Most quantitative ecological research on aquatic insects has addressed their immature stages. To understand their population dynamics, however, information on the adult stage is essential. This study aimed to obtain quantitative estimates of life cycle features, such as emergence, adult life span and fecundity, and to develop further the methods used. Field studies on adult insects revealed patterns in spatial and temporal distribution and the effect of land use on lateral dispersal. Finally, methods used to estimate dispersal and gene flow were discussed. Studies on Leuctra nigra demonstrated that their emergence is associated with the quantity of emergent substratum locally available. Female L. nigra can be classified as "immature" and "mature", based on the maturity of their eggs, and this was used as an approximate age marker in studies of adult survival and spatial distribution, and to improve estimates of emergence by excluding mature females from catches in pyramidal traps. A female biased sex ratio observed in L. nigra stemmed from a discrepancy in the life span of the genders, with shorter-lived males, combined with a change in habitat by the females. Most adult aquatic insects stayed close to the stream. Thus, half of the stoneflies travelled less than 18 m lateral to the channel and the dispersal ranges of caddis flies and female of mayflies were even shorter. Comparison of the movement along the stream with the lateral dispersal suggests that most dispersal is in the 'stream corridor' itself. Little distinction was found between lateral dispersal in different catchment land uses. It is still too early, however, to conclude that dispersal is unaffected by land use. Temporal and spatial distribution of leuctrid stoneflies differed among neighbouring catchments, with Leuctra inermis and L. nigra dominating in moorland and catchments managed for forestry, respectively. Both physiochemical factors and biological interactions could explain this distribution.

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<i>Zygaena</i> species are aposematic and have toxic properties in all stages of their life history. Their contrasting coloration that is primarily red and black or yellow and black is of great ecological significance because it is considered to be a means of defence against potential predators, such as birds, insectivorous mammals and reptiles. The adults form part of a Müllerian mimicry ring involving each other, red and black or yellow and black meloid beetles, bugs and other insects. One species, <i>Z. ephialtes, </i>has a special ephialtoid morph that mimics species of the genus <i>Syntomis</i> and its involvement with them is considered to form a special Müllerian mimicry ring that behaves in a Batesian manner. That is to say, the degree of distastefulness and the genetics of mimicry, colour and pattern polymorphism in <i>Z. ephialtes</i> indicate that it takes an intermediate place between classical Batesian and Müllerian mimicry. The larvae of one or of different species can exhibit aposematism and/or procrypsis, i.e. the early instars of the larva can be cryptic and only the last instar is aposematic, or in a given region the larvae of a species are aposematic in all their instars yet in another region they are cryptic. Moreover, from a distance the adults might be mistaken for leguminous seedpods and the flower heads of sedges when they are at rest on herbage and their aposematic coloration comes into play only when a potential predator approaches them closely. Under certain circumstances, larvae that are aposematic can also be cryptic because their disruptive coloration allows them to blend into the background of light and shade when they are at rest or feeding on their host-plants.

No description available.

No description available.

The potential of different field boundary types in lowland farmland to contribute to arthropod biodiversity and sustainable agriculture was investigated. Field boundaries, categorised according to nationally applicable definitions, were found to represent ecologically differing habitats based on their woody abundance and the frequency of young and mature emergent trees. These habitat characteristics were determining factors in the community structure and composition of overwintering epigeal arthropods. Hedgerows supported the most species rich carabid and staphylinid assemblage. Degraded hedgerow boundaries supported the most equitable carabid community, and provided a refuge for carabid species with poor dispersal power to a greater extent that hedgerows or post and wire fences. The grassy and natural regeneration vegetation associated with post and wire boundaries supported high densities of all taxa particularly overwintering carabid and staphylinid polyphagous predators. A subset of all field boundary types was required for complete species representation, indicating that maximising the heterogeneity of field boundary habitats represented at the farm-scale will enhance arthropod biodiversity in farmland. Carabidae and Staphylinidae actively selected overwintering sites and the physiological condition of polyphagous predators was generally high. It was concluded that heterogeneous distributions in field boundaries were more likely to be the result of differential microhabitat selection rather than differential survival overwinter. This indicated that favourable overwintering microhabitats occurred in all field boundary types. Generally, overwintering survival did not appear to be a regulating factor in the population dynamics of polyphagous predators. Margins adjacent to pre-existing boundaries may contribute to enhanced densities and physiological condition of some polyphagous predators, both over winter and in early spring. The results were discussed in relation to field boundary management and agri-environment policy.

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The effects of aldicarb and its two major toxic breakdown products, aldicarb sulphoxide and sulphone have been investigated using several species of nematode. Of the three compounds, aldicarb was the most effective, reducing nematode hatch in water and soils, their dispersal on treated agar and locomotory activity. Meloidogyne incognita larvae accumulated in treated pot soils and their invasion of host plant roots was delayed. In soils the contact of nematodes with a paralysing dose of the non-volatile nematicide or its sulphoxide is of fundamental importance in nematode control. In tomato roots the reduction of meloidogyne invasion can only be attributed to the persistence of minor amounts of the sulphone derivative. Control of invasion by the retention of toxic residues in roots is less effective since aldicarb and its breakdown products accumulate in the foliage. The movement patterns of second stage Meloidogyne and Heterodera larvae altered in the presence of these carbamoyloximes from open to closed spiralling, the tracks becoming increasingly tortious with exposure. Contracted paralysis of nematodes resulted, especially with aldicarb and its sulphoxide, the nematodes becoming almost motionless. When the nematicide treatments were discontinued, nematodes regained their activity. Recovery was generally more rapid after sulphoxide or sulphone treatment. Of the three compounds, aldicarb had the greatest affect on stylet movement, stimulating abnormal protraction except in Xiphinema. Maximum stylet protraction corresponded with maximum body inactivity. The permeation of two nematode species by C - labelled aldicarb was investigated. These were permeable to aldicarb which accumulated within them. An equilibrium was reached between the nernaticide inside the nematode and that in the exposure solution. After penetreation the parent compound was rapidly converted to its sulphoxide and subsequently to the corresponding oxime and nitrile. The egress of labelled sulphoxide from treated Panagrellus was slow. The results obtained in these investigations are compared with relevant published data.

No description available.

No description available.