BITHYS QUERCUS. 



257 



minute portion, the dorsal head-piece, not easily distinguishable in 

 the living pupa (Chapman). 



Stridulation of pupa. — Constant writes {Cat. Lep. Saone-et- Loire, 

 p. 25) : The chrysalis can be heard, when it is taken between one's 

 fingers, to make very distinctly a sort of stridulation, analogous with 

 that made by certain longicorn beetles. He adds that he failed to discover 

 the means by which the sound was made. Parish observes (Ent., 

 xiii., p. 186) : Pupae were noticed in July, 1880, whilst being held in 

 the hand, to make a sound something like a squeak ; the sound pro- 

 duced being like that obtained when two stones, or marbles, are 

 knocked together in rapid succession, with an occasional louder sound. 

 As soon as the sound ceased a gentle shaking set them all squeaking 

 again. Fowler says (Ent., xxxiv., p. 17) : About forty pupae of this 

 species (obtained from larvae) were placed in a tin tobacco box, and the 

 latter by chance, was placed in a cardboard box. During the evening 

 I constantly heard a sound like the ticking of many watches, but with 

 a kind of slight rasping as well. Upon opening the tin all was quiet, 

 but, on gently tapping the tin, the sounds commenced again. I then 

 placed the tin upon the table and tapped, when the same ticking was 

 resumed, but it was not quite so audible. The position they first 

 occupied acted as a kind of sounding-board, and I could repeat the 

 experiment any number of times. All the pupae produced imagines, 

 so the sounds could not have been produced by parasites. Fowler also 

 refers (op. cit.) to the tapping made in a cardboard box by fallen pupae of 

 Eugonia polychloros, but this is a very different thing, for, in the pupa of 

 the latter species, the movable segments of the abdomen bring round the 

 anal end of the pupa with some force, but the pupa of Bithys quercus 

 is practically solid and incapable of any movement of this kind. [For 

 stridulation in the pupae of Callophrys rubi, see antea, p. 114.] 



Time of appearance. — The species appears to be absolutely single- 

 brooded, the greater number of specimens emerging between the first 

 week of July and the second week of August, but early examples 

 appear in some seasons by mid- June, and late examples in other 

 seasons in September, the period for almost any year extending over 

 some five weeks. There is little difference in the various localities in the 

 northern, southern, and southeastern parts of its range, e.g., July and 

 August are given for Scandinavia, June to August for Perthshire, July for 

 Tokat, and early August for Algeria, and the dates for central Europe 

 are practically identical with those of Britain, e.g., in Germany — June 

 and July in Pomerania (Paul and Plotz), in Hanover (Glitz) ; July in 

 Mecklenburg (Schmidt), at Wiesbaden (Rossler) ; from the middle of 

 June to the end of July in the lowlands of Baden, but lasting in the 

 mountains until August (Meess and Spuler), usually from the end of 

 June till early July (Schmid), and on into August at Munich (Kranz) ; 

 in July and beginning of August in Thuringia (Krieghofi), mid- July 

 and early August in East and West Prussia (Speiser), and at Elberfeld 

 (Weymer) ; in early seasons at the end of June in Hesse (Fuchs), but 

 generally from July until the end of August (Glaser) ; from June to 

 August at Eutin (Dahl) ; in July and August in Posen (Schultz) ; 

 from June till the beginning of August in Silesia (Doring) ; the end 

 of June and beginning of July at Obernigk (Nohr), as well as in 

 Upper Lusatia (Moschler), distributed throughout the Kingdom of 

 Saxony from June until August; in 1875, a specimen was taken at 



