In recent years, the large heath butterfly has undergone a considerable decline throughout much of its European range. In consequence the species is now classified as vulnerable in a European context, although the butterfly is still locally common in northern parts of the United Kingdom. The majority of English colonies are located on expanses of blanket bog in the county of Northumberland, although recent extensive surveys have shown that substantial numbers of colonies have been lost from this area within the last twenty years. C. tullia is one of only four butterfly species with a southern limit to its British distribution, suggesting that climatic change may constitute an additional threat to that faced by many other butterfly species, namely habitat destruction. This thesis consists of an autecological study of C. tullia. Research showed that adult butterflies were most abundant in areas where vegetation was relatively short and sparse. Females oviposited more frequently in short, sparse vegetation than they did elsewhere, suggesting that observed female microdistributions may be consequential of their ovipositional requirements. It is suggested that eggs laid within such areas will experience warmer micro climatic conditions than those laid in taller vegetation, as will resultant larvae. Most sources in literature suggest that large tussocks of the foodplant hare's-tail cotton grass (Eriophorum vaginatum) (L.) are an important requirement of the species. The current study shows that large tussocks are of much lesser importance than previously assumed on sites that are not prone to flooding. The efficacy of heather cutting as a habitat management strategy was investigated. Higher numbers of male butterflies were recorded in cut areas, while the oviposition rates of females within cut areas were higher than in uncut controls. It is therefore suggested that heather cutting renders overgrown habitat more suitable for adult butterflies, and would therefore constitute an effective conservation management strategy on certain sites.The mobility of adult butterflies was investigated. Males were found to move for greater distances than females, and were found to be capable of dispersion between sites separated by 500m of unsuitable habitat. Females were found to be extremely sedentary, and no between-site movements were detected. It is therefore suggested that gene flow between populations at Border Mire sites is probable, although colonisation of remote sites is not. A series of absolute population estimates were made at three study sites. These data were significantly related to same-day relative estimates made using transect counts, although the relationship was not sufficiently close to confidently predict absolute values from transect counts alone. However, were more time devoted to a similar study, it is probable that this outcome could be achieved. The annual abundance at each site was calculated for each of the flight periods 1999-2001 inclusive. A life table study, investigating mortality in the pre-adult phases, was undertaken. Essentially, this study revealed that egg mortality and pupal mortality rates were both low, while larval mortality, particularly of the first instar was relatively high. Causes of mortality were not confirmed. Dissection of freshly emerged females suggested that females are probably capable of producing 65-90 eggs during their lifetimes. Adult feeding behaviour was studied. The preferred nectar source of both sexes was cross-leaved heath (Erica tetralix) (L.), although other nectar sources were also used. A study of post-copulatory behaviour revealed that females commenced oviposition prior to feeding. The importance of nectar to the butterfly was investigated by means of a trial using captive female butterflies. A group of females provided with food in the form of sucrose solution produced a similar number of eggs to a group of identical size provided only with water, suggesting that nectar availability is of less importance than has been shown for some other butterfly species.

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The Common blue butterfly, Polyommatus icarus (Rott,) , is widespread throughout its Palaearctic distribution and persists in areas with differing climatic conditions. It is known to be a highly variable butterfly with marked within and between population variation in morphology, thermal biology, and voltinism. These traits together with allozymes and a neutral DNA marker (AFLP) variation are studied here to understand how geographic trait variation is related to environmental variation. The approach adopted here is to study this along a latitudinal cline of temperature and photoperiod, using four populations from south to north within mainland Britain. AFLP differences, but not allozyme variation, indicate genetic structuring, with an isolation by distance effect. Enzyme diversity of P. icarus butterflies in the British Isles is lower than on mainland Europe, indicative of a past bottleneck. This, combined with selection on, or drift in, the allozymes could cause for a lack of population structure in this marker. Despite high levels of gene flow between populations, local adaptation is possible, as differentiation in certain allozyme loci was found (PGM and PGI). Populations differed in their response to developmental cues. Northern populations have an obligate diapause strategy and southern populations' development times differ in response to temperature, indicating local variation in response to environmental conditions. Populations differed in wing morphology (size, shape and melanisation) but this was not related to latitude. Experimental determination of heating rates in different basking positions and thoracic temperature at take-off revealed no strong relationships of the morphological characteristics with heating or cooling rates and an indication of relationship with PGI alleles. It is suggested that m comparison to larger butterflies morphological variation IS unconstrained by thermal requirements. The persistence and widespread occurrence of this butterfly may be a consequence of the variability of traits within this butterfly.

Arid environments are resource-limited, with scarcity of water the key limiting factor for plants and their associated fauna. Consequentially bottom-up forces often control food webs, influencing the whole system through high levels of competition. The Sinai Baton Blue butterfly, Pseudophilotes sinaicus, is Critically Endangered, with a tiny endemic distribution in the St Katherine Protectorate, South Sinai, an arid environment. Its range is restricted to that of its sole host plant, the near-endemic endangered Sinai Thyme, Thymus decussatus, leaving the butterfly in a highly fragmented distribution. This study looks into the spatio-temporal variations in quality and abundance of the host plant and its implications for the Sinai Baton Blue. Over the past decade the butterfly has exhibited severe population cycles, with the causes still unclear; it could be due to the fluctuating resource levels with large temporal variation in the quality of thyme and density of inflorescences. The number of flowers significantly influences the larval distribution, indicating that resources play a key role in offspring survivorship. Population viability analysis has also highlighted the importance of management techniques aimed at increasing the butterfly's survivorship. The butterfly population sizes are positively correlated with the total resource area and the number of host plants but not the distance between habitat patches. Population viability analysis also suggests that habitat area is more influential than connectivity in this system driving current dynamics. Overall this project has highlighted the urgent need for conservation focused on improving plant quality within patches in order to save this fragile species.