A development of a sampling plan for a study of population dynamics of Tuberculoides annulatus Hartig and some aspects of its biology

Abstract

Very little work has been done on arboreal aphids. Available literature on arboreal sampling of insects and studies on biological properties of aphids have been reviewed. The thesis develops a sampling plan for a population dynamics study of T. annulatus and reveals some aspects of its biology.

Selection of the best sampling unit out of clusters and branch tips is described. Timing of sampling, sampling sites, procedures and summary tables of the analyses of variance are given. Occurrence of Myzocallis castanicola Baker in the final sampling is included and an optimum sampling plan has been derived. Ten percent standard error of mean is shown to be an impracticable precision for some stages sampled (especially natural enemies), so a precision of 21% standard error is accepted to be satisfactory for a study of population dynamics of T. annulatus. The necessity to restrict sampling to one site (out of the two studied sites) on basis of precision is discussed.

Several transformations have been tried to select the best fit for selected data. Taylor's power law was the most appropriate transformation. (A FORTRAN computer programme, available for reference at the Department of Entomology, Lincoln College was designed to assist in evaluating the transformation functions based on Taylor's power law.)

Rearing chambers for T. annulatus have been described. Some observations leading to a concept of two, coloured biotypes, in T. annulatus have been discussed.

Feeding behaviour of T. annulatus on the lower epidermis is analysed. The most effective factor driving the aphids to the lower surface is the aphids’ special affinity to lower epidermis.

A modified form of the usual disc technique to study biology of aphids is given. Results obtained on the life history and marked differences in biology of the two colour forms grown on the leaf discs have been discussed.

A study of the growth pattern in one colour biotype of T. annulatus from birth to adult is discussed. A major fluctuation in the breadth, length and weight in the fourth instar is recorded and is accounted for. Correlations between the breadth, length and the weight of instars have been indicated.

The effects of mechanical handling incurred in the proceeding study was analysed and were observed to slow down the rate of development in T. annulatus.