62 ENTOMOLOGICAL SOCIETY OF 0^lTARIO. 



protodice. Not being informed about the advance of rapce, I did not suspect its presence 

 until the following winter, when upon a visit to Dundas I saw specimens of it in Mr. 

 Kyle's collection which he had captured in his own garden the previous summer without 

 suspecting that they were other than a variation of the native protodice. So that if I had 

 examined closely, I have not the slightest doubt but I would have found rapoi helping to 

 swell the numbers that so attracted my attention during the autumn collecting ; coahrm- 

 ingMr. Scudder's expectations. Moreover, I found rapa' in the spring of 1873, indicating 

 that it must have been present the previous fall. From that onward, I saw no more pro- 

 todice, their place being taken by rapce. And this I believe corresponds with the expe- 

 rience of Canadian collectors. 



I have never seen this sudden and total disappearance of Pieris protodice satisfactorily 

 accounted for. When I have seen the subject touched upon, it has usually been dis- 

 missed with a reference to " the straggle for existence and the survival of the fittest," 

 •which does not seem to me to apply in this case at all. The breeding habits of the two 

 differ considerably ; the native j^rotodice was quite content to make use of the natural 

 products of the soil for its purpose, whilst the imported rapce attacks first, and in pre- 

 ference to all others the cultivated ones. So there need have been no " struggle" betr^een 

 the two on that point, as there was plenty for both, and as the larv;v of rapce had an 

 abundance of vegetable food to its liking, it would not devour that of the other even if 

 it had met with it on the same plant. As that theory does not account for the disappear- 

 ance of protodice, I have to look for one that will meet the requirements of the case. 



It is a well-known principle in biology, that there are races of animals of the same 

 species, that are possessed of different constitutions and dispositions, and that there are in 

 nature, external influences at work which, acting upon the living organism will produce 

 such differences. That in some instances, such differences manifest themselves geographi- 

 cally, and are spoken of as geologic and climatic, or as pertaining to the soil and climate. 

 That races may differ in strength of constitution and character according to the part of 

 the globe to which they belong. And that a strong race commingling with a feeble one, 

 will impress its peculiarities upon the results of such a union and make its controlling 

 power manifest. 



Now it is generally admitted, that the life of Europe is of a more vigorous, tenacious 

 and aggressive character than that indigenous to this continent ; therefore I come to the 

 conclusion that protodice and ra^jce are but different races of the one species, and that 

 when they met and commingled, the stronger constitution and proclivities of rapce pre- 

 vailed, and the outcome of the union were all stamped unmistakably rapce, the characteris- 

 tics of protodice being completely absorbed and obliterated. This seems to me to be quite 

 sufficient to satisfactorily account for all that has occurred in connection with these two 

 butterflies, and u it is correct then the probabality amounts almost to a certainty, that, 

 sooner or later protodice will return. This is not a prophecy, but a simple deduction from 

 the well known laws of nature ; for the external influences that produced the typical pro- 

 todice and brought it into harmony with its environment at first are still at work, and 

 working in the same direction. Therefore, when these external influences have had suffi- 

 cient time to work their utmost upon rapce, and no fresh importations take place, a 

 reversion to the original type will be brought about as a matter of course. 



In seasons of its greatest abundance, protodice never caused any serious injury to 

 cabbage, in this northern portion of the continent at least. Its larva was quite content 

 to feed upon the loose outside leaves of the plants, and so did but little harm; but the 

 larviB of ra^JCB will eat their way into the solid heart of the largest heads, injuring them 

 greatly, if not ruining them utterly. If then protodice should return with its original dis- 

 position unimpaired and supplant rapce, it will be a welcome transformation to the culti- 

 vators of that useful vegetable. 



