The Dragon-Flies (Odonata) of Illinois; With Descriptions of the Immature Stages. Part I. Petaluridae, Aeschnidae, and Gomphidae

 
9781236353955: The Dragon-Flies (Odonata) of Illinois; With Descriptions of the Immature Stages. Part I. Petaluridae, Aeschnidae, and Gomphidae

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1903 Excerpt: ...of the error is, moreover, continuous throughout the whole series of data, with, however, some probability of variation with the stability of the hydrographic conditions. Finally, the conclusions to be drawn in subsequent pages rest upon data which to a large extent rise above the level of the error resulting from the irregularity of distribution. PLANKTON PRODUCTION. 1894 (Table III., PI. VIII.) Ten collections were made by the oblique-haul method in this year between June 12 and December 15. The volumes of plankton, silt, and total catch per cubic meter average 2.49,.28, and 2.77 cm.' respectively. The maximum catch, 10.18 cm.3 per m.3 (plankton, 9.67; silt,.51) was taken Aug. 15, and the minimum,.25 cm.3 (plankton,.10; silt,.15), on Nov. 11. The series of ten catches form a somewhat regular curve, rising during July and August, and declining, most rapidly in September, to a minimum in October-December. A comparison of the record of 1894 (PI. VIII.) with that of other years (PI. IX.-XII.), as shown in the accompanying table of averages (p. 292), and with the conditions of temperature and hydrograph, will serve to throw light on the significance of the plankton volumes of this first year of our collections. As shown on pages 168 and 164, this wasa year of normally located high and low water, with March, May, and September rises all so reduced as almost to eliminate overflow stages and to prolong low-water stages, resulting in the low average height of 4.63 ft. above low water. Our collections all fall in the stable period, broken only by the September rise. They therefore afford no data on the spring maximum of plankton production, revealing only a single midsummer pulse, culminating in the August maximum in a period of maximum heat and lowest water. In th...

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