60 SMITHSONIAN INSTITUTION 



Just why the numbers of these two closely related butterflies should 

 vary reciprocally is not known. 



The disappearance of the yellow clover butterfly was only one of 

 the curious adjustments that took place as a result of the immigra- 

 tion of the orange form into this region. In the early years of its 

 occurrence in Virginia the intruder appeared first in the latter part 

 of April, and the earliest individuals were orange, like those seen in 

 summer but somewhat smaller. In 1931 it appeared earlier than 

 it had in previous years and in a different color. The early individuals 

 (fig. 61, a) were small and clear yellow with a slight flush of orange 

 on the inner and lower portion of the fore wings instead of orange. 

 Since then this small light form has appeared regularly in early 

 spring, usually early in April, in some years even in late March. 



In the West, spring individuals are small and yellow with a slight 

 flush of orange, the next brood is larger and wholly orange, and the 

 summer broods are still deeper orange (fig. 61, b). In Virginia 

 a few orange individuals fly in spring with the small yellow ones, and 

 in summer and autumn all three forms fly together. So if we regard 

 the conditions in the West as representing the standard pattern, 

 this butterfly has not as yet become fully adjusted to its surroundings 

 in Virginia. 



In 1937 bright clear yellow individuals of this butterfly some- 

 what suddenly increased in numbers, and they have been common 

 ever since. In that year also this insect first adopted the habit, so 

 characteristic of its eastern yellow representative, of sitting in sociable 

 companies on mud and sucking up the moisture. 



What further changes may take place in the habits or forms of this 

 interesting butterfly we cannot guess. But its curious history in 

 the past indicates that it will be worth watching in the future — 

 always with the hope that in Virginia it will not develop into the 

 destructive pest that it is in the irrigated lands of California and 

 Arizona. 



Of the disappearing butterflies the most conspicuous is the diana 

 fritillary (Argynnis diana), the range of which is becoming more and 

 more restricted. During the past season we obtained records of this 

 species from Buchanan. Tazewell, Wise, and Botetourt Counties, 

 from which it was previously unknown. 



Two new butterflies were added this year to the Virginia list. 

 Carroll E. Wood, Jr., and Lloyd G. Carr took Atrytone conspicua 

 (fig. 62, b, c) near Mountain Lake in Giles County, and Frank W. 

 Trainer captured Hesperia attains (fig. 62, a) at Farmville ; I caught 

 another of the latter species at Clarks Gap in Loudoun County. 



