78 
Psyche 
[Vol. 90 
Acknowledgements 
We thank E. W. Evans and M. K. Hausmann for technical 
assistance. N. F. Johnson and B. M. O’Connor identified the parasi- 
toids and mites respectively. The research was supported by NSF 
grant DEB77-25120. 
Summary 
Morphological and behavioral defenses of Exema canadensis are 
illustrated with scanning electron micrographs. In laboratory exper- 
iments, the fecal case was shown to protect larvae from three pre- 
daceous insects (a nabid, a pentatomid, and a coccinellid) that occur 
in the same microhabitats with E. canadensis. Exposed larvae were 
readily consumed by predators. The case did not deter parasitoids; 
larvae were heavily parasitized by a eulophid, Tetrastichus sp., and 
pupae were attacked by a chalcid, Spilochalcis albifrons. Other 
enemies include mermithid nematodes and erythraeid mites. The 
adaptive syndrome associated with the case-bearing habit and its 
possible evolution are discussed. 
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