The Shipley Collection of Scientific Papers Volume 299
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1889 edition. Excerpt: ...XII of the Report and also on page 250. West of the main Rocky Mountain range the rule of flight appears to be from the higher plains and plateaus, where the insect normally breeds, to the lower and more fertile valleys; and the greater irregularity of the prevailing winds an I more broken nature of the country preclude the same regularity in directions of flight that, on the whole, prevails east of the range. Time of Appearance of invading Swarms.--In endeavoring to deduce general conclusions respecting the time of year that the 1S74 swarms reached different parts of the country, great difficulty was experienced in sifting those accounts which referred to the progeny of the 1873 invasion, and those which hatched within the insect's native range, and came from the extreme Northwest. The same was true of the fresh 187G swarms, and those which hatched in Minnesota. As a rule, the insects which hatch in the temporary region acquire wings and leave before the fresh swarms from the mountain region appear. In the more northern regions, as in Minnesota and Manitoba westward, the insects hatched on the ground acquire wings the latter part of June and in July. The period is earlier as we go south, until in southern Texas thej are able to fly in April. The time of appearance of invading swarms from the permanent region is in inverse ratio, i. e., earlier to the north and later to the south. Thus while on the confines of the permanent region it is almost impossible to distinguish between the insects which hatch there and the fresh swarms from the Northwest, the difference becomes more and more marked toward the south and east. In 1874, swarms appeared during Juno in southern Dakota; during July in Colorado, Nebraska, and Minnesota; during the latter...
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