On the Lengthened Period of the Pupal Stage in Sundry- 

 Species of Lepidoptera. 



By R. Adkin, F.E.S. Read April i$tk, 1905. 



On looking through the pages of the various entomological journals, 

 one frequently comes across records, under such headings as "Re- 

 tarded Emergence," " Abnormally Prolonged Pupal Stage," or such- 

 like, of moths that have been reared from the pupa? of some two or 

 more years before, and they are more often than not accompanied 

 by an expression of surprise that the moths should have come forth 

 after so long a period. I fear that I cannot myself disclaim the 

 authorship of some such a record ; but that was written in my younger 

 days, and the experience of many years has led me to believe that 

 such occurrences are the rule rather than the exception, at any rate 

 so far as concerns subterranean species and those that make substan- 

 tial cocoons. Indeed, even species having exposed chrysalids, such 

 as butterflies, can hardly be excepted, for it is a well-established fact 

 that a portion of a brood of Pieris napi will come forth in the autumn 

 and the remainder of it remain in pupa? through the winter, but as to 

 whether the two sets of circumstances are quite on all fours with 

 each other I am hardly prepared to say, although, on the face of it, 

 I see no reason for doubting that the same influences, whatever they 

 may be, are responsible for the result in either case. 



The following instances of prolonged pupal stages that I have 

 taken from my note-books will serve as illustrations, and it will be 

 noted that a considerable number of families are included. 



Perhaps one of the most striking cases is that of Asteroscopus 

 nubecitlosa. In the spring of 1884 the only five moths that were 

 reared of the brood emerged from pupa? that had lain over from the 

 summer of 1881, nearly three years having thus been passed in the 

 pupal stage. The circumstance at that time appeared to me to be 

 so remarkable that I was constrained to put it into print ("Entom.," 

 xvii, p. 142), and as, on looking up the note, I find there are at the 

 same opening of the volume similar notes with regard to other species 

 from the pens of such authorities as T- W. Tutt and O. P. Cambridge, 

 it is hardly to be wondered at that I at that time thought the occur- 

 rence unusual ; but on feeding up another brood of the same species 

 in 1890 I had to wait until 1892 for the moths to come out, and 

 from such information as I have been able to obtain I gather that 

 similar prolongations of the pupal stage are the rule rather than the 

 exception in this species. 



Notodonta chaonia is another species that appears to be very prone 

 to lying over. From twelve pupa? that I had in the autumn of 1902 



