Abstract. 1. For the first time, long-term changes in total aerial insect biomass have been estimated for a wide area of Southern Britain.2. Various indices of biomass were created for standardised samples from four of the Rothamsted Insect Survey 12.2 m tall suction traps for the 30 years from 1973 to 2002.3. There was a significant decline in total biomass at Hereford but not at three other sites: Rothamsted, Starcross and Wye.4. For the Hereford samples, many insects were identified at least to order level, some to family or species level. These samples were then used to investigate the taxa involved in the decline in biomass at Hereford.5. The Hereford samples were dominated by large Diptera, particularly Dilophus febrilis, which showed a significant decline in abundance.6. Changes in agricultural practice that could have contributed to the observed declines are discussed, as are potential implications for farmland birds, with suggestions for further work to investigate both cause and effect.

Day and night sampling of windborne arthropods at a height of 200 m above ground was undertaken at Cardington, Bedfordshire, UK, during July 1999, 2000 and 2002, using a net supported by a tethered balloon. The results from this study are compared with those from the classic aerial sampling programmes carried out by Hardy, Freeman and colleagues over the UK and North Sea in the 1930s. In the present study, aerial netting was undertaken at night as well as daytime, and so the diel periodicity of migration could be investigated, and comparisons made with the results from Lewis and Taylor's extensive survey of flight periodicity near ground level. In some taxa with day-time emigration, quite large populations could continue in high-altitude flight after dark, perhaps to a previously underrated extent, and this would greatly increase their potential migratory range. Any trend towards increases in night temperatures, associated with global warming, would facilitate movements of this type in the UK. Observations on the windborne migration of a variety of species, particularly those of economic significance or of radar-detectable size, are briefly discussed.

The definitive version is available at www.blackwell-synergy.com Copyright Blackwell Publishing [Full text of this article is not avaialble in the UHRA]The within-field spatio-temporal distributions and relationships of two pest insects with stem-mining larvae, Psylliodes chrysocephala (L.) (Coleoptera: Chrysomelidae) and Ceutorhynchus pallidactylus (Marsham) (Coleoptera: Curculionidae), and their larval endoparasitoids, Tersilochus microgaster (Sz??pligeti) and Tersilochus obscurator Aubert (Hymenoptera: Ichneumonidae), respectively, were studied in a crop of winter oilseed rape [Brassica napus L. (Brassicaceae)]. The insects were sampled, at different life stages, at 40 spatially referenced points within the oilseed rape in 1998???99 and in the following crop of winter wheat. Distributions were analysed and compared using SADIE (Spatial Analysis by Distance IndicEs) and by tests of edge distribution. Tersilochus microgaster emerged from overwintering by the end of March and T. obscurator from mid April to mid May 2000. Tersilochus microgaster parasitized 10.8% of P. chrysocephala larvae, peak parasitism occurring in May. The distribution of each species was patchy and irregular. Psylliodes chrysocephala and its parasitoid were closely associated, but new generation C. pallidactylus and T. obscurator were less so, probably because of host mortality caused by the parasitoid. The two host???parasitoid pairs showed distributions that were polarized with respect to each other. The genesis of these spatial patterns is discussed in relation to the influence of wind direction, plant size, and interspecific interactions. The potential of these parasitoids as biocontrol agents in integrated pest management is discussed. Opportunities for conservation biocontrol in oilseed rape offered by spatio-temporal targeting of insecticides to avoid parasitoids and by reduced soil tillage are examined

Tersilochus obscurator Aubert and Tersilochus microgaster (Szépligeti) are larval endoparasitoids of economically-important stem-mining pests of winter oilseed rape (Brassica napus L.) in Europe. They are difficult to separate morphologically. Their hosts are Ceutorhynchus pallidactylus (Marsham) and Psylliodes chrysocephala Linnaeus, respectively. The parasitoids' taxonomic status, identification, host range and phenology were studied using genetic, morphometric and ecological data. The study used 527 female parasitoids from the UK and Germany, either field-collected in emergence traps or reared from field-collected host larvae. Two morphometric characters, the ovipositor sheath to first metasomal tergite ratio and the percentage of the mesopleuron spanned by the sternaulus, were measured. A 440 bp section of mitochondrial DNA cytochrome oxidase subunit I (COI) gene was sequenced from 35 parasitoids reared from C. pallidactylus, 20 reared from P. chrysocephala and individuals from two outgroups, Tersilochus heterocerus Thomson and Phradis interstitialis Thomson. Distinct and invariable COI sequences corresponded exclusively to each parasitoid group, confirming that T. obscurator and T. microgaster are discrete species. Measurements of host-reared and COI-sequenced specimens indicated that the ranges of both morphometric characters overlapped between species. Using these ranges as criteria, all but 3.6% of UK specimens and 2% of German specimens were identifiable to species without reference to host or phenology. There were differences in emergence phenology in the UK, adult T. microgaster emerging from winter diapause by 29 March 2000, T. obscurator emerging between 12 April and 24 May 2000. The value of molecular techniques in the identification of closely-related parasitoid species is discussed.