184 UNITED STATES NATIONAL MUSEUM BULLETIN 276 



ADULT DIAGNOSIS.— At the present time this is the only large 

 tentbuilder recorded from Mexico, but M. calif ornicum most certainly 

 occurs in parts of Mexico. There are no known structural characters 

 which will separate M. incurvum aztecum from M. californicum, and any 

 differences in color patterns are as yet unknown since no specimens of 

 calijornicum have been collected in Mexico. The only other species of 

 Malacosoma known to occur in Mexico (outside of Baja California 

 where M. constrictum austrinum must occur) is M. tigris which is easily 

 identified in all life stages by the characters given for it (page 102). 



MATURE LARVAE. — Only a few preserved larvae have been avail- 

 able, so the following description cannot include all the variation that 

 undoubtedly exists. The specimens available are most similar to fig- 

 ures 391 and 394. Head blue, mottled with black, sparsely covered with 

 fine whitish to blackish setae. Middorsal area black, with only a few 

 faint orange markings. A very faint, narrow, broken, bluish-white 

 middorsal stripe may be present on some specimens. Addorsal area 

 black on all specimens examined. Subdorsal area black. Posterior sub- 

 dorsal spot sometimes present as a small blue-white mark. Subdorsal 

 line absent, or present as a yellowish mark on each segment. Supra- 

 spiracular area black with a few faint, irregular, bluish-gray markings 

 and some whitish-gray areas around the SV setal groups. Ventral area 

 entirely black, but some specimens will no doubt be found with gray- 

 white ventral areas and dark median spots. Both primary and secondary 

 dorsal setae pale golden orange. Primary and secondary lateral setae 

 white, or yellowish in some specimens, and tufted around setal group L2. 



LARVAL DIAGNOSIS. — ^To date, the only species known to occur 

 in the same area is M. tigris (page 105), which is identified by the charac- 

 ters given for it. (Larvae of tigris from Mexico have not been examined, 

 but they should not be greatly different from those found in the United 

 States.) All larvae of i. aztecum which have been examined to date are 

 similar to the dark phase of i. incurvum (figs. 391 and 394) which is 

 present to a certain extent in populations of i. incurvum found in south- 

 ern Arizona. Ancona (1930) discusses some light-colored larvae which 

 he observed with darker larvae, but neither his descriptions nor his 

 illustrations are good enough to determine if they are similar to larvae 

 found in southern Arizona. 



EGG MASSES (fig. 1 14). — Only five egg masses have been examined, 

 but all were laid as a basically flat, clasping mass, and all were covered 

 with dark brown spumaline which contained no specks. They are 

 virtually identical in color and other respects to a few egg masses with 

 dark spumaline obtained from reared specimens of i. incurvum collected 

 at Tucson, Arizona (Coll. No. 202). However, it would not be surprising 

 to find egg masses covered with lighter colored spumaline in populations 



