MEMOIRS 





OF THE 



BOSTON SOCIETY OF NATURAL HISTORY; 



YOLUME IV, mJMBER III. 



THE INTRODUCTION AND SPREAD OE PIERIS RAPAE 

 IN NORTH AMERICA, 18G0-1885. 



By SAMUEL H. SCUDDER. 



BOSTON : 



PUBLISHED BY THE SOCtETY. 



September, 1887. 



