DEFENSIVE ADAPTATIONS AND NATURAL ENEMIES 
OF A CASE-BEARING BEETLE, 
EXEMA C/lA/4D£A5^/N(COLEOPTERA: CHRYSOMELIDAE) 
By Richard B. Root and Frank J. Messina* 
Section of Ecology and Systematics, 
Corson Laboratory, Cornell University 
Ithaca, New York 14853, U.S.A. 
Introduction 
The larval habit of constructing and carrying a portable case has 
evolved many times in the Holometabola. It is a widespread trait 
of the Trichoptera and Lepidoptera (e.g. the Coleophoridae and 
Psychidae). Among the Coleoptera, casebearing is found in four 
related subfamilies of the Chrysomelidae, the so-called camptoso- 
mates: Clytrinae, Cryptocephalinae, Chlamisinae, and Lamproso- 
matinae (Boving and Craighead 1931). The larval case of many 
insects is thought to function primarily in defense by providing 
armor or camouflage (Otto and Svensson 1980). Here we describe 
the uses of the case and other defenses in a chlamisine beetle, Exema 
canadensis Pierce, and speculate briefly on the evolution and conse- 
quences of the case-bearing habit. 
The genus Exema Lacordaire contains nine species in North 
America (Karren 1966). All of the species appear to be univoltine 
and to feed on a fairly restricted range of herbaceous or shrubby 
genera in the Asteraceae (Jenks 1940; Karren 1966, 1972). In central 
New York E. canadensis is commonly found on goldenrods {Soli- 
dago spp.) and asters {Aster spp.). Its life cycle was summarized by 
Messina and Root (1980). Le Sage (1982) recently described the 
immature stages. 
Methods 
We observed the life history and natural enemies of E. canadensis 
during 1979 and 1980 at Whipple Farm, 8 km N.E. of Ithaca, New 
*Present address; Boyce Thompson Institute for Plant Research, Tower Road, 
Ithaca, New York 14853, U.S.A. 
Manuscript received by the editor January 24, 1983. 
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