1988] 
LaMunyon — Chrysopa comanche 
207 
(personal observation), is probably expelled by compression of the 
entire abdomen. In prepupae, the circular and longitudinal hindgut 
muscles are enlarged and much more evident (Fig. IB, 1C), and 
probably expel the more viscous cocoon precursors by compressing 
only the hindgut. 
Discussion 
The hindgut epithelium changes quickly from a very thin layer 
to a villous tissue that is probably secretory. This inference is sup- 
ported by two facts. First, the malpighian tubules are the only 
organs opening proximally into the hindgut; these produce precur- 
sors of the fibrous silk, which stain differently than the epithelium- 
associated substance. Thus, the only tissue apparently responsible 
for the production of this latter substance would be the villous 
hindgut epithelium. Second, the appearance of this material coin- 
cides with the transformation of the epithelium (presumably to a 
secretory villous phase). The villous extensions are probably 
involved in secretion, and could be detaching from the cells and 
breaking open into the lumen. 
Insect hindgut epithelia normally secrete a thin layer of cuticle 
prior to molting, and the epithelium-associated material may be 
similar to some cuticle component. This finding supports the place- 
ment of chrysopid silk (pertaining to the epithelial substance) with 
the epithelial-produced cuticulin silks (Rudall and Kenchington 
1971). Other insect hindguts with a secretory function are known; in 
some tephritid flies a pheromone is secreted by a derived hindgut 
epithelium (Little and Cunningham 1987). 
It appears that the fibrous silk of the cocoon is produced by the 
malpighian tubules; the inner wall may be formed from the 
epithelium-associated substance. This hypothesis is supported by 
the temporal changes in the hindgut. The eosinophylic, malpighian 
tubule-produced silk precursors are found in the lumen during 
spinning of the fibrous silk. Once the silk layer appears complete, 
only the epithelium-associated material remains in the hindgut. This 
stage may coincide with the time when the inner wall is laid down. 
The gross physical nature of the cocoons also supports this hypothe- 
sis. After completion of the fibrous silk layer, the cocoons are very 
soft; ca. one day later, they become hard, probably as the inner wall 
is formed. 
