38 THE CANADIAN ENTOMOLOGIST. 



NOTES ON THE FORMS OF RUSTICUS ACMON (DB.-HEW). 



SCUDDER, OCCURRING IN THE VICINITY OF 



PASADENA, CALIF. 



BY VICTOR L. CLEMENCE, PASADENA, CALIF. 



For some time the writer has made a special study of the different 

 forms of Rusticus acmon. This special work has resulted in the possession 

 of large series of four distinct forms. 



From Boisduval's description of R. antcegon (which he admits is the 

 same as R. acmon), and by comparison with Doubl.-Hew., Plate 76, fig. 

 2, also with specimens from Boisduval's type locality, " les environs de 

 San Francisco," I have decided which of these forms is typical. I may 

 also add that Strecker's description in " Lepidoptera : Rhopaloceres and 

 Heteroceres, indigenous and exotic," also describes this form. 



Careful observations made during the last two seasons show that of 

 the other three forms two are seasonal, while the other is a new subspecies 

 occurring only in the mountains at an altitude of not less than 3,000 feet, 

 and frequenting only Eriogonum fasciculatum, which is probably its 

 food-plant, while that of the other forms is Hosackia glabra, generally 

 admitted to be the food-plant of true acmon or antcegon, 



The new subspecies, which 1 have named Rusticus montico/a, is a 

 much finer butterfly than acmon, being larger and more brilliantly coloured. 

 Of the remaining two forms, one occurs from February to April, is small 

 in size, of a darker blue than the type form, and heavily margined in 

 black, which leads me to think that the imagoes are produced from pupae 

 which have hibernated. The remaining form appears about May the 9th, 

 is larger than the preceding, resembling the type form, only is larger, and 

 has not such a pronounced violet tinge. 



The writer realizes the value and necessity of applying the test of 

 breeding in order to correctly classify these different forms, but owing to 

 daily observations and also the valuable help which he has received from 

 Mr. Fordyce Grinnell, Jr., feels assured that his deductions would be fully 

 justified by the above-mentioned test. From the length of time that acmon 

 is on the wing, from February till October, it may safely be assumed that 

 there are at least three broods; therefore, these different forms are probably 

 seasonal, as previously stated. 



Rusticus montico/a, n. subsp. — The type, 2 £ £ 's, 2 $ 9 's, are 

 taken from a series of 21 insects in the author's collection. 



January, 1909 



