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The random sampling of cultures of grain weevils

Published online by Cambridge University Press:  10 July 2009

R. W. Howe
Affiliation:
Agricultural Research Council, Pest Infestation Laboratory, Slough, Bucks.

Extract

Four methods have been tested of dividing cultures consisting of wheat grains containing larvae and pupae of Sitophilus granarius (L.) into samples weighing just under 10 g. and suitable for use in fumigation experiments. Two mechanical methods, each dividing a culture into two equal parts, the division being successively repeated to yield 32 samples, were shown to be satisfactory in every trial. One apparatus divided the culture on the chess-board principle, the other by means of radial fins equally spaced round the circumference of a conical divider. The standard method used at the Pest Infestation Laboratory also proved satisfactory; it consists of scooping up samples by hand radially, at random, from a culture dispersed symmetrically by pouring it over the bottom of a spherical flask, but it was evident that personal bias could be introduced by its use. The fourth method, consisting of ‘ random scooping ’, is widely used but yielded samples having considerable heterogeneity from all cultures containing larvae older than the late third instar and having a density exceeding one insect in 30 grains of wheat. This method was the only one that divided standard cultures into samples showing heterogeneity in their age structure. When cultures with an age range of only four days were divided, all four methods yielded samples for which the emergence curves were heterogeneous, apparently as a result of heating induced in samples as small as 9 g. as a result of the metabolism of the larger larvae.

Type
Research Paper
Copyright
Copyright © Cambridge University Press 1963

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References

Adkisson, P. L. (1958). The relative susceptibility of the life history stages of the rice weevil to certain fumigants.—J. econ. Ent. 50 pp. 761764.CrossRefGoogle Scholar
Brown, W. B. (1954). Fumigation with methyl bromide under gas-proof sheets. —Pest Infest. Res. Bull. no. 1, vi + 38 pp. (Revised edition, 1959.)Google Scholar
Howe, R. W. & Oxley, T. A. (1944). The use of carbon dioxide production as a measure of infestation of grain by insects.—Bull. ent. Res. 35 pp. 1122.CrossRefGoogle Scholar
Krause, G. F. & Pedersen, J. R. (1960). Estimating immature populations of rice weevils in wheat by using subsamples.—J. econ. Ent. 53 pp. 215217.CrossRefGoogle Scholar
Krohne, H. E. & Lindgren, D. L. (1958). Susceptibility of life stages of Sitophilus oryza to various fumigants.—J. econ. Ent. 51 pp. 157158.CrossRefGoogle Scholar
Pedersen, J. R. & Brown, R. A. (1960). X-ray microscope to study behavior of internal-infesting grain insects.—J. econ. Ent. 53 pp. 678679.CrossRefGoogle Scholar
Richards, O. W. & Oxley, T. A. (1943). The ejection of frass by larvae of Calandra (Col., Curculionidae) under the influence of CO2.—Proc. R. ent. Soc. Lond. (A) 18 pp. 2224.Google Scholar
Wadley, F. M. (1949). Dosage-mortality correlation with number treated estimated from a parallel sample.—Ann. appl. Biol. 36 pp. 196202.CrossRefGoogle ScholarPubMed