REVISION MALACOSOMA HTJBNER EST NORTH AMERICA 157 



on small twigs and not on main branches. Another unusual behaviorism 

 was that larvae were reported to have a tendency to spin cocoons 

 together, with anywhere from one to six pupae being found per com- 

 munal cocoon. 



In 1 960 a local outbreak of c. pluviale was studied along Weiparous 

 Creek, near Fallen Timber Creek Campground about 60 miles north- 

 west of Calgary, Alberta, in the foothills of the Canadian Rockies 

 (Coll. No. 180). This population was in a boggy area, on Betula gland- 

 ulosa and associated willows, had a predominantly black larval color 

 pattern (fig. 372), and spun many "communal" cocoons near the 

 ground (fig. 337). It is believed therefore, that this population was 

 the same form as that reported by Grant. 



A careful examination of the egg masses showed them to be laid as 

 a basically flat clasping mass, and not as a complete band around 

 the twigs as reported by Grant. Most egg masses were laid on small 

 twigs, and consequently many appeared to surround the twigs, but 

 several were found on larger twigs and branches and clearly did not 

 encircle them. Some even were laid relatively flat on large branches. 

 Structurally, all life stages are indistinguishable from "normal" 

 c. pluviale except for the minor color differences already described. 

 They differ in the behavioral characteristics mentioned by Grant. 



Populations were very heavy in the boggy areas, but less than 100 

 yards away on slightly higher ground where many larger and seem- 

 ingly better individuals of Betula glandulosa grew, there were no tents 

 and not a single egg mass could be found. The only differences noticed 

 between the scrub birch at these two sites was that the birch growing 

 in the boggy area appeared to have been very heavily browsed (by 

 big game?) so that there were many small basal shoots, while that on 

 higher ground had apparently been only lightly browsed. 



Tents were constructed close to the ground almost invariably, 

 and in many cases they were actually touching the grass. There ap- 

 peared to be three species of willows growing in the area. Two of these 

 were untouched, but the third one had egg masses on it and the larvae 

 had completely stripped it. Despite their rejection of these two species 

 of willows, larvae reared in the insectary readily accepted a plant as 

 different as rose, and did quite well on it. 



It is difficult to imagine any advantage that can be obtained by using 

 a bog habitat instead of one on higher ground. There does not appear 

 to be an oviposition preference for Betula glandulosa which could 

 account for the difference, since there was plenty of it available on 

 higher ground that eggs were not laid on, and eggs were also laid on 

 one species of willow in the bog. Maybe there is something about the 

 conditions in the bog when the adults are present that attracts the 



