24 THE BUTTERFLIES OF THE WEST COAST 



ally found, and not alone among the little ones, like the Lycwnas 

 mentioned, but also among the larger kinds, like Papilios, this 

 curious mix-up of the sexual ornamentation has been found. 



§ 17. Sex-Marks. 



About half of the species of butterflies are readily determined 

 as to sex, at a glance, by some obvious differences, such as the 

 anal claspers, or the different pattern of ornamentation of the 

 wings ; but there are others, especially among the Nymphalidce, 

 which are difficult to determine. In these cases the "lappets," or 

 the aborted fore legs which are folded over the prothorax, usually 

 afford a good point; the lappets of the males are fully clad with 

 plenty of long hairs, while the lappets of the females are less fully 

 clad in shorter and scanty hairs. 



The beginner is often puzzled to determine the sex of a speci- 

 men which later he would quickly know, as he became more 

 familiar with the complexion of butterflies in general. When 

 the butterflies are freshly emerged, and are unfed, and immature, 

 the sexes are more difficult of determination than later, when the 

 bodies of the females are developed and mature. 



§ 18. Gregarious Butterflies. 



One species of butterflies, Danais Plexippus, is at times gre- 

 garious ; they gather together in thousands, alighting thickly to- 

 gether in one tree, or at least as near together as possible. I have 

 noted these gatherings in spring and in the fall ; on the shore of 

 the Pacific, near Lx)s Angeles, and in Texas, and they have been 

 noted in other parts of the country, by other persons. These 

 gatherings are peculiar to this one species of butterfly; no other 

 species has any similar habit. When the conclave is disturbed in 

 any way they arise in multitudes, and fly about in a confused, un- 

 certain way, and at length settle down again as closely as before. 

 Many writers have noted these gatherings, but no one has offered 

 any plausible reason for the funny proceeding. They do not ap- 

 pear to have any leader, nor to have any especial business to trans- 

 act, or to be engaged in any social pleasures ; but just to get to- 

 gether, — only this, and nothing more. 



§ 19. Freezing. 



Butterflies can and do endure a freezing temperature without 

 suffering therefrom. In the high, alpine meadows of the Sierra 



