THE BUTTERFLY'S NIGHTDRESS 



that at night he clings chiefly head upward to the 

 leaves and small stems of the underwood, the hazel, 

 for instance ; for late in the day, when the dusk is 

 near, I have not been able to find a single heath on 

 the bracken fronds. Now and then one may beat 

 him out of his night perch in the hazels, but it is 

 strange how rare this is in the wood. 



One word more on the common blue butterflies 

 at night. In not a good light one evening, I found 

 a large number sleeping on the brown heads of 

 plantains in a field of rough pasture. They did not 

 resemble their environment ; indeed, in a puny way, 

 they were in marked contrast with it. I saw some 

 on plantain heads six, eight yards away. As a rule, 

 one blue only occupied a plantain head, but in a few 

 cases a plantain was double-bedded. The nightdress 

 of the blue on its plantain is quite remarkable ; 

 sometimes it is more blue than grey. I have seen 

 scores of blues at rest this summer, but not one 

 which, by the colour or pattern of its nightdress, 

 matched, much less mimicked, its surroundings. I 

 should describe the purple hairstreak in its evening 

 or cold day grey, asleep on the green hazel leaf, as 

 on the whole less noticeable than the common blue 

 at rest ; but I cannot perceive the least mimicry of 

 environment about the purple hairstreak either. 

 The purple hairstreak which I have seen at rest a 

 few hours before writing this lays back its upper 

 wings in the same way as the other butterflies 

 mentioned. It appears in July, and may linger till 

 the end of August. 



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