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The work described in this thesis was designed to throw some light on the problems of the larval behaviour and way of life of the British Hydracarina. Although these animals are a common and numerous element in nearly all fresh-water habitats the full life-histories are known for very few. The principal method of investigation used in this work was by catching and examining aquatic invertebrates and attempting to identify any mite larvae which they were carrying. The lack of any complete key made it necessary to attempt to breed these larvae through to the adult stage and this was done successfully in five cases. The hosts for a further three species were found by using larvae bred in the laboratory to produce parasitic infections of hosts under experimental conditions, while another seven species of larva were identified on the host from Sparing's key and by comparison with bred specimens. The actual transfer of the larvae onto their hosts was observed for an Arrenurus species, parasitic on Zygopteran adults, and for Protzia eximia, Protz, whose larvae jump distances of up to 2 cm. from the water or land surface to reach their positions on their Empid or Trichopteran hosts. The larvae of two Unionicola spp, believed since the time of Bonz, 1783 to be free-living, were shown to be parasitic on Chironomids, thus making the position of the Unionicolidae in the Super-family Pionae much more comprehensible than it had hitherto appeared. Collections of large numbers of Chironomids showed the great importance of this group in the life cycles of the Hydracarina, and it also became obvious that the Nematocera in general appear to be by far the most important host group for the water-mites. In the appendix are descriptions of three previously unknown larvae together with a table summarising present knowledge of the hosts of water-mites.

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This thesis addresses the life-history strategies of cursorial riparian spiders using field- and laboratory-based research. Species distributions were compared to important habitat variables with particular reference to disturbance. The nature of a "habitat templet" for riparian spiders was also examined. No 'typical' riparian spider fauna was identified. Most dominant species were opportunistic aeronauts, associated with disturbed habitats. Disturbance accounted for little variation in distributions. This is attributed to all sites being disturbed, with the actual frequency of flooding having little influence. Light penetration, the proportion of sand in the substrate, amount of exposed substrate and leaf-litter depth all significantly influenced the distribution of spiders. The influence of disturbance on the life-history traits of two congeneric and co-habiting lycosids (Paradosa argicola and P. amentata) was examined using manipulated levels of flooding. This showed that both species have evolved different strategies to cope with the consequences of flooding. P. amentata, a widespread generalist, had more plastic development periods and instar sizes across different treatments. Traits of P. agricola, a habitat specialist, were not plastic and this species has evolved a greater tolerance to flooding. Examination of the reproductive strategies of P. agricola and P. amentata revealed that both species can adjust their reproductive output. Both species produced smaller clutches later in the season. Offspring of these clutches had larger instars and shorter development periods, which is assumed to increase juvenile survival in conditions of greater environmental stress. No trade-off existed between the numbers and sizes of eggs within clutches. Maternal body size, however, was positively associated with clutch size and weight. Maternal size had no influence on egg sizes.

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This work is focused on structural studies of the innate immune protein α2-macroglobulin from the horseshoe crab, Limulus Polyphemus, using crystallography and structure prediction software to reveal clues about the structure and function of this key immune mediator. The α2-macroglobulin superfamily of proteins, characterised by the presence of an internal thiol-ester bond, is seen in humans as α2-macroglobulin, pregnancy zone protein (PZP), and Complement components C3, C4 and C5. α2-Macroglobulin (α2m) is a multifunctional serum protein, whose primary function is serving as a protease inhibitor. Rather than a traditional active-site inhibition, α2m immobilises target proteases via proteolytic cleavage of its bait region resulting in structural reorganisation of α2m and molecular entrapment of the protease. The nature of the bait region sequence allows for cleavage by a wide number of proteases which thus become entrapped. Small amines such as methylamine can also induce α2m activation resulting in the same structural reorganisation seen in proteolytic activation. The crystal structure of Limulus α2m was not determined during this study, however this work represents the first reports of protein crystals of Limulus α2m activated with methylamine. Crystals were tested at the Diamond Light Source and diffraction was detected to 6Å with a predicted orthorhombic space group of P222 and unit cell dimensions of a = 115Å, b = 141Å, and c = 338Å. In addition to crystallographic analysis the Limulus Polyphemus α2m sequence was submitted to the I-TASSER server for structure prediction. I-TASSER predicted general structural homology with the human analogue although differences arise from the human model representing the activated form and I-TASSER building a native , non-activated structure for the Limulus homologue. The bioinfomatic analysis and structure prediction presented here provides convincing structural models coupled with novel insights into the activation mechanism of Limulus α2m and how this might relate to its functions downstream.