DURATION OF LARVAL PERIOD in 



I feel sure that I need not apologize to the 

 reader for the length of the above extracts, in- 

 asmuch as the subject, especially as treated by its 

 author, is one of such great interest. 



In writing of the Ephemera, Mr. Wood states 

 that they remain in the larval state for at 

 least three years ; but on referring to his work 

 ' Insects at Home/ I find that he assigns a 

 period of two years. I conclude that, as the 

 latter work was written some time after the 

 former, the shorter period may be taken to be 

 the more correct. 



I have consulted all the leading works on ento- 

 mology, and have also, in the absence through 

 illness of Professor Westwood, made inquiries at 

 the Ashmolean Museum in Oxford indeed, done 

 my utmost to try and ascertain if the period is 

 definitely known but I can obtain no positive 

 information. Suffice it to say that two years may 

 be taken to be the average time. There was, some 

 few years ago, a considerable amount of discussion 

 on the subject. At that time attempts were being 

 made to transport the mayfly (of course in its 

 creeper stage) ^from rivers where it was plentiful 

 to those where it was unknown. Hence the 

 controversy. On reference to the Ashmolean 

 Museum, I was informed that the results of these 

 efforts proved successful, but that it was a matter 

 of some difficulty and trouble to acclimatize the 



