Page:The Scientific Monthly vol. 3.djvu/233

 INSECT MIGRATION 227

��^^:ect migrations as eelated to those of birds

���By HOWARD J. SHANNON

JAMAICA, N. Y.

��OST of us know that many great flight-ways of migratory birds have been accurately mapped out both on the European conti- ^^SXit and on our own. But no systematic attempt has ever been made to determine the flight-lines of migratory insects. In fact, it has hardly been suggested that such lines of travel exist. Significant move- ments, however, observed by the writer while stationed upon the southern Long Island coast seemed to indicate that both " monarch " butterflies as well as certain dragonflies habitually travel westward along that i'hore, and for many autumnal days in succession, in an apparent at- tempt to reach the mainland and an overland southward route to the tropic zone. These studies then not only suggested the theory that both insects were true seasonal migrants like birds, but also that similar arenuos of travel must exist in other parts of the country. This conclu- sion lijis been strikingly upheld by further explorations. For, from ad- clitional evidence gathered in the field and by means of an extensile w>rrespondence, it now becomes possible to define some of the principal insect highways of eastern Xorth America. These should become the ^^is for the study of what is virtually a new science — the bionomics Seasonal insect migrations.

One such route, evidently extends along the eastern coast from the

^•'' Canadian territory to the Gulf States. For, although the Maine-


 * ^^8t record of a " monarch '' flight is the most northerly that has been

^ported, many of these migrants must be directed to these natural

,^^h\^ays soon after leaving their summer habitat in the farther north.

■^^*^h this record and most others reported along the seaboard are de-

^^i*ibed as "butterfly processions" faithfully following the trend of the

^^^I'e whatever its local direction. For they even turn westward along

^■^^ Connecticut shore of the Sound (as recently observed by the writer),

^^d beautifully parallel their similar coastwise behavior on the southern

^oixg Island ocean coast.

In both cases, of course, they are bound for New Jerst^y; and

thence continue southward until the waters of Chesapeake Bay seem

\fl cause a partial, sidewise diversion. For a great swarm, moving at

^ considerable elevation, was seen in the year 1886, flying southward

near the headwaters at West River, Maryland, which is situated far

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