60 THE REPORT OF THE No. 19 



has been on the Canadian liat, as having been known to be taken in Canada for fourteen years- 

 or more, but it has not yet been reported as having been seen in this city or vicinity, whilst 

 C. 12-pxmctatns will soon prove itself to be the more abundant and destructive species of the 

 two. 



Mr. E. M. Walker's observations on the spreading of Pieris protodice (Fig. 37) eastward , 

 given in the Thirty-second Annual Report of the Entomological Society of Ontario, page 87, 



aroused my interest in that butterfly, and I requested 

 the collectors in London to be on the look-out for it ; 

 but it was not observed here by any of them. The 

 season was unfavorable for rapae (Fig. 2.3), as it was 

 not nearly so plentiful as in ordinary years, and it 

 may well be regarded as yet more unfavorable for 

 protodice, which has been designated " The Southern 

 Cabbage Butterfly." In 1896 protodice was reported 



as plentiful at Windsor, Ont. It was also seen at 



Fig. 37. Pieris protodice ; colours, white and 



biacii. London where a few specimens of it had been taken 



the previous year. Since then it has not been observed in London. No further notice of its 

 movements has been taken, so far as I have observed, until Mr. Walker reported it as plenti- 

 ful at Leamington, Chatham and Sarnia. Which seems to indicate that it is recovering lost 

 ground eastward, but that its appearance at London in 1894 and 1895 should be regarded as a 

 sporadic outbreak, rather than as a permanent advance. The only fresh captured specimen of 

 protodice that I have seen this year came from Leamington. 



Desiring to locate its present boundary eastward, I made a trip to Glencoe. which is about 

 half way between Chatham and London im the Grand Trunk Railway, but found only rapae 

 there. So it has not yet got thirty miles east of Chatham ; and if it is gradually extending^ 

 eastward it will be several years yet before it reaches London along that line. But I am under 

 the impression that it will increase more rapidly along Lake Erie shore than it will inland, and 

 my intention was to visit Port Stanley in order to see if it had reached that locality, but a , 

 favorable opportunity did not present itself. 



If Pieries protodice is actually recovering lost ground, how slowly it is spreading eastward 

 as compared with the rapid advance of P. rapae westward upon its first introduction into the- 

 country. First taken at Quebec city in 1863, and considered likely to have been landed there 

 from Europe three years earlier, it reached Montreal in 1867. Belleville and Trenton in 

 1872. Port Hope, Toronto and Dundas in 1873. Paris and London in 1875, occuping western 

 Ontario and extending into Michigan in 1876. Thus in thirteen years time it spread from the 

 City of Quebec to the Detroit river. And the marvellous thing about it was that as rapae 

 advanced protodice disappeared, not leaving a trace of its previous existence in the locality. 

 New it has taken six years for protodice to get from Windsor to Chatham, and then it has not 

 got the whole ground to itself, but only getting to be in the majority. Clearly indicating that 

 protodice is meeting with a resistance of some kind to the reoccupying of its lost ground, which 

 rapae did not encounter in its progress westward. 



This is an occurrence of the most profound interest to every student of biology, and well 

 worthy of their closest attention and consideration. And in it may yet be found a key to the 

 solution of some of the most obscure and difficult problems of the day, in their relation to tha 

 science of life in natural history. 



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