REVISION MALACOSOMA HUBNER IN NORTH AMERICA 97 



tent is built before each molt, and after molting the tent is abandoned. 

 Between molts, the caterpillars cluster on branches (fig. 338) as does 

 disstria (fig. 332), or rarely on the outside of the old tent. 



In the field small tents are inconspicuous, and colonies of cater- 

 pillars are located more often by noticing a defoliated branch tip than 

 by spotting a tent. Even in times of high populations, defoliation is 

 much more noticeable than the tents. 



COCOONS. — Cocoons are fairly tightly constructed, have no outer 

 envelope of silk, and are dusted with a white powder. They are very 

 similar to those of tigris. 



FOOD PLANTS. — As far as is known, oviposition is restricted to vari- 

 ous species of oaks, but see the exception mentioned for M. constrictum 

 austrinum. Reports in the literature of constrictum occurring on hosts 

 other than oak are invariably larval feeding records, rather than egg 

 mass records. During the last instar, and especially during high popu- 

 lations, larvae may of necessity feed on other hosts, but these cannot 

 be regarded as their usual hosts since the eggs are normally laid on 

 oak. In the following host list, only those species are listed on which c^g 

 masses were found during this study, although it probably occurs on 

 all species of oaks which grow in the states bordering the Pacific Ocean, 

 Egg masses were found on the following hosts: Quercus agrifolia, Q,. 

 douglasii, Q^. garryana, Qj. wisHzenii, Q. durata, and Q^. kelloggii. 



TYPE. — None. See the discussion of types in Appendix II (page 283). 



DISTRIBUTION (fig. A).— M. constrictum constrictum inhabits the terri- 

 tory north of a line drawn from Indio, Riverside County, Calif., along 

 the southern base of the San Bernardino and San Gabriel Mountains as 

 far north as Washington. It is common on the west side of the Sierra 

 Nevada and will probably be found wherever oaks grow along the 

 Pacific Coast. Its eastward spread seems to be limited primarily by a 

 lack of oaks in the western part of the Great Basin and in the Mojave 

 Desert. 



ECONOMIC IMPORTANCE.— Af. constrictum (including the sub- 

 species austrinum) ranges from the relatively cool, moist areas of western 

 Oregon and Washington to the hotter and drier areas of southern Cali- 

 fornia and Baja California, so it is possible that it would do well in the 

 oak forests of the eastern United States if it should happen to be intro- 

 duced there. In the drier areas of the Coast Range at Pacheco Pass, 

 Santa Clara County (Coll. No. 42), and 4 miles east of Priest Valley, 

 Monterey County (Coll. No. 110), and in the foothills of the Sierra 

 Nevada, 18 miles north of Woodlake, Tulare County (Coll. No. 1 1 1) M. 

 constrictum constrictum was causing nearly complete defoliation of Q,. 

 douglasii. In the cooler, more humid areas along the northern Pacific 



