Attraction of Spodoptera littoralis Larvae to Colours

Abstract

DURING a research programme on phagostimulants^1–3 for the larva of the Egyptian cotton leafworm, Spodoptera littoralis Boisd., it was found that their incorporation into poison baits did not sufficiently improve the latter's attractivity. Further stimuli, for example optical ones, seemed to be needed. We therefore determined the influence of edible colours, similar to those used in studying boll weevil attraction⁴, on the feeding rate of S. littoralis. A range of commercial food colours of the ‘Edicol Supra’ and ‘Edilake’ ranges (Imperial Chemical Industries, England), now produced under the label of ‘Certicols’ and ‘Certolakes’, respectively (Williams (Hounslow) Ltd), were tested. The ‘Edilake (Certolake)’ colours are aluminium lakes containing a high proportion of alumina as extender of the corresponding ‘Edicol Supra (Certicol)’ dyes, which are sodium salts. ‘Edilakes’ are used mainly when water-soluble food colours would be unsuitable, for example in fatty or oily media, and contain generally from 15 to 25% of the corresponding ‘Edicols’.