DEVELOPMENT OF A HYMENOPTEROUS PARASITE 5B YE 
chitinous ring still surrounds the mouth opening. The second 
segment bears a pair of -very small tubercles; segments 3 and 4 
are without tubercles, but a faint suggestion of them can be 
seen with high power binoculars; segments 5 to 12 each possess 
a pair, those on the posterior segments being noticeably smaller 
than those nearer the middle of the body. Of the imaginal 
structures which appear at this time, the most prominent are 
the thoracic legs and, in larvae destined to be females, a small 
group of appendages which will form the ovipositor of the adult. 
As in the atracheate larva, the digestive system (fig. 7) con- 
sists of a wide pharynx, a short, narrow oesophagus which is 
slightly enlarged just anterior -to its junction with the mesen- 
teron, a large mesenteron and a short proctenteron now differ- 
entiated as the ileum, colon and rectum, the first ending blindly. 
The salivary glands are greatly enlarged. 
The pharynx is an enlarged cavity separated by a slight con- 
striction from the mouth opening in front and by a larger con- 
striction from the oesophagus behind. A series of strong muscles 
radiate out from it to the integument. On the ventral surface 
of the mouth opening just in front of the pharynx is the small 
common opening of the salivary glands. Posterior to this open- 
ing, the salivary duct enlarges into a bulbous receptacle which 
receives the efferent duct of each gland at its posterior end. 
These ducts have a taenidial supporting structure resembling 
that found in the tracheae of the imago. 
The salivary glands are voluminous, filling a considerable part 
of the body cavity and extending well into the region of the 
proctenteron. Anteriorly, they are thin walled with a large 
lumen which is filled with secretion. They are obviously reser- 
voirs and not the active secretory parts of the organs. Poste- 
riorly, the lumen becomes smaller and the walls thicker until at 
a point just in front of the proctenteron region, the glands become 
multilobed and of greater thickness. 
The gland cells (fig. 8) are large, of an irregular shape with 
greatly ramified, granular nuclei, except in the thoracic region 
where they are narrow and elongate with elongate nuclei. The 
