96 UNITED STATES NATIONAL MUSEUM BULLETIN 2 76 



(rarely a few of them may be pale); secondary dorsal setae orange 

 and conspicuously tufted anteriorly and posteriorly on each segment. 

 Lateral setae usually white, but occasionally yellowish; conspicuously 

 tufted around setal group L2. (A few larvae collected near Grants 

 Pass, Oregon, Coll. No. 12 IB, and near Bingen, Washington, Coll. 

 No. 127, had yellowish lateral secondary setae, but all other larvae 

 collected north of the Los Angeles area had white lateral setae.) 



LARVAL DIAGNOSIS. — No single character will identify constrictum 

 larvae as easily as some other species, but the combination of no 

 conspicuous middorsal markings, the hourglass-shaped, dorsal blotch 

 bordered by black spots, and the conspicuous tufting of both dorsal 

 and lateral secondary setae is sufficient to distinguish them from the 

 larvae of other species occurring within their range. 



EGG MASS. — The eggs are laid as a helical band which completely 

 encircles a small twig (fig. 107). They are covered with bright yellow 

 spumaline which contains large bubbles, approximately one per egg. 

 The spumaline is quite transparent, and the eggs are clearly visible. 

 Only M. disstria and M. tigris lay e^g masses which are similar in 

 being laid as a helical band which completely encircles a small twig. 

 Tigris egg masses, however, are not covered with spumaline (fig. 106), 

 and disstria &gg masses (fig. 1 13) are covered with dark brown spumaline 

 containing many different sizes of bubbles. 



TENTS. — M. constrictum and M. tigris are two species which do not 

 build large, conspicuous tents like those built by americanum, incurvum, 

 or californicum. Neither are they completely like disstria which builds 

 no tent at all. The term "tent" is used loosely in referring to tigris and 

 constrictum, since it usually consists of only a few thin layers of silk spun 

 between some twigs or a cluster of leaves, or of some silk spun on some 

 branches, twigs, or leaves similar to the way of disstria. The tents differ 

 from those oi americanum, incurvum, and californicum by being constructed 

 so that the outline of the tent closely follows the configuration of the 

 twigs or leaves it is built on, rather than being constructed with the 

 silk spun more or less straight across between twigs or branches. This 

 results in a tent with little or no space inside. Figure 334 shows an 

 unusually large tigris tent with attached exuviae left by caterpillars 

 after completing their last molt. The largest tents found (those used 

 for the last molt) were only about 3 to 4 inches wide at the widest 

 point. Such large tents are rare. Tents are generally much smaller and 

 tend to be more like the silken mats that disstria builds for molting. 



Both constrictum and tigris build their tents just prior to molting and 

 use them only as a base for attachment during molting. They never 

 rest inside the tent as do those species which build large tents. A new 



