J. H. COOK'S DISCOVERY AT ALBANY 211 



NOTE. The capture of males of L. arcliippus in tvhich the black 

 stripe teas wanting from tlie upper surface of the hind wing, and 

 of transitional forms of both sexes, at Albany, N.T., by 

 John H. Cook. 



Mr. Cook first met with the stripeless form in June, 1898, 

 near Hudson, N.Y. A second specimen was captured near 

 his home in Albany in 1901, and a third in the same field 

 in the following year. This latter was a beautiful specimen 

 apparently only just emerged from the pupa. Mr. Cook's 

 attention was now thoroughly aroused and he collected 

 assiduously at Albany during three seasons, always working 

 on the best ground to the west of the city, and taking over 

 90 specimens with the stripe wholly or nearly suppressed. 

 The following conclusions were reached : (1) All the stripe- 

 less arcliippus captured were males ; (2) The females shared 

 the tendency but never reached the extreme found in the 

 other sex ; (3) Most of the individuals taken showed some 

 weakening of the stripe, varying from a slight break (most 

 commonly between veins III and V 2 and between V 3 and 

 VII 2 , of the system of Comstock and Needham) to complete 

 suppression on the upper surface. (4) At Albany individuals 

 with a broken stripe outnumbered those with an entire 

 stripe in the proportion of about 18 to 1, while stripeless 

 specimens were taken in the average proportion of 1 to 14. 

 Mr. Cook also collected data from other localities and 

 endeavoured to interest con-respondents in the problem. 

 Including the Albany material he secured records of about 

 1600 specimens and was able to reach the conclusion that 

 in New England and the Middle States broken-striped in- 

 dividuals are not uncommon though generally outnumbered 

 by those with a continuous stripe. He did not meet with 

 any record of a perfectly stripeless form except for his own 

 observations and the two specimens to which the name 

 pseudodorippus has been given. Strecker's type of this form 

 exists in Dr. W. J. Holland's collection (Butterfly Book, 

 New York (1899), 185). These two pseudodorippus were also 

 taken in the Eastern States (the Catskill Mountains, and in 

 Massachusetts), but Mr. Cook, who has seen one and received 



