1988] 
LaMunyon — Chrysopa comanche 
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two ways. Some were fixed in formalin, dehydrated in ethanol, 
embedded in paraffin, sectioned at 8 microns, then mounted and 
stained with hematoxylin and eosin. Others were fixed in 4% gluta- 
raldehyde in 0.01 M phosphate buffer (pH 7.2 at 5°C), post fixed in 
2% osmium tetroxide in 0.01 M phosphate buffer (pH 7.2 at room 
temperature), dehydrated in ethanol, embedded in Epon-Araldite 
502, sectioned at 1 micron, and mounted and stained with toluidine 
blue. In all, 12 larvae and 6 prepupae were sectioned and examined. 
Empty cocoons were also examined microscopically. Some were 
embedded in paraffin, sectioned at 40 microns, then mounted and 
stained with eosin. Others were fractured after submersion in liquid 
nitrogen, mounted on stubs, sputter-coated with gold, and viewed 
with a scanning electron microscope. 
Results 
In mature third-instar larvae, the defensive substance is stored in 
the hindgut, which has a very thin epithelium (Fig. 1 A). In prepupae 
spinning silk, the epithelium is greatly enlarged and villous, extend- 
ing into the lumen (Fig. IB). Two substances are visible in this 
section: an innermost eosin-staining material continuous with mal- 
pighian tubule-produced silk precursors, and an outer, non-staining 
substance associated with the villous epithelium. In prepupae fixed 
after spinning the outer layer of cocoon fibers, the epithelium is still 
unusually enlarged, and long, finger-like extensions into the lumen 
are visible (Fig. 1C & ID). At this stage, only the epithelium- 
associated substance remains. 
In the paraffin cocoon sections, there were two different materials 
present: the outermost silk which stained with eosin, and the non- 
staining substance making up the solid inner wall (micrographs not 
included). These two cocoon layers appear discrete in the electron 
micrographs. The inner wall is relatively thick, is surrounded by the 
fibrous silk, and is the major component of the cocoon (Fig. 2 A, B, 
C). Figure 2C also shows a pore through the inner wall; all pores 
observed were composed of two holes. The homogeneity of the 
inner wall is evident from Fig. 2D. 
The abdominal musculature changes during transition from 
mature, third instar larvae to prepupae. Large, intersegmental mus- 
cles can be seen traversing the section of a younger larva (Fig. 1 A). 
The defensive substance, being less viscous than cocoon precursors 
