OF PIERIS RAPAE IN NORTH AMERICA. 59 



Ent. TI, 3-1:1). In further direction toward the northern l)and, Mr. Dimmock found '''a 

 few" at Bridgeport, Conn., in July, which may have belonged to the other group, but far 

 more proba]:)ly were the descendants of those that occupied West Farms the year before. 

 Dr. S. Lockwood tells me 'that it invaded Monmouth Co., !N^. Jersey, in 1870 and in Oc- 

 tober of this same year the editor of the American Entomologist saw it around fruit 

 stands in Philadelphia (Am. Ent. ii, 338) ; Mr. \V. D. Doan wi'ites me that it appeai-ed 

 in scanty numbers this year at Atglen, Chester Co., Penn., and Mr. Townend Grlover 

 in one of his Government Reports says that it appcai'ed even as far as Baltimore ^'an- 

 terior to 1870"; but this I think must be an error of memory. It ajipears then that the 

 southern horde did not this year quite reach the northern, but the two approached each 

 other so nearly as inevitably to mingle in 1871 ; that the northern had almost everywhere 

 reached the eastern seashore of ^cw England and the Canadian provinces, and on the 

 west had extended probably to Lake Ontario and nearly to central J^ew York. The 

 southern, on the other hand, had covered Long Island eastAvardly, and was pushing its 

 way also along the northern shore of the Sound, while its main army was directed south- 

 ward, had covered I^ew Jersey, and extended into eastern Pennsylvania. 



In the next year, 1871, these two armies, having devastated the country with independ- 

 ent forces for fully three years, met and mingled, and then swept westward and south- 

 ward with increasing rapidity. They covered all the gi'ound which lay between 

 the outposts of the previous year, this being the year in which it was first seen in 

 Rhode Island, at Providence (H. L. Clark), and at Hunter, IST. Y. (AV. II. Edwards). 

 It also extended to some of the higher regions pi"eviously untouched but swept past, 

 such as "Williamstown, Mass. ("in force" S. Tenney), and became as usual excessively 

 common where it had only appeared scantily the year ]:)efore. Thei-e were even some 

 spots not invaded until 1872, and it would appear that the advance guard, which sAvept 

 down the rivers flowing southerly and along the seacoast, left the inland districts long 

 untouched. Thus it is reported as not seen in Stowe, Mass., at the close of 1871 (C. A. 

 Emery). Mr. Dickinson showed to the Natural history association of Worcester in 1872 

 several specimens that had been' found in a garden there, as if they were of special in- 

 terest as new comers (so that the rumoi- that one was taken there in 1869, .'^upra, must 

 be an error), and it is thought not to have appeared in Sherborn until 1872 (A. L.Bab- 

 cock). By that time it had probaljly overrun every nook and corner of New England. 

 Similar irregularities appeal- in all its subsequent movements westward. 



Of its westward movement in 1871, we still have no information from northern New 

 York or noi-th of the boundaiy, and can only jiidge by subsequent notices that it must 

 have reached at least the extreme eastern end of Lake Ontai'io. It had certainly passed 

 the centre of New York, being found common at Ithaca this year (J. H. Comstock, L. 

 O. Howard), whei'e indeed it made its first appearance the preceding year according to 

 Mr. Howard, though Mr. A. C. Weeks thinks it did not occur in Tompkins Co. in 1870. 

 It was "troublesome" this j^ear or 1872 at Cazenovia (L. M. Underwood), while Mr. 

 Saunders states in his address to the Entomological society of Ontario (Rej). 1877, 5) 

 that "by 1871 it had travelled . . . west to the middle of the state of New York". In 

 Pennsylvania it is reported as harmful this year in Luzerne Co. (T. Glover), and as 

 present at Easton (Mrs. J. P. Ballard) and Lancaster (S. S. Rathvon) ; this does not 

 greatly increase its westward range. But it had pushed somewhat farther southwaixl, 



