OK NORTH AMERICA. 119 



subcostal veins have their origin 'inside the discal vein, which is much 

 stronger, while the 2d median nervule is as far from the ist as from 

 the 3d. Finally, the style of ornamentation is quite different, the 

 anterior wings being obscure, and the posteriors destitute of discal 

 spots. 



The present genus includes insects of most difficult specific deter- 

 mination. After an examination of over sixty specimens I have de- 

 cided to describe what appear to be three distinct forms, although I 

 am by no means certain that subsequent investigation will not prove 

 them all variations of the same insect. At present we merely know 

 that these insects are all found in the same localities, on both sides of 

 the Sierra Nevada Mountains, and very widely distributed over the 

 Pacific Coast from Northern Oregon to Central California, and perhaps 

 even further southward; the home of the genus, judging from the 

 size and color of the specimens, being Oregon. The three species into 

 which I have divided the specimens before me are clearly marked, 

 though differing considerably even among themselves; but the circum- 

 stances under which they are found, and their extreme variability, 

 strongly incline me to the belief that they are one and the same species, 

 .although the fact is not yet proved. Should they prove to be identical 

 Z. Lena must be retained as the specific name and the other forms 

 noted as varieties. 



Boisduval describes three varieties of this genus, two of them from 

 individual specimens, as belonging to Lithosia (!) and includes with 

 them in the same' genus two species of Cisthene, though he subse- 

 quently says the three former "should perhaps be placed in a new 

 genus near Nemeophila !" Such careless work is greatly to be regret- 

 ted from the pen of the great entomologist, for if they were near 

 Nemeophila, as they undoubtedly are, it would have been far better to 

 include them in that genus, than in one with which they have no rela- 

 tion whatever. And here it may not be out of place to say, that so 

 far as Boisduval's writings relate to Californian Bombycidaj, they are 

 totally unreliable and liable to produce confusion, rather than to re- 

 move it. Many insects are included the occurrence of which there is 

 much reason to doubt, and many species well known to American 

 entomologists are described under new names. 



The three species may be tabulated as follows : 



Lower wings red - - - Z. decia. 



Lower wings yellow - - - - Z. Una. 



Lower wings black - - - - Z. dimidiata. 



