262 C. T. BRUES, 
Large muscles now begin to develop in the thoracic portion ot 
the larva. These are asymmetrical and larger in the male than in the 
female. On each side of the alimentary tract there are two of these 
cigar-shaped muscles attached as shown in Fig. 22, the proximal ends 
of those on one side being attached below the gut, while those op- 
posite pass above the gut. The object of such a peculiar asymmetry 
is most probably connected with the way in which the larva later 
pushes its head between the sclerites of its host’s abdomen. Con- 
siderable muscular effort must be required for this purpose and more 
in the case of the male which has a very blunt anterior extremity. 
The relation which these muscles bear to the later wing and leg 
muscles of the male still remains to be elucidated. 
The testes are well developed in the smallest male larvae which 
we have obtained. Such larvae which are scarcely more than 2 mm 
in length have the testes large and extending throughout almost the 
entire abdominal region. In cross sections through this portion of 
the animal from two to six testicular follicles appear on each side of 
the alimentary tract. The tubules are separated and number four on 
each side. Each separate follicle is enclosed in a very delicate mem- 
brane, but no common scrotal membrane is present. The follicles 
extend over the eight anterior abdominal segments, being more or 
less folded back and forth on themselves to conform with the meta- 
meric constrictions of the alimentary tract. The vasa deferentia meet 
in the median line near the base of the ninth abdominal segment and 
the ejaculatory duct seems to have a distinct opening at the apex of 
the tenth segment. 
After another moult it is easy to distinguish the sexes by the 
external form, the female being considerably more attenuate than the 
male. After another period of growth the male changes in form and 
goes into the pupa stage, which lasts just about a week in this species. 
The female assumes the form shown in Fig. 24 and 25. Whether a moult 
occurs after this stage in the case of the female is doubtful, although 
considerable change takes place in the head segment before it as- 
sumes completely the adult form, due in great part to a flattening 
and greater chitinization of the head. 
As some misunderstanding still exists (see SHARP, 1899) con- 
cerning the orientation of the mature female in the body of the wasp, 
it may not be amiss to consider this point here. Von SIEBOLD (1842) 
rightly believed the protruded portion of the female to be morpho- 
logically the head. Mrrert (1896) suggested that the posterior ex- 
