176 UNITED STATES NATIONAL MUSEUM BULLETIN 2 76 



separated by the long, blackish primary dorsal setae which are always 

 present, and which i. incurvum never has (they are yellowish to white 

 on incurvum). Also, the dorsal orange markings of constrictum are hour- 

 glass-shaped and have a conspicuous black spot on either side of the 

 constriction of the hourglass. The dorsal markings of i. incurvum are 

 bordered laterally by black so that the black and orange together 

 form an oval mark on each segment. 



EGG MASSES. — Eggs are laid as a basically flat, clasping mass, 

 covered with relatively tough spumaline which contains many small, 

 fairly uniformly sized bubbles. It is nearly white or cream colored (fig. 

 117) in the populations north of Tucson, Arizona, but in the Tucson 

 area some t^g masses are covered with darker spumaline which may 

 even be very dark brown (similar to fig. 114). The spumaline never 

 has any specks in it as do many egg masses of M. calif ornicum (page 20) . 



TENTS AND COCOONS.— As described for M. incurvum (page 172). 



FOOD PLANTS. — Egg masses were collected on the following hosts: 

 Populus fremontii, Prunus virens, Salix sp., and peach. 



TYPE. — Lectotype, here designated, a male in the United States 

 National Museum. USNM Type No. 33658. Size: 26 mm. wing- 

 spread. Data: Arizona; Clisiocampa incurva Hy. Edw., Type, male; 

 Typicum specimen; Lectotype, Malacosoma incurvum (Hy. Edwards), 

 male, F. W. Stehr 1963. Genitalia in microvial labeled: Lectotype, 

 Malacosoma irwurvum (Hy. Edwards), male genitalia, F. W. Stehr 1963. 



PARALECTOTYPES.— One female, USNM. 



TYPE LOCALITY. — ^The original description gives only "Arizona 

 H. K. Morrison." H. K. Morrison collected in Arizona in 1881 and 

 in many other parts of the West (Mann, 1885). The lectotype falls 

 within the variation found in many populations of i. irwurvum collected 

 during this study along stream beds and in the irrigated lands from 

 Wickenburg southeastward to the Mexican border. It seems likely that 

 Morrison collected in the Phoenix area in 1881, and since the specimens 

 reared from the Phoenix area are very close to the type, the type locality 

 is restricted to the Salt River Valley at Phoenix. 



DISTRIBUTION (fig. 4).— As presendy known its distribution in 

 the United States seems to be limited primarily to areas in central and 

 southern Arizona along watercourses and irrigated lands where cotton- 

 woods and willows grow abundantly. Specimens were also collected at 

 higher elevations, however, especially in canyons (Coll. Nos. 211, 243, 

 244, 250). Its distribution in Mexico is completely unknown, but some 

 specimens from the vicinity of Mexico City and 6-10 miles W. of 

 El Salto, Durango, are identical in some respects with many specimens 

 collected from Tucson southward to the border. The Mexican specimens 

 are treated as the subspecies M. irwurvum aztecum because of the dif- 



