No abstract

SummaryField scale experiments carried out over three years showed that chlorpyrifos reduced the numbers of several carabid beetle species caught in pitfall traps. Fonofos seed treatment was also shown to affect selected species. Consideration of the biology of individuals of groups of species provided explanations of why some species such as Nebria brevicollis, Notiophilus spp., Bembidion spp., and Trechus quadristriatus were severely affected by one or other of the chemicals, whereas other species (e.g. Amara spp., Harpalus spp.) were able to survive or recolonise pastures shortly after chemical application. Measurements of elytral and pronotal widths and counts of mature eggs in N. brevicollis, which was trapped in reduced numbers over a long period, were made and provided some information about the mode of action of these chemicals.

SUMMARYA novel quantitative method (defined‐area trapping) devised in New Zealand for sampling slugs was tested in pastures in the UK and compared with cold water extraction processes and surface searching. Despite the different soils and conditions compared with New Zealand, the technique gave results for the UK comparable with accepted methods of estimating slug density with savings in time and labour and provided a non‐destructive means of sampling for slugs.

In commercial farming practice herbicides may be used to eradicate or manipulate the flora in the base of hedgerows. The effect of this on the carabid and spider communities was assessed. The carabid and spider communities of a hawthorn hedge alongside a semipermanent sward and of the adjacent part of the field were sampled using pitfall traps. The hedge was divided into three replicates of two herbicide treatments (‘Broadshot’ and ‘Roundup’) and a control. The carabid data were ordinated (DECORANA) and showed that both herbicide treatments affected the communities; the spider data showed similar but less marked responses. Both herbicides had important effects on the carabid communities, but, the spider communities were most affected when only the broadleaved forbs were removed. Zusammenfassung Über die Auswirkungen einer chemischen Entfernung der Heckenboden‐Flora auf die Gemeinschaftsstruktur der den Feld‐ und Heckenboden bewohnenden Laufkäfer (Col., Carabidae) und Spinnen (Araneae) In der kommerziellen landwirtschaftlichen Praxis werden Herbizide verwendet, um die Pflanzen am Boden von Hecken zu entfernen oder zu manipulieren. Die Carabiden‐ und Spinnengemeinschaften einer Weißdornhecke entlang einer semipermanenten Grasnarbe sowie des angrenzenden Feldteils wurden mit Hilfe von Bodenfallen gesammelt. Die Hecke wurde in 3 Parzellen gegliedert, von denen 2 mit Herbiziden (“Broadshot” und “Roundup”) behandelt wurden, während die 3. Parzelle als Kontrolle unbehandelt blieb. Die Carabidenfauna wurde einer DECORANA‐Datenanalyse unterzogen. Aus den Ergebnissen geht hervor, daß beide Herbizide die Gemeinschaft der Laufkäferarten wesentlich beeinflußte. Die Spinnen reagierten im allgemeinen weniger stark. Sie zeigten ihre größten Veränderungen, wenn die breitblätterigen Pflanzen entfernt wurden.