ENTOMOLOGICAL SOCIETY OF ONTARIO. 61 



As previously stated, I do not even pretend to have observed a one-thousandth 

 part of similar instances that have been goinj^ on in every locality each year. And I 

 repeat again, it is the cases where parasites fail to overcome a destructive insect, before it 

 occasions financial loss, that are the exceptional ones, and the nature of these failures is 

 such that we see and recoonize them lar more readily then where the reverse is the case. 

 It is the damage that we see, and this being the case, how can we see it before it exists? 

 Not only this, but I believe the great fundamental principle involved in the use of insec- 

 ticides is to assist parasites in doing their work ; and as we get to applying them more 

 and more intelligently, we shall watch for the exceptional cases where parasites are weak 

 in numbers, and by artihcial methods, seek to ofi'er a substitute for the lack of numerical 

 fitrength. 



A RE-APPEARANCE OF PIERIS PROTODICE BOISD. 



By J. Alston Moffat, Loxdox, Ont. 



On the 18th day of October, 1894, I received a P. protodice from Mr. C. Anderson, 

 a young collector of London, who has done some excellent work during the past summer, 

 by sugaring in his father's garden. A few days previously he had called on me to say 

 that he had seen on the street a white butterfly that was new to him. Failing to recog- 

 nize his description of it, I showed him the drawer containing the Pieris, when he at once 

 pointed to the female of protodice (see fig. 15) as like what he had seen. I gave him some 

 information about the peculiar history of that butterfly which excited his interest, and he 

 determined to make an effort to obtain some of them. With that end in view, he went 

 on the 17th to a locality which he thought was the one most likely for them to be found 

 in, with the result that he secured a pair of them, and when he showed them to me on 

 the 18th they were yefc alive. This is the first living pair of that butterfly that I have 

 seen since the autumn of 1872, when Pieris rapae, the imported cabbage butterfly appeared 

 on the stage to act its part, whilst the native one retired from view. 



In 1887, Mr. S. H. Scu'^der, of Boston, published a most interesting account of the 

 introduction and spread of Pieris rapa' from 1860, the year in which Mr. Couper captured 

 a few specimens at Quebec, where it is supposed to have been landed, and the first reported 

 to have been seen on this continent, to 1886, when it had reached the Rocky Mountains. 

 This history of the introduction and spread of P. rapce is full of interest and importance 

 to the cultivators of some of the most valuable products of the fleld and garden ; but the 

 fact, that as the imported rapae, advanced the native protodice disappeared, has ever seemed 

 to me to be one of the most singular and interesting events in natural history that has 

 come under my observation. 



I have seen the statement made by various writers, that Pieris oleracea, also native, 

 has disappeared from their locality on the advent of rapa\ This does not accord with 

 my experience. Oleracea I always found to be confined to certain locations, periodical 

 in its appearance and never very plentiful ; and so it has continued to be. But protodice 

 used to be more or less abundant every autumn until rapce came, when it totally disap- 

 peared from my field of observation. 



Mr. Scudder in tracing rapms gradual spread westward, siys : " In 1873, as before 

 stated, it reached Port Hope, and ' F. C. L.' reports taking his first specimen at Dunn in 

 Haldiraand county, Ontario, (Can. Ent. vi. 60), and some were taken at Hamilton (J. A. 

 Moffat), where one would have looked for it the preceding year from its presence then at 

 Toronto." 



I have always felt quite certain that rapiR was present at Hamilton during the fall 

 of 1872, although I did not notice it. My attention was arrested that season by the 

 unusual abundance of cabbage butterflies, which I set down without examination as 



