Although the word 'population' originally referred to people, biologists have since used it to embrace the numbers of any plant or animal species and statisticians have further extended its application to inanimate objects. Biologists in general, but ecologists in particular, tend to recognise four major properties of populations . (1) . They consist of a number of individuals , (2) . There is a likeness of kind among these individuals . (3) . There i s a criterion of 'aliveness', (4) . The individuals are limited in space and time.

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Aspects of the ecology of the moth Coleophora alticolella have been investigated at a low-altitude site on the Cumbrian coast (15m above sea-level) and along a transect from 215m to 610m on the western escarpment of the northern Pennines. The larvae of this moth feed on the seeds of the rush Juncus sguarrosus. Seed production by the food-plant is reduced at higher altitudes, where the climate is severe. The oviposition period is delayed with increasing altitude and the eggs are laid singly, if there are sufficient oviposition sites on the developing inflorescences. Survival of the larvae, between hatching and establishment inside the food supply, is directly related to the proportion of J. squarrosus florets developing into seed capsules. Consequently, as a result of the progressive reduction in seed capsule production with increasing altitude, there is greater mortality during larval establishment at the higher sites. Larval case production and subsequent migration to overwinter in the leaf- litter are both retarded with increasing altitude, provided that the food supply is adequate. Both the number of species of parasitic Hyraenoptera, attacking the larvae, and the percentage parasitization are reduced with increasing altitude. .Hyperparasitoids were present at the lowest site. Starvation of the larvae, as a result of the reduced J. sguarrosus seed production, was the most important mortality factor in the population dynamics of Coleophora alticolella at the highest altitudes. Parasitoids controlled the population at the lowest altitude. Between these two extremes, competition for food by the fourth instar larvae is most important. This acts as a density-dependent factor, reducing natality in the following spring. The larvae often eat all of the seeds produced by the food-plant in this middle region, but not at sites of higher or lower altitude.

Most biological diversity is concentrated in the tropics and represented by insects, but threatened species programmes were created for and concentrate on vertebrates. Unfortunately, there is an impediment to the conservation of tropical insects resulting from issues with taxonomy, quality of data and resources available. Butterflies, among insects, are one of the most suitable organisms for conservation studies. The first goal of this research was to examine the feasibility of assessing the threat status of Neotropical butterflies using IUCN criteria. Recently, an index using Red List data has been developed by IUCN to evaluate trends in threats to hyper-diverse groups based on a random sample of species. IUCN Red List threat assessments were undertaken by collating available locality data from various sources and modelling species ranges using BIOCLIM within DIVA-GIS. Following this approach, 631 Neotropical butterfly species were selected from the sample of 1500 world species. Threat assessments were carried out for 336 species in three families from which suitable data were available, and a preliminary list of Key Biodiversity Areas for butterflies was identified. Distribution ranges were modelled, then compared to land use changes to evaluate habitat loss. A total of 23 butterfly species were categorised as Vulnerable and 3 Endangered, with the rest as Least Concern. Only 7.7% of species were found to be threatened, a relatively low proportion compared to other groups, but this seems likely to be an underestimate of the real threats facing this group. In order to explore this issue, a systematic review of the genus Splendeuptychia (Nymphalidae: Satyrinae) was undertaken. This genus is polyphyletic and was found to comprise at least four genera of which that containing the type species of Splendeuptychia was studied further. Once unnamed taxa and several cryptic species were recognised, the number of species-level taxa in this group increased significantly, as did the number of threatened species because species with restricted ranges were taxonomically overlooked. This study highlights the importance of detailed systematic research to achieve effective biodiversity conservation.

Olfaction is a vital sense that informs moths of their environment, and as such moths are adept at chemical sensing. Natural odours are often complex mixtures of different compounds. Thus, odour components can interact along the olfactory pathway in a nonlinear fashion such that the mixture is not perceived simply as the sum of its components. Here an investigation is made into possible nonlinear interactions in the olfactory system of moths at two stages along the olfactory pathway. These are the input to and the output from the antennal lobe, the region of the insect brain responsible for the first neural processing of odour information.;The input to the antennal lobes is the neural representation of odours carried by the receptor neurons. By use of a calcium sensitive dye, this activity was observed optically as odour-evoked changes in Ca2+ concentration in the moth Spodoptera littoralis. This reveals the input pattern to functionally distinct neuropil in the antennal lobes, the so-called glomeruli. Such a calcium imaging analysis requires the identification of the glomeruli, and a novel method was developed to facilitate the automatic identification of olfactory glomeruli. By applying unsupervised clustering analysis to sets of calcium images, glomeruli were functionally identified. Binary odour blend responses were then analysed for nonlinear interactions, but no strong interactions were found.;The output from the antennal lobe, the projection neuron responses, was assessed by computational models. It was demonstrated in pheromone processing models that a spatiotemporal odour code is better able to encode for blend ratios than a spatial code. And it was shown that a spatiotemporal general odour model produces nonlinear component interactions, despite the data-motivated input having none.

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Long term monitoring has revealed that butterfly populations vary dramatically between years, among sites and across species. This PhD investigates the importance of biotic and abiotic resources in determining butterfly abundance at multiple scales, using long term data from intensive studies on the Glanville fritillary and from the extensive UK Butterfly Monitoring Scheme. The most important resource at local scales is the ‘suitability’ of the larval hostplant: only plants within a certain temperature range are likely to be utilised for oviposition. Laying eggs on warmer plants maximises the probability of successful larval development within restricted seasonal temperature constraints. Analysis of Glanville fritillary population time-series reveals that populations are more abundant in those habitat types providing suitable microclimates for larval development, and in years following warm spring temperatures (i.e. during oviposition). These factors were also important when comparing abundance across sites, as were patch area and isolation. This landscape-scale analysis also revealed a significant negative interaction between habitat quality and temperature, suggesting that microsites for oviposition are less restricted in warm than cool years. Across regional scales (southeast England), the availability of both host and nectar plants are important in determining butterfly abundance, both across and within species. However, hostplant availability is a stronger predictor of abundance than nectar, and is most pronounced on sites with a northerly aspect. Trait analysis revealed that species with restricted diets, low mobility and habitat specialism are most sensitive to variation in foodplant availability. Taken together, the results suggest that many UK butterfly species are limited at small scales by the availability of hostplants in warm microclimates, but at large scales by dispersal limitation and climatic tolerance. Site management can therefore increase the abundance of key species of conservation concern by creating thermally diverse habitats and maximising the biomass of their hostplants.

The biology and behaviour of Bphestia calidella and E.figulilella were studied in the laboratory, and a comparison made with the biology of the closely related storage pest E.cautella, and the pre-harvest species, Ectomyelois ceratoniae. Factors affecting the laboratory rearing of each species were investigated, and improvements in existing culture methods described. Ectomyelois required greater space for mating than the other species, and its requirements for light were more critical. Fluctuating temperature and humidity, and air-circulation inside the mating cage also improved fertility. A laboratory stock of Ephestia cautella, reared under constant conditions for four years, was less fertile and less adaptable to changes in rearing conditions than a fresh warehouse stock. The effects of constant temperature and humidity, and different light regimes on the development of each species were studied. Optimum conditions for development for all species were 30°C. 70%r.h. and between 14L/10D and 16L/8D photoperiod. Ephestia calidella, E.figulilella and Ectomyelois exhibited a larval diapause induced by short-day photoperiods. Exposures to carbon dioxide and long-day photoperiods were used to terminate diapause in Ephestia calidella. The suitability of various natural and semi-artificial diets was assessed. E.cautella was the most successful species on stored foodstuffs, and Ectomyelois the least successful. Diets rich in glucose and glycerol were more suitable for Ephestia figulilella and E.cautella than for the other species. Differences in chorion microstructure were studied under the scanning electron microscope, and their use in the identification of Phycitids considered. The adaptation of each species to its particular habitat was discussed. Ectomyelois was less able to colonize the storage environment than the other species because of its food, light and space requirements. Ephestia calidella and E. figulilella were found to have considerable potential as storage pests.