DEVELOPMENT OF A HYMENOPTEROUS PARASITE 541 
That these larval tubercles are not ambulatory is evidenced 
by their dorso-lateral position. Neither is there anything in 
their structure to suggest a sensory function. They appear to 
be prepupal growth structures, corresponding in size with the 
extent of the evagination of the underlying histoblasts. 
Similar structures have been observed in the mature larval 
stages of Perilampus hyalinus and Orasema viridis which may 
possibly be explained in the same way. 
The imaginal oenocytes are polygonal or rounded in outline. 
The cytoplasm is of a homogeneous structure and the oval nu- 
cleus presents a granular appearance, but the granules are larger 
and less numerous than those in the larval oenocytes. In the 
tracheate larva, they lie closely packed together beneath the 
histoblast from which they arise and are of various sizes, those 
projecting farthest into the body cavity being the largest. Dur- 
ing the pupal stage they become much more scattered but still 
may be found most abundantly in the stigmatic regions of the 
abdomen. After proliferation from the histoblast, there is a 
steady increase in size, but no instances of subsequent divisions 
were observed. 
Nothing was discovered regarding the function of the oeno- 
cytes of Spalangia. Glaser (12) found that the oenocytes of 
the leopard moth, Zeuzera pyrina L. secrete oxidizing enzymes 
which may activate the oxygen of the body. The oenocytes 
which he studied are found only in the abdominal segments just 
behind the tracheae and are apparently homologous with the 
imaginal generation of the Spalangia oenocytes. Whether the 
larval and imaginal oenocytes lave a like function must remain 
an open question for the present. 
The adipocytes are large single cells, spherical in outline, which 
float freely in the blood. In preparations stained with iron 
hematoxylin, the nucleus of each cell appears as a stellate mass 
of darkened chromatin granules. Outlines of the fat vacuoles 
are distinguishable, the contents, of course, being extracted by 
the xylol. Darkly stained globular bodies are abundant in the 
cells and are probably albuminous. Comparison of the adipo- 
cytes of the atracheate and tracheate larvae shows a steady 
