REVISION MALACOSOMA HUBNER IN NORTH AMERICA 141 



with larvae of M. californicum ambisimile which possess white lateral 

 setae and bluish lateral areas (figs. 354 and 355). If it is eventually 

 shown that M. californicum phiviale extends southward along the Pacific 

 Coast to Sonoma or Marin counties, then M. californicum californicum 

 should be found to intergrade with it, too. 



EGG MASS. — Eggs are laid as a clasping mass on twigs or branches. 

 The spumaline is dark brown and along with the spumaline of other 

 Pacific Coast populations (especially in California) differs somewhat 

 from that of populations found in the Great Basin and eastward. 

 The bubbles often are collapsed to a certain extent, resulting in a more 

 compact covering for the eggs. This is most apparent in egg masses 

 which have hatched, since there is often a separate hole in the spuma- 

 line where each caterpillar has eaten its way through as in figure 1 1 5. 

 In more eastern populations of californicum bubbles in the spumaline 

 usually remain uncollapsed, and hatching larvae often follow the 

 routes used by other caterpillars in finding their way through the 

 less compact spumaline (fig. 116). 



TENTS. — They construct large tents similar to other populations 

 of californicum, americanum, and incur vum. 



COCOONS. — Cocoons are fairly tightly spun, with or without an 

 outer envelope of silk, and dusted with a yellowish powder. 



FOOD PLANTS. — Egg masses were found on the following trees 

 and shrubs: Quercus lobata, Quercus agrifolia, Quercus kelloggii, Salix sp., 

 Rosa sp., apricot, almond, peach, prune, plum, and apple. It was most 

 commonly found on fruit trees, but also was abundant on Quercus 

 agrifolia at many different locations around San Francisco Bay and on 

 willows at several locations. See Appendix I for more complete data. 

 The native hosts before the introduction of fruit trees were most likely 

 Quercus agrifolia and willows. 



Plum seems to be a relatively poor host, since larvae fed on plum 

 grew very slowly compared with larvae fed on other hosts. For example, 

 some first instar larvae from Collection No. 5 which had been col- 

 lected on almond were fed plum, and others were fed Q. agrifolia, a 

 preferred host. Both groups were treated essentially the same, but when 

 those on Q,. agrifolia were in the last instar, those on plum were only in 

 the late third instar. A similar difference was noted in the field for 

 Collection No. 18 where colonies on plum were at least one instar 

 behind those on apricot. In the insectary, whenever larvae were given 

 a choice of several difference hosts, plum was always one of the last 

 to be eaten. Apparendy plum is either less palatable or less nutritious, or 

 both. 



TYPE. — Neotype, here designated, a male in the American Museum 

 of Natural History. Size: 27 mm. wingspread. This specimen is in 



