Hagen.] 138 [November 22, 



abundance was wonderful and indeed only to be compared with 

 an irruption. Every female before flying off was directly found 

 out by the myriads of males and impregnated. I only once remem- 

 ber to have seen a similar but still larger sudden irruption during 

 the destructive appearance of Bombyx monacha in Prussia. We 

 saw also Aug. 1, the species in West Montana. Other localities 

 recorded from which I have not seen specimens are Salt Lake, 

 Utah, by Lorquin ; Sierra Nevada, Lorquin, Dr. Behr ; Vancou- 

 ver's Island, H. Edwards ; San Juan Island, Bremner ; Mendocino 

 Co., and Mt. Shasta, Cala., Mr. A. Butler. 



The fact that Mr. A. Agassiz has found the species in large 

 numbers in the middle of May proves without doubt the exis- 

 tence of a spring brood ; as the other ascertained data Colville, 

 W. T., and Colorado show a summer brood at the end of July 

 and beginning of August, I am of the opinion that the exagger- 

 ated yellow females are probably the consequence of the immense 

 multiplication of the species, as similar facts have been observed, 

 if my memory is not wrong, in B. monacha. The whole brood 

 of P. menapia was overcrowded. The chrysalids were in the 

 furrows of the bark hanging down always half a dozen together, 

 and perhaps not well developed. Everybody knows that in the 

 artificially crowded broods of the common silkworm it is very 

 rarely, if at all, possible to find females with well developed wings. 

 Therefore I believe I am justified in concluding as follows : 



1. K. menapia has in Washington Terr, a spring brood; female 

 not yet known. Middle of May. 



2. 1ST. menapia has in Br. Columbia, Washington Terr., Colorado, 

 a summer brood. End of July. 



3. Females similar to the male when the brood is not crowded ; 

 Washington Terr., July 23, on a place not crowded, and Colorado. 



4. Females var. suffusa where the brood is crowded. 

 Concerning the caterpillar and chrysalis I gave up the attempt 



to point out the differences from other Pierids and principally 

 from L. sinapis because the statements in print are not suf- 

 ficient. The chrysalis in places not overcrowded is exactly as 

 described by Mr. H. Edwards ; in crowded places very different 

 in color, dark, nearly black. 



Mr. H. Edwards states that the chrysalis becomes black shortly 

 before transformation, and this seems very possible. The black 



