1901 



ENTOMOLOGICAL SOCIETY. 



65 



Even the Horn Fly, Hceniatobia serrata, was first reported in the State at a point some 

 thirty miles east of Cleveland, though it appeared elsewhere soon after, and now we have 

 another illustration in the Willow and Poplar Curculio, Cryptorhynchus lapathi, found at 

 Ashtabula in the extreme northeastern county within a few weeks. This last appeared about 

 Buffalo, New York, in 1896. 



The foregoing illustrations will, I think, show clearly that there is a gateway opening into 

 Canada between the east end of Lake Erie and the western end of Lake Ontario as wide as the 

 Niagara River is long, through which insects introduced from Europe make their way, frequently 

 even when such have been firgj; introduced into Quebec, seemingly preferring to make their way 

 westward to the south of Lake Ontario instead of to the north of it. The gateway on the 

 United States side is along the south shore of Lake Erie, and between it and the northern 

 terminus of the Alleghany mountains. 



Map 2. — The dotted area shows territory over which Erynnis Manitoba, the Canadian Skipper 

 Butterfly, occurs and illustrates the southern trend of nordhern species. (Adapted 

 from Scudder.) 



The eastward trend of insect migration is followed, either by species whose native habitat 

 is along the foothills of the Rocky Mountains, or else by such as have come up from the far 

 south and swayed broadly to the eastward across northern Missouri, Iowa and possibly southern 

 Minnesota. The spread of the Colorado Potato beetle, Doryphora 10-Uneata, is a good illus- 

 tration, while the Box Alder bug, Leptocoris trivUtatus, which is slowly but surely making its 

 way eastward, having, as Dr. Fortes informs me, reached eastern Illinois, is another example. 

 Of those that have come up from the far south and fallen into this trend of migration, probably 

 Diabrotica lo)i^icornxs will offer the best illustration, and this will lead me to the discussion of 

 the northward spread of tropical and sub-tropical species. This species was first observed 

 along the eastern slope of the Rocky Mountains, and up to within the last thirty-five years was 

 a comparatively rare insect, found in summer on the blossoms of golden-rod and thistles, and 

 probably occurred, locally, far to the eastward, possibly reaching the Atlantic coast within 

 the last twenty-five years. The writer can well remember when it was of uncommon occurrence 

 in northern Illinois, where now it literally swarms, under certain conditions of Indian corn 

 5 EN. 



