A detailed account is given of the structure of the mouthparts of Chloeon dipterum L. and Baetis rhodani Pictet, with a description of the mode of functioning based upon direct observations and the anatomical findings. Differences in the feeding apparatus are correlated with differences in the conditions under which the two species feed. The musculature of the mouthparts is compared with that of other genera of Ephemeroptera, and some of the changes that have been involved in the evolution of flattened forms such as Eodyonurus are suggested. Three kinds of variation in the food - 1. Seasonal, 2. Local, 3. Between lorvas of different sizes - were investigated by analysing the gut contents of samples of larvae taken at fortnightly intervals from three ponds and streams over a period of eighteen months. Existing techniques of food analysis are reviewed and a quantitative technique is described in which an estimation of the error in the results is possible. Descriptions of the habitais are given and the causes of variations in quantity and composition of the food ingested are discussed. The results are given of an investigation of the ability of C. dipterum and B. rhodani to ingest and digest algae in the laboratory. The presence of viable cells in the gut was detected by culturing the material on a medium suitable for algal growth.

The behaviour of the epidermal cell of the insect, Oncopeltus fasciatusy has been studied in the dorsal abdomen in three situations: during the moult cycle, wound healing and pattern regulation. This behaviour can be classified into seven categories: activation, division, movement, alteration in shape, death, differentiation and cuticle secretion. Data are presented on the first five categories. Aspects of cell behaviour studied during the intermoult period of the moult cycle consist mainly of activation and division. The exact stimuli for this behaviour have not been determined, although an increase in ecdysteroid titre may not be sufficient. The first mitotic figures in the moult cycle are concentrated behind the anterior border of the segment, but later the mitotic index is uniform over most of the segment. Cell behaviour induced after wounding consists largely of activation, division and movement. Degradation products from damaged epidermal cells are not solely responsible for this activation and the strongest influence appears to be the presence of an incision. Activated cells peripheral to wounds will not divide unless ecdysterone is present. Cells may divide beneath wounds and the condition required for this is probably the disruption of epidermal continuity for a minimum length of time. Cell behaviour after the confrontation of cells from different anteroposterior levels in the segment consists mainly of division and transverse elongation at the confrontation site. The intensity of this behaviour is explained by a difference in positional values between confronted cells so that there is a non-linear gradient of positional values along the segment with a discontinuity at the segment border. If this discontinuity is maintained by a special population of cells at the border, then the regeneration of segment borders can be explained by the formation of these special cells following the confrontation of cells with almost the maximum difference in positional values.

1) The Auchenorrhyncha of the Deeps, an area of calcareous grassland in Northamptonshire, were surveyed. Two contrasting sites within grassland, one with taller (50 - 70 cm) vegetation dominated by Brachypodium pinnatum and the other with shorter (10-20 cm) vegetation dominated by Festuca spp., were sampled with both an Univac vacuum sampler and a sweep net between April 22 and September 9, 1987. On two occasions sticky traps were also used. Most of the commoner species showed a marked preference for one or other of the sampling sites. The majority of the 40 species of Auchenorrhyncha recorded from the site during the entire study was found during the survey. 2) The nymphs of the commoner species of Cicadellidae encountered during the study were identified and described. Most of the identifications were made by rearing the nymphs to maturity by confining them in clip-cages on grasses, which were grown in plastic pots in a greenhouse. A key to the nymphs, illustrated by drawing and photographs, was constructed. 3) Choice experiments were conducted in a greenhouse on two of the common species of cicadellid recorded at the Deeps; Adarrus multinotatus and Turrutus socialis. Adult specimens of the two species were collected from the field and released into a cage with seven species of the commoner grasses found at the Deeps. Collections of the leafhoppers made from the grasses indicated that A. multinotatus was specific to Brachypodium pinnatum and Turrutus socialis had a wide host range, with a preference for Avenula pubescens and Festuca rubra. 4) Choice experiments were conducted in the field over a three year period (1990 -1992). Replicated grass species, grown in plastic pots, were sunk into the ground in both the sites initially surveyed at the Deeps. Auchenorrhyncha were collected from the grasses at intervals by carefully removing pots from the ground and brushing the plant inside a muslin cage. Auchenorrhyncha removed from the grasses in this way were collected from the cage with pooters. The data obtained from this aspect of the study indicated that a number of species of Auchenorrhyncha were specific to one grass species or genus, a few species were associated with a well defined range of grasses and a third group (the largest) had a wide host range. 5) During the first year of the field choice experiments an investigation into the role of plant nitrogen in host selection by Auchenorrhyncha was undertaken. The response of Auchenorrhyncha to the 'natural' range of total leaf nitrogen found in unfertilised grasses grown in pots and their response to grasses fertilised with NH4NO3 were studied. Total leaf nitrogen was measured using a micro-Kjeldahl digestion. Although this aspect of the study was limited, the results indicated that only a few species at the Deeps selected plant hosts with a high nitrogen content. 6) Greenhouse no-choice experiments were conducted on the survival and oviposition of Adarrus multinotatus and Turrutus socialis and the survival of Criomorphus albomarginatus on a range of potential host grasses. The survival and oviposition of specimens contained in clip-cages on potential host grasses grown in plastic pots was monitored. The results obtained supported the results of the choice experiments, indicating that A. multinotatus was specific to B. pinnatum, T. socialis had a wide host range, and C. albomarginatus was specific to F. rubra. 7) Observations were made on the oviposition behaviour of a number of species, in addition to those described in 6) above, which were confined on host plants in clip-cages. Dead or living leaf sheaths were most commonly used for oviposition, although flower stems and leaves were also used. Generally, the species observed appeared to be specific in their choice of oviposition site.

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Life on Earth has evolved under regular cycles of light and dark. Only in the past two centuries have humans begun altering habitats with electric lighting. The use of artificial light at night (ALAN) is growing annually and broad-spectrum 'white' _ lighting is taking centre stage. Many new-technology 'white' lights are described as 'environmentally friendly' or 'green' due to their reduced energy use relative to traditional technologies. While use of low-energy lighting may help reduce overall carbon emissions and therefore the severity of climate change, little is known about their impact on animal behaviour and ecology. Determining the ecological effects of light pollution has high policy relevance in the UK as it is a potential driver of recent insect declines. Understanding how ALAN affects insects will be key for effective conservation biology. I used experimental approaches to investigate the impact of new technology lighting, specifically 'white' light-emitting diodes (LEOs), on insect behaviour and ecology. LEOs attracted fewer insects and a smaller diversity of insect families than competing 'white' metal halide street lights. LEOs did not attract a greater abundance or diversity of insects than traditional narrow-spectrum high-pressure sodium street lights. Slight alterations to the spectral distribution of domestic LED light bulbs ('cool-white' and 'warm-white') did not result in any significant difference . . in insect .. attraction. Overall LEOs attracted significantly fewer insects than competing (fluorescent) lights which emitted ultraviolet light. I found that moths are less likely to respond to predatory bat calls in the presence of LED lighting, suggesting that white light can have nuance effects on insect behaviour affecting speGies in unforeseen ways. I suggest ways to mitigate for the impacts of ALAN on insects and I recommend legislative action to prevent overuse of lighting. An improved understanding of how insects respond to new white lighting will have far reaching benefits via their roles as pollinators, vectors of disease, nutrient recyclers, decomposers, predators and prey items.

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