus in France with the added phenomenon of Polyembryony. 



