34 



BULLETIN 427, U. S. DEPAETMENT OF AGEICULTUEE. 



DIBRACHYS BOUCHEANUS KATZ. 



This well-known and cosmopolitan secondary parasite (fig. 17) 

 emerged from the tuber-moth material collected during 1912, 1913,, 

 and 1914, and, as shown by dissection, from both Hahrohracon 



a ' c * "" h 



Fig. 17. — Dibrachys boucheanus: a, Larva; 6, pupa; c, adult female; d, head of larva; e, antenna or 

 male, highly magnified. Greatly enlarged. (After Howard.) 



joTiannseni and CJielonus sJiosJioneanorum, the former seeming to be its 

 favorite host. This species was reared from the egg in the laboratory,, 

 where it attacked the mature larvse of its hosts after they had spun 

 their cocoons. Where the cocoons were not too thick to prevent it 

 from reaching its host 

 the parasite would 

 often feed at the 

 wounds caused by its 

 ovipositor. 



When reared under 

 laboratory conditions 

 thehyperparasites in- 

 crease rapidly, bub 

 under field conditions 

 their numbers are not 

 as large in proportion 

 to the host as might 

 be expected. During 

 1912 and 1913 the 

 percentage of para- 

 sitism ran as high as 

 50 per cent in the case of Habrobracon joTiannseni. With CJielonus 

 sJiosJioneanorum the average was much lower, the highest running 

 29 per cent. During 1914 the percentages in both cases were much 

 reduced, and while greater numbers of its two hosts were reared than 

 in the previous year, DihracJiys boucJieanus was noted on only a few 

 occasions. 



Fig. li.—Zagrammosoma flavolineatum: Adult male, widi lateral 

 view of head. Much enlarged. (Original.) 



1 Chittenden No. 2230'"'. 



