272 THE ENTOMOLOGIST. 



be pulled across the back of a knife to remove the roughness of 

 the pin-holes. The object of using glass-headed steel pins is to 

 penetrate the wood, and the round glass head saves the soreness 

 to the finger caused by ordinary pins when much work has to be 

 done. The above described method can be equally appHed to 

 the English form of setting. I believe that tracing cloth and 

 glass-headed pins, as adjuncts in the setting of Lepidoptera, 

 were both introduced by that inimitable setter Mr. Arthur Cant, 

 who has probably operated on as many Lepidoptera as anyone 

 living. 



Iford Manor, Lewes. 



ON SEASONAL DIMOEPHISM IN BRITISH BUTTERFLIES. 

 By W. Haecourt-Bath. 



Fob some time past I have paid particular attention to the 

 seasonal dimorphism of our British Ehopalocera and the accom- 

 panying phenomena. I therefore perhaps may be excused in 

 ventilating my views respecting a certain point connected with 

 this subject which I wish to bring before the notice of the readers 

 of the 'Entomologist,' and that is the influence of the climatal 

 conditions in deciding the morphological characters. I will first 

 take the three common species of Pieris in order to illustrate 

 what I have to say. 



The seasonal characters of Pieris hrassiccs, P. rapes, and 

 P. napi are undoubtedly familiar to every entomologist. Those 

 of the first brood are so distinct from those of the second that 

 there could be no mistaking to which generation they belonged, 

 even by a tyro. These characters I have, however, observed are 

 subject to considerable modification or variation each season 

 according to the prevailing climatic conditions of the particular 

 year, namely the temperature and the amount of precipitation, 

 the two phenomena being generally intimately connected with 

 each other. 



As a general rule, I find that the earliest emergences of the 

 first generation in the spring partake of the distinctive or more 

 pronounced characters of the first brood to the greatest degree. 

 Those which emerge from the chrysalis state later assume more 

 of the characters of the second brood in accordance with the 

 increase of temperature ; which pertains a month or so more 

 advanced in the season. These earlier emergences are smaller 

 sized specimens than those which follow, and the black spots 

 and markings are in addition more obscure, — in the males, 

 indeed, being frequently almost entirely obliterated. When 

 reared through the winter indoors, where the temperature is 

 higher than that of the outside, the specimens of the spring 



