68 
Psyche 
[Vol. 90 
York. Field-collected larvae and pupae were reared to measure the 
incidence of parasitoids. Voucher specimens of E. canadensis and its 
enemies were placed in the Cornell University Insect Collection (Lot 
no. 1068). 
The morphology of E. canadensis was examined with the scan- 
ning electron microscope. Larval cases and adults were air-dried 
and mounted on metal stubs with double-sided tape. Larvae and 
pupae were dehydrated in an ethanol series and critical-point dried 
with COt before mounting. All specimens were sputter-coated with 
gold-palladium (ca. 200A). Measurements of larvae and cases were 
made with an ocular micrometer. 
We did experiments on the protective functions of the case by 
exposing beetles to three predaceous insects: Podisus maculiventris 
(Say) (Pentatomidae), Nahicula suhcoleoptrata (Kirby) (Nabidae), 
and Hippodamia glacialis (F.) (Coccinellidae). For these experi- 
ments we carefully extracted 4th-instar larvae from their cases; this 
procedure did not appear to harm the larvae. “Exposed” and 
untreated (“encased”) larvae were placed in petri dishes containing 
moist filter paper and a few goldenrod leaves. In trials using P. 
maculiventris, two 5th-instar nymphs were taken from a vigorous 
lab culture and added to dishes containing three exposed and three 
encased E. canadensis larvae (a choice situation). We recorded the 
number of each prey type that were consumed by the stink bugs 
after 6 and 24 h. In trials using A. suhcoleoptrata and El. glacialis, 
field-collected adults were starved for 24, 48, or 72 h before being 
added to dishes containing either exposed or encased E. canadensis 
larvae (a no-choice situation). Each dish held three predators and 
five prey. We recorded prey consumption hourly for up to 5 h. 
Results 
The larval case and adaptations associated with its use 
In chlamisine beetles the female parent provides the initial larval 
case in the form of an egg case or “scatoshell” (Hinton 1981). The 
female deposits a single yellow egg that is attached to the plant on a 
smooth, yellowish stalk (Figs. 1-3) that appears to be continuous 
with the egg chorion. The attachment is shaped into the contours of 
the leaf or stem surface (Fig. 3), suggesting that the base of the stalk 
is extruded in a plastic state. The female then systematically sur- 
rounds the egg with strips of green fecal material. She starts around 
