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Psyche 
[Vol. 90 
the stalk and periodically twists the egg with her hind legs as she 
builds up the sides until the egg is enclosed in a cuplike case with a 
flared ridge (Figs. 1-2). A flat top is then added to seal the egg in the 
case. The flexible egg stalk often remains twisted beneath the case 
(Fig. 3). The entire deposition process takes 20-30 min in the labor- 
atory. The egg case turns a drab brown color as it dries. 
The larva emerges by chewing through the flat top of the case. It 
then flips the case over, presumably after severing the connection 
with the egg stalk (Karren 1972). Inside the inverted egg case, the 
larva assumes the characteristic folded posture of the camptoso- 
mates with the mouth and anus both adjacent to the single case 
opening. 
The larva begins to feed and gradually enlarges the case by adding 
its own fecal material to the rim around the opening. The juncture 
between the contributions of the mother and the larva remains dis- 
tinct (Figs. 4-5), and the original egg case eventually appears as a 
small nipple projecting from the tail of the larval case. A larva 
passes through four stadia, always molting within the enlarging case 
(Le Sage 1982). Case length is a moderately good predictor of larval 
instar, as determined by the width of the head-capsule (Table 1). 
Larvae of E. canadensis possess several morphological features 
that are probably related to the case-bearing habit. The legs are 
unusually long; each coxa is movable and so elongated that it 
exceeds the length of the femur (Fig. 6). The legs can extend later- 
ally beyond the rim of the case when the larva is walking. If dis- 
turbed, the larva retracts its legs and pulls the case down so that the 
rim is appressed to the foliage (Wallace 1970). The strongly recurved 
tarsal claws (Fig. 7) may facilitate this maneuver by providing a 
firmer grip on the substrate. The larval cuticle, which is normally 
covered, is sclerotized in only a few areas (Le Sage 1982). Setae 
(usually tricoid sensillae) are sparse, but spiny or rounded protuber- 
ances are scattered over much of the surface. These protuberances 
serve may to increase traction between the larval cuticle and the 
case. The larval spiracles are uniforous and annular (Fig. 8). The 
requirements for spiracular closure and moisture retention may be 
reduced in a case-bearer; Karren (1964) reports that artificially 
exposed Exema larvae are highly vulnerable to desiccation. 
The prepupa seals the case rim to a leaf or stem with a layer of 
frass. It then reorients itself so that the posterior end is against the 
