34 BULLETIN 427, U. S. DEPARTMENT OE AGRICULTURE. 
DIBRACHYS BOUCHEAXUS RATZ. J 
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 Habwbracon 
Fig. 17. — Dibrachys bouclieanus: a, Larva; &, pupa: c, adult female; d. head of larva; e, antenna of 
male, highly magnified. Greatly enlarged. (After Howard.) 
jolmnnseni and Ohdonus slwslioneanorum, the former seeming to be its 
favorite host. This species was reared from the egg in the laboratory, 
where it attacked the mature larvae 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 
the hyperp ar asites in- 
crease rapidly, but 
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 johannseni. With Ohelonus 
shoslioneanorum 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, Dibracliys boucheanus was noted on only a few 
occasions. 
Fig. 1; 
Zagrammosama fiavolineatum: Adult male, with lateral 
view of head. Much enlarged. (Original.) 
1 Chittenden No. 2230°o. 
