THE FIRST FOSSir, MYDAID FLY. 207 



separating Catoiisilia iiomona from C. crocale that ia adduced is 

 that C. jmiiona has red antenna3 and C. crocale black ones. 

 Judging from the behaviour of C. pyranthe in Hong Kong, 

 however, this is no distinguishing mark. Looking at a series of 

 twelve I bred here in June, 1912, I find that six are wet season 

 (form chryseis) with grey antennte, five are dry season with pink 

 antennae, and the twelfth, a sporting individual determined to 

 take no chances, has one grey antenna and one pink one ; other- 

 wise being of the dry form ! 



There are one or two points in connection with the mimicry 

 theory which puzzle me in Hong Kong. 



P. polytes has two forms of the female here, one of which is 

 like the male and the other is a " mimic " of P. aristolochice. 

 The mimicking form is almost as common as the ordinary form 

 of the female (polytes), yet I have never seen a specimen of 

 P. aristolochice, either on Hong Kong island itself or in the New 

 Territory, though it has been known to occur in Hong Kong. 



Again, Argynnis niphe, which is very common in Hong Kong 

 and on the mainland, has a female which might be said to 

 " mimic " D. chrysippus or D. genutia, both of which are also 

 common, especially the latter, which the female niphe most 

 resembles. But A. niphe does not, as a rule, occur at either the 

 same place or time as chrysippus or genutia. 



Niphe loves the open grassy hilltops, and genutia the woods 

 and edges of woods, keeping off hilltops altogether ; and chry- 

 sippus, although not likmg such woody spots as genutia, does 

 not occur on the breezy uplands with niphe. Moreover, niphe 

 occurs chiefly during the wet season, i. e., spring and summer, 

 and is hardly ever seen in the autumn here. Genutia, on the 

 other hand, is most plentiful in the late autumn, and Chrysippus, 

 when it occurs in the summer, does so in places where niphe is 

 practically never seen. Chrysippus also occurs in the autumn, 

 but is not so common as genutia. It seems, therefore, to be 

 waste of energy on the part of the female nijyhe in Hong Kong 

 to copy the colour- scheme of insects which she very rarely 

 comes across. Why is it done at all? She ought to have 

 reverted locally to the colour-scheme of the male. 



Hong Kong, 1913. 



THE FIRST FOSSIL MYDAID FLY. 



By T. D. a. Cockerbll. 



Handlirsch, in his great work 'Die Fossilen Insekten,' quotes 

 Scudder as reporting " several " Mydaidse (Midasidte) from the 

 Florissant shales. On looking up Scudder's exact words, we 

 find that he merely said he had " several species of Midasidae or 

 Hermoneuridfe." Since the latter family is represented by 



