The thesis answers the general question of whether the quality of artificially reared insect species should be based on performance tests for intended use or whether quality should be based on a more holistic biological approach. The empirical research is carried out using the lepidopteran leafroller 'Cnephasia' jactatana (Walker). The thesis defines biological performance and quality in terms of the success of an insect population in survival and reproduction and regards the laboratory environment as an artificial habitat that insects must colonise in order to survive and reproduce. Changes in biological performance that occurred during 12 successive generations of laboratory rearing were due to selection, acclimatisation and domestication and not adaptation. Artificial colonisation is theoretically successful within a limited range of environmental factors. As the inherent genetic variability of the founder population determines the resilience of the population to changes in performance, the ranges of environmental factors during colonisation should be wide to 'capture' much of the variability. Using body size (weight) as an aspect of overall quality, the thesis presents evidence that the final instar larva of C. jactatana has a threshold mechanism (larval critical weight, LCW) that determines pupal and adult size. There is a proportionate decrease in weight from the maximum weight that a larva attains in the final instar (LMW) to pupa ( described as constant DP ) and to adult (DA). There is a direct relation between the latent feeding period (period between attaining an LCW and LMW), LMW, pupal and adult size, and the reproductive performance (fecundity ). Within the experimental conditions diet quality, temperature, photoperiod and artificial selection had no effect on the larval critical weight, DP or DA, the larval threshold mechanism in C. jactatana is probably a mechanical trigger that initiates pupation. Diet quality, temperature and thermophotoperiods affected pupal size, adult size and reproductive performance. Photoperiod had no significant effects on size and reproductive performance. Positive assortative selections for slow development and low pupal weight significantly decreased pupal and adult size, and reproductive performance. Selection for fast development and heavy pupal weight for three generations had no significant effect on size or reproductive performance. Larval critical weight is demonstrated as useful to define quality indices and predict the performance of laboratory reared insects. The general conclusion of the thesis is that insect quality should be defined more in terms of the success in survival and colonising ability rather than solely on the success for 'intended role' or 'fitness for use'.

Historical background: Study of plankton communities of New Zealand waters has been neglected in the past. The various expeditions which have collected in the area have mostly concentrated on dredging, shore collecting and bathypelagic programmes. Even the earliest expeditions, dateing from the voyages of Cook, recorded superficial observations of plankton organisms. However, the first serious observations were the descriptions by Dana (1850's), of pelagic crustaceans from the collections of the U.S. Exploring Expeditions (1840). Then in the winter of 1874, H.M.S. "Challenger" made a number of tow-nettings in the Tasman Sea and the reports of the expedition together comprise the first comprehensive account of the plankton of the area.

The genus Ctenopseustis Meyrick (Lepidoptera: Tortricidae) is reviewed and the type species C. obliquana (Walker) is redefined. The species C. servana Walker and C. fraterna Philpott are reinstated and the synonomy and characteristics of each species are described and illustrated. Populations of the three leafroller species Epiphyas postvittana (Walker), C. obliquana and Planotortrix excessana (Walker) together with Stathmopoda “skelloni” (Butler) were monitored intensively from 1976 to 1979 in an insecticide free block of mature apple, cv ‘Dougherty’ trees in West Auckland. S "skelloni" is recorded as a pest of apple for the first time. The general biology, distribution and host range of these four species is described. A key to the larvae of the four species, as found on ‘Dougherty’, using head capsule measurements together with other characters, and keys to the leafroller eggs and pupae are provided. A technique to successfully mate C. obliquana and P. excessana in the laboratory was formulated by predicting the emergence time of female pupae and enclosing one such pupa with several males. A colony of C. obliquana was initiated from the progeny of a single mated female but collapsed in the fourth generation and possible reasons for this are discussed. The life history of all four species on ‘Dougherty’ apple in Auckland is described. E. postvittana completed four generations, P. excessana three and S. “skelloni” two but the number of C. obliquana generations per year was undetermined. The seasonal and daily flight periods were determined using two suction traps within the apple block. Female flight in all species occurred shortly after sunset, generally for two to three hours, whereas male flight extended for up to eight hours after sunset. Results of the suction traps were also used to show the lower temperature thresholds of flight for E. postvittana as 7-8°C, 8-9°C, and 10-11°C for the second summer, spring and first summer generations respectively and for S. “skelloni” as 9-10°C and 11-12°C for the autumn – winter and spring –summer generations respectively. Loss through pre-establishment failure of first instar larvae accounted for the greatest amount of mortality in the life history of all leafroller species. No eggs or pupae of S. “skelloni” were found on the trees throughout the study. Egg mortality in the leafrollers was low and larval parasitism was up to 33.6% in E. postvittana and 19.6% in P. excessana. The parasite species found associated with each leafroller host are listed, the most common being Apanteles tasmanica in E. postvittana and Goniozus sp. in P. excessana. Host preferences were shown by several parasite species. Parasitism of E. postvittana by Apanteles spp. reduced the larval growth rate and head capsule size of this leafroller. Larvae of C. obliquana did not complete development on the 'Dougherty’ trees due to its resistance to this leafroller species. Laboratory rearing experiments comfirmed this and showed cv 'Red Delicious’ was susceptible. A third culivar, 'Granny Smith’, showed some indication of resistence to the larvae of C. obliquana and P. excessana but E. postvittana showed high survival rates on all three cultivars. The distribution of each species within both the study site and the trees was examined. S. “skelloni” showed a significant preference for the calyx of fruit whereas all leafroller species preferred feeding sites on the foliage. Analysis of instar – feeding site comparisons showed that leafroller larvae moved to new feeding sites several times in their lives. S. “skelloni” probably remained in their initial sites until leaving the trees to pupate.

The aim of this study is to test for photoperiodic control of larval and pupal development in the New Zealand moth Planotortrix octo Dugdale. The photoperiodic response curves for larval and pupal development and especially for instar number at 17°C and 21°C indicate that a photoperiodic mechanism is involved. Superimposed on this response is the suggestion that daylength affects development rate directly, with larvae and pupae developing faster under longer photophases. This effect is especially strong for pupal development (Chapter 3). The effects of thermophotoperiods (Chapter 4), night interruption and resonance experiments (Chapter 6) provide further evidence for photoperiodic involvement. The response to resonance experiments suggests the involvement of an hourglass rather than a circadian mechanism. Larvae reared under short days accumulate significantly more lipids in the 5th and 6th instars than larvae reared under long days (Chapter 4). This finding, combined with the suppressed development rate and higher instar number under short days, suggests that a weak form of diapause may be present in this insect. This is significant in being the first recorded incidence of a photoperiodically induced diapause in a phyllophagous New Zealand insect for which a year round food supply is available (Chapter 1). By transferring insects from long to short days I found that long days have more influence than short days on larval development (Chapter 7). An attempt was made to measure juvenile hormone titres under long and short days using a Galleria bioassay. The test used was not sensitive enough however to measure any significant amounts of juvenile hormone (Chapter 8). Simulations of the experimental results were performed using a damped circadian oscillator model (Chapter 9). This model was considered the most appropriate to use, based on the experimental results and on a review of the literature (Chapter 2). Simulations showed good similarities with experimental results in most cases, but could not account for resonance responses.

In insects, olfaction is mediated by a large family of integral membrane proteins, called olfactory receptors (ORs), that mediate the transduction of odorant binding into a neuronal signal. A functional assay for insect ORs was developed utilising calcium imaging in Sf9 cells. The Drosophila melanogaster OR, Or22a, was expressed using transient transfection, and its activity measured by monitoring increased intracellular calcium levels using a calcium–sensitive dye. The interaction of the odorants ethyl butyrate, pentyl acetate and ethyl acetate with Or22a were both dose–dependent and sensitive, with EC50 values of 1.53 x 10−11 M, 5.61 x 10−10 M and 3.72 x 10−9 M, respectively. Furthermore, Or22a expressed in Sf9 cells has a similar response profile to a range of odorants previously tested in vivo. This assay system will provide a useful tool for the investigation of insect olfactory receptor structure and function. A consensus of eleven transmembrane (TM) domain prediction algorithms suggested a model for Or22a that contains seven TM domains, reminiscent of GPCRs. To test this model empirically, the membrane topology of Or22a was determined using epitope–tagging of predicted loops followed by immunochemistry. These experiments revealed that Or22a has seven TM domains but that its orientation in the membrane is opposite to that of GPCRs, having a cytoplasmic N–terminus. This orientation was also observed for Epiphyas postvittana Or1, which suggests that this inverted topology may be common to all insect ORs. To test whether Or22a forms higher order structures, fluorescence resonance energy transfer (FRET) between cyan and yellow fluorescent proteins inserted into the intracellular loops of Or22a was employed. The third intracellular loop interacts strongly with itself in homo–multimers, with interactions between the first and first loops and first and third loops also observed. These experiments show that ligand binding ORs can form multimeric structures in heterologous cells. The co–transfection of Or83b into S2 cells had no impact on these interactions, however Or83b is likely expressed in this cell line. Finally, models of how a ligand binding OR interacts physically with the ion channel Or83b are presented, and approaches that could be used to distinguish between these models are discussed.

Invasive ant species represent a major threat to biodiversity through their detrimental impacts on native ecosystems. An important step to managing invasive ant species is determining the factors responsible for their current and potential distribution. This thesis examines the spatial distribution of invasive ant species at a range of scales. The focus is on the Pacific region, specifically Fiji and New Zealand, which have a relatively high number of invasive ant species. Taxonomic checklists of the ant fauna of Fiji and New Zealand are presented. Climate variables were used to model the distribution of, and predict suitable areas for, particular invasive ant species. In general, models had high evaluation success, especially for models that were built and tested within a region. However, the utility of models was far less when transferred and tested in new regions. A better understanding of how climate variables directly and indirectly affect a species is needed to improve the utility of species distribution modeling. On a finer spatial scale, habitat partitioning was evident at Colo-i-Suva Park in Fiji, where distinct ant communities were sampled from litter and canopy habitats. Results suggested that body size, habitat and resource utilisation interact to create opportunities for invasion, and influence the susceptibility of different habitats. Habitat also shaped the assembly of ant communities and mediated inter-specific competition in the Yasawa Islands, Fiji. Similarly, habitat was important in partitioning ant communities in New Zealand; endemic ant species were in forest, and invasive species in scrub and urban habitats. However, there was no evidence that inter-specific competition influenced community composition or the distribution of invasive ant species at regional or local scales in New Zealand. The extent and diversity of exotic ant species arriving at the New Zealand border was also investigated. A high proportion (>64%) of intercepted ants originated from the Pacific. The effectiveness of detecting exotic ant species at the New Zealand border ranged from 48-78% for different pathways, indicating a number of species remain undetected. Future work on invasive ants should focus on species-specific tolerances, and how the physical environment and small scale abiotic conditions influence distribution.

In insects, olfaction is mediated by a large family of integral membrane proteins, called olfactory receptors (ORs), that mediate the transduction of odorant binding into a neuronal signal. A functional assay for insect ORs was developed utilising calcium imaging in Sf9 cells. The Drosophila melanogaster OR, Or22a, was expressed using transient transfection, and its activity measured by monitoring increased intracellular calcium levels using a calcium–sensitive dye. The interaction of the odorants ethyl butyrate, pentyl acetate and ethyl acetate with Or22a were both dose–dependent and sensitive, with EC50 values of 1.53 x 10−11 M, 5.61 x 10−10 M and 3.72 x 10−9 M, respectively. Furthermore, Or22a expressed in Sf9 cells has a similar response profile to a range of odorants previously tested in vivo. This assay system will provide a useful tool for the investigation of insect olfactory receptor structure and function. A consensus of eleven transmembrane (TM) domain prediction algorithms suggested a model for Or22a that contains seven TM domains, reminiscent of GPCRs. To test this model empirically, the membrane topology of Or22a was determined using epitope–tagging of predicted loops followed by immunochemistry. These experiments revealed that Or22a has seven TM domains but that its orientation in the membrane is opposite to that of GPCRs, having a cytoplasmic N–terminus. This orientation was also observed for Epiphyas postvittana Or1, which suggests that this inverted topology may be common to all insect ORs. To test whether Or22a forms higher order structures, fluorescence resonance energy transfer (FRET) between cyan and yellow fluorescent proteins inserted into the intracellular loops of Or22a was employed. The third intracellular loop interacts strongly with itself in homo–multimers, with interactions between the first and first loops and first and third loops also observed. These experiments show that ligand binding ORs can form multimeric structures in heterologous cells. The co–transfection of Or83b into S2 cells had no impact on these interactions, however Or83b is likely expressed in this cell line. Finally, models of how a ligand binding OR interacts physically with the ion channel Or83b are presented, and approaches that could be used to distinguish between these models are discussed.

The Australian sheep blow fly Lucilia cuprina is an economically important dipteran pest whose circadian behavioural rhythms have been the subject of considerable scrutiny. The underlying biochemical nature of these rhythms however, has remained a mystery. The primary objective of this thesis was therefore to investigate the molecular control of circadian rhythms in L. cuprina using an integrative approach. To these ends, a dynamic molecular simulation model for L. cuprina was formulated using existing biochemical data on insect circadian clocks. The validity of this simulation model was subsequently tested at both molecular and behavioural levels. The basic molecular assumptions of the simulation model were tested by cloning a full length L. cuprina per cDNA and analysing its mRNA and protein expression levels. Isolation of the 4 Kb L. cuprina per cDNA revealed the conservation of three functional domains known to be important for circadian clock function; namely the PAS dimerisation motif (with 92% identity to D. melanogaster at the amino acid level), and the cytoplasmic and nuclear localisation domains (with 85% and 80% identity respectively). A fourth domain, the threonine-glycine (TG) repeat region, was also found to be conserved, but severely truncated in L. cuprina. No length variation was found in the TG repeat of flies collected from several different latitudinal zones, and no correlation was detected between sequences flanking the repeat and latitude of collection of flies. Thus, the contention that the TG repeat region plays a role in temperature compensation of the circadian clock is cast in doubt. Expression analyses (using quantitative RT-PCR) showed per mRNA levels to undergo diel oscillations with a period (24 h) and peak phase (Zt 12) consistent with the Drosophila data. PER-immunoreactive protein oscillations were also demonstrated, with peak immunoreactivity lagging approximately 3 h behind peak mRNA levels. The behavioural predictions of the model were tested by recording adult locomotor activity under different light regimes. The simulation model successfully predicted free-run, entrainment, the effect of short light pulses, and the effects of constant lighting on behavioural rhythms. Disparities between the simulated and real phase response cnrves for L. cuprina are hypothesised to be indicative of an ealier nuclear entry time of the PER-TIM dimer in L. cuprina compared with D. melanogaster. The three different approaches of simulation modellingo molecular analysis and behavioural investigation are integrated in the discussion in order to help provide a comprehensive explanation of circadian function in L. cuprina. The benefits of an integrated approach to the analysis of circadian function are discussed, as is the relevance of the present findings to the development of a clock-based control strategy for this economically important pest species.

The species status and host range of Heliothis armigera was investigated. DNA profiling, mitochondrial DNA sequencing, RAPD's, along with traditional morphological and crossing methods were used to investigate micro, macro and mega-population structuring. Thirty-six new host records were added, of which a number are important common weeds and crops. Mortality due to parasitoids and fungal infections were quantified on many host species. Genetic analysis of the COII and the AT-rich regions of the mitochondrial DNA showed very high levels of variation, as did the DNA profiling using the probes (CA)n and 33.15. The morphological analyses also showed variation, but to a lesser degree and without statistical significance. The variation found at all levels and in all aspects is discussed with respect to caterpillar host-plants and geographical location. All host-plant populations of caterpillars showed very high levels of genetic variability. However, the population of caterpillars found on Sulla (Hedysarium coronarium) was significantly more variable than those found on Lotus and Lucerne when compared using DNA profiling. The sequences obtained from the two mtDNA regions also showed considerable variation, a great percentage of which was uninformative. This variation did not allude to any structuring of caterpillar populations with respect to host-plant or geographical location. H. armigera is genetically a very variable species which does not equate with any population structuring present in the host-plant or geographical populations investigated here. This study has greatly increased the general understanding of this insect, and has elucidated a portion of the genetic makeup, but not helped in the development any new control methods.

Although Argentine ant(Linepithema humile), a highly invasive ant species, has been in New Zealand for at least l4 years, little is known about their ecology and potential for invasion. Increasing spread and establishment of populations throughout New Zealand is disturbing because of the devastating impacts documented on native invertebrate biodiversity overseas. The primary aim of this study was to determine the impacts of Argentine ants on arthropods in native forest habitats in west Auckland. Pitfall traps at invaded and uninvaded sites were used to quantify ant and non-ant arthropod faunas. Argentine ants did not adversely affect native host ant communities. Moreover, two ant species appeared to be resistant to invasion. Argentine ant invasion reduced the abundance of a few orders of invertebrates while several taxa were more abundant in the presence of Argentine ants. Distribution and foraging activity of Argentine ant populations were monitored in this study from 2000-2003. Also, rate of spread was investigated to evaluate whether native forest habitats would be at risk from invasion. Measurements of foraging ant trails on monitored tree trunks revealed seasonal distribution patterns involving high activity in summer/autumn and low activity in winter/early spring. Argentine ants were found to be established primarily along the edge of the forest and did not invade into the interior of the forest during the study period. An Argentine ant poisoning operation on Tiritiri Matangi Island in January 2001 provided the opportunity to document the results of the eradication trial. In addition, pitfall traps placed at two treated sites and one untreated site were used to compare pre-poison and post-poison effects on ant and non-ant invertebrate communities. Fipronil baiting at 0.01% effectively reduced Argentine ants at the study sites and very few ants were observed in both tree count and pitfall trap recordings two months after poisoning. The invasion of Argentine ants on Tiritiri Matangi Island decimated native host ants and no recovery was detected throughout the study. Several groups of invertebrates appeared to benefit from the removal of Argentine ants while a few showed no detectable changes. Conservation implications resulting from the findings of this study are discussed Also, potential future research involving Argentine ants are outlined.