Knockdown in insects following application of an insecticide may be defined as the state of intoxication and partial paralysis which usually precedes death. Pyrethroid insecticides cause knockdown within a few minutes in contrast to the slower action of other groups of compounds. Users throughout the world have varying interpretations of knockdown and may apply different emphasis depending upon the species involved and local application techniques. To obtain valid assessments it is necessary to carry out tests under the most realistic conditions possible and to see that the effects of variations in procedure are taken into full account. Some factors which influence knockdown are: single rapid dosing or continuous pick-up during the observation period ; size and distribution of spray droplets; size of test chamber; interaction in mixtures of synergist and insecticides; use of organic solvents or water-based formulations. Examples of these are given.

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This article engages in debates about the potential for aesthetics to be a positive, ethical, and moral frame for relating to the environment. Human-environment relations are increasingly tied up with aesthetics. We problematize this trend by contending that aesthetics is an insufficient paradigm to motivate and shape environmentalism because it exceptionalizes some landscapes while devaluing others. This article uses four illustrative case studies to complicate aesthetic environmentalist frames. These case studies indicate that even when positive aesthetic qualities are deployed in environmentalist advocacy, their usefulness is mitigated by a range of factors including: sensationalization, obfuscation, and further degradation.

The development of a mathematical model which, by quantifying the interaction of a population of houseflies with an ageing spray cloud, is capable of predicting the knockdown and kill performance of insecticidal aerosol formulations shown against houseflies, Musca domestica L., will be presented in a series of four separate papers. In this first paper, measurements were made of insecticide collected by houseflies during free flight using a standard room‐spray technique. With pressure‐packed aerosol formulations where the solvent is the principal change, it was shown that both knockdown and mortality responses of the insects were directly related to dose collected. The process of droplet collection was most significantly influenced by their size and availability, dependent upon the time after spraying, the position of insect release and the activity of individual adult M. domestica. The knockdown or mortality response of the insect to given amounts of insecticide was largely unaffected by the remaining solvent, although, with mineral oil, some inhibition was noted at low mortality levels. The amount of insecticide accumulated by houseflies in their initial flight was of prime importance in determining the overall effect. Flies remaining not knocked down at the end of the exposure period were shown to be so because they had accumulated less toxicant and not necessarily because they were more tolerant of the insecticide. The establishment of a relationship between the number of flies in flight and time after release has provided a key function for incorporation into the model.

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