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Using the foraging movements of an insectivorous bat, Myotis mystacinus, we describe temporal switching of foraging behaviour in response to resource availability. These observations conform to predictions of optimized search under the Lévy flight paradigm. However, we suggest that this occurs as a result of a preference behaviour and knowledge of resource distribution. Preferential behaviour and knowledge of a familiar area generate distinct movement patterns as resource availability changes on short temporal scales. The behavioural response of predators to changes in prey fields can elicit different functional responses, which are considered to be central in the development of stable predator -prey communities. Recognizing how the foraging movements of an animal relate to environmental conditions also elucidates the evolution of optimized search and the prevalence of discrete strategies in natural systems. Applying techniques that use changes in the frequency distribution of movements facilitates exploration of the processes that underpin behavioural changes.

Dialkylaminovinylquinones can often be synthesised in good yield from halogenated quinones, acetaldehyde, and secondary amines, isolation of the enamines being unnecessary. A dialkylaminobutadienyl-quinone has been prepared in the naphthalene series, by using 1-diethylaminobutadiene or, less efficiently, a mixture of diethylamine and crotonaldehyde. Replacement of chlorine in the blue dialkylaminovinyltrichlorobenzoquinones can lead to purple or green compounds. For comparison, some reactions between quinones and primary and secondary amines have been carried out. The light absorption properties of these coloured compounds are discussed; it is considered that the side-chains, (CH=CH),*NR,, in the new quinones are of truuts-geometry.

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