. Bulletin of the Department of Agriculture. Agriculture. 40 BULLETIN 351, r. S. DEPARTMENT OF AGRICULTURE. A third larva, Table XXVI. taken September 1, 1912, at 11 a. m., while in the first day of migration, gave a maximum rate per hour of 101 cm., at 88° F., and an average rate for 2 hours of em. (Fig. 14.) The rate of migration depends both upon the temperature above 70° F. and upon the length of time that has elapsed since the migra- tion started. It is very exceptional for specimens to require more than one day for the twigward migration. Afore than 90 per cent of the females.
. Bulletin of the Department of Agriculture. Agriculture. 40 BULLETIN 351, r. S. DEPARTMENT OF AGRICULTURE. A third larva, Table XXVI. taken September 1, 1912, at 11 a. m., while in the first day of migration, gave a maximum rate per hour of 101 cm., at 88° F., and an average rate for 2 hours of em. (Fig. 14.) The rate of migration depends both upon the temperature above 70° F. and upon the length of time that has elapsed since the migra- tion started. It is very exceptional for specimens to require more than one day for the twigward migration. Afore than 90 per cent of the females. Fig. 14.—Tracing of a female larva of tlie terrapin scale for the first two hours of the twigward migration. Reduced 8 times. Total distance, (Original.) complete this migration during the first 4 hours. Females may occasionally shift to a more favorable position during the second and third days' sojourn upon the twigs, but after this they remain in one place. During the day preceding the twigward migration the female larvse secrete a thin scale which covers the dorsal surface and gives rigidity to the flat, leaf-shaped body. The larvae in migrating pass down the petiole and move along the twigs toward the region of greatest illu-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original United States. Dept. of Agriculture. [Washington, D. C. ?] : The Department : Supt. of Docs. , Govt. Print. Off.
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