go PROCEEDINGS OF THE NATIONAL MUSEUM vol. 91 



Ihe predisposition to variation is greatest, more stability being apparent 

 to the east and west beyond the intermountain area. 



The larvae are probably rather general feeders, a character common 

 to many arctiids, but only a few have been reared. 



Dr. J. A. Comstock, director of science in the Los Angeles Museum, 

 kindly sent material for study, for which thanks are due. 



A diagnosis of this well-known genus is not included, but descrip- 

 tions of the genitalia follow. 



The drawings for this paper were made by Mrs. Eleanor A. Carlin, 

 of the Bureau of Entomology and Plant Quarantine. 



Genus ARACHNIS Geyer 



Arachnis Geyeb, in Hiibner, Zutrage exotischer Schmetterlinge, vol. 5, p. 28, 

 1837. 



Male genitalia. — ^Harpe broadly attached a', base, long, slender, al- 

 ways with inward lateral projection. Anellus semicylindrical, some- 

 times concave laterally. Aedeagus long, stout, dorsoventrally curved ; 

 vesica with numerous minute scobinations. Vinculum with well- 

 developed winglike lateral expansion. Tegumen with well-developed 

 dorsal flange. 



Female genitalia. — Ostium large, extending well beyond ventral 

 surface of genital plate. Ductus bursae strongly sclerotized, some- 

 what depressed, concave ventrally. Ductus seminalis greatly enlarged, 

 membranous or partly sclerotized, and entering at confluence of ductus 

 bursae and bursa copulatrix. Bursa copulatrix with two small, 

 round, scobinate signa. Occasionally a third signum is weakly 

 developed. Dorsal glands well developed, with several branches. 



Remarks. — The lateral projection of the harpe does not seem to 

 represent a clasper or an ampulla, but rather no more than an out- 

 growth of the ventral margin. 



KEYS TO THE SPECIES OF ARACHNIS 



Coloration 



1. Hind wing with yellowish ground color 2 



Hind wing with red or reddish ground color 3 



2. Thorax with conspicuous white posteromedian dorsal spot ; dark 



markings of fore wing slate zuni Neumoegen (p. 69) 



Thorax without white posteromedian dorsal spot; dark mark- 

 ings of fore wing gray midas Barnes and Lindsey (p. 69) 



3. Fore wing with white or whitish ground color 5 



Fore wing with ground color otherwise 4 



4. Fore wing with yellowish ground color. 



picta citra Neumoegen and Dyar (p. 67) 

 Fore wing with cerise ground color apachea, new species (p. 68) 



5. Abdomen with lateral row of orange spots 6 



Abdomen with lateral row of gray to blackish spots 7 



