Investigation into aspects of the biology of tubular black thrips, Haplothrips victoriensis Bagnall (Thysanoptera: Phlaeothripidae) in South Australia.

Abstract

Haplothrips victoriensis Bagnall (Thysanoptera: Phlaeothripidae) is an indigenous thrips of southern Australia. It is known as a predator of two-spotted mite. This project investigated various biological characteristics of H. victoriensis as a precursor to its potential use in biological control. In addition, H. victoriensis is very difficult to distinguish from other Haplothrips species in terms of morphology, especially as there are no keys to larvae. DNA barcoding and morphology of the larval stages are used to address these issues. The thesis is divided into seven chapters comprising an introduction, four main research chapters, conclusion and reference chapters. Chapter 2 covers the culturing techniques for H. victoriensis. Some new cases and rearing processes were designed to culture H. victoriensis and its prey. These were following series of rearing techniques investigated including rearing H. victoriensis for egg collection, H. victoriensis larvae and adults for biological and morphological observations, mass rearing of H. victoriensis, WFT and Tyrophagus mites, and rearing WFT for egg collection. Predatory H. victoriensis was reared in the laboratory with various diets of honey, pollen, Tyrophagus mites and western flower thrips (WFT). Chapter 3 investigates the biological development of H. victoriensis, including egg, larva, prepupa, pupa and adult stages. Haplothrips victoriensis fed with 10% honey solution, mixed pollen and Tyrophagus eggs took about 16-22 days to develop from eggs to adults at 25 oC. Developmental times of immature H. victoriensis varied when fed on different food sources. The longevity of H. victoriensis was significantly different with different diets. Chapter 4 examines predatory and cannibalistic characteristics and consumption of H. victoriensis on various prey. Haplothrips victoriensis was found to feed on many kinds of common prey; Two spotted mite (TSM), Tyrophagus mite, WFT, spotted alfalfa aphid, greenhouse whitefly and diamond back moth but not on ash whitefly. Importantly, H. victoriensis was also found to be cannibalistic which might affect population fluctuations in the laboratory and in the field. Chapter 5 examines the ecology and hosts of H. victoriensis in South Australia and taxonomy of H. victoriensis and some other Haplothrips species being similar to H. victoriensis. Haplothrips victoriensis was found to live on flowers from a range of different plant families. Morphological characteristics of the immature stages of H. victoriensis and a key developed to separate common Haplothrips in S.A. As well, COI was used to possibly identify H. victoriensis and its morphologically similar taxa and investigate whether H. victoriensis is a single species or perhaps contains cryptic species. None of the specimens of H. victoriensis included in the analyses showed any variation in COI indicating a single species for horticultural areas in S.A. Chapter 6 provides an overall discussion of the main results and indicates areas of future research.