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Abstract. 1. The phagostimulatory activity of a range of sugars, amino acids, vitamins, salts, phospholipids and sterols to Locusta migratoria (L.) was assessed singly and in combinations. 2. The hexose and disaccharide sugars were shown to be highly stimulatory. 3. Of the amino acids only l‐proline and l‐serine elicited feeding responses and none of the salts, vitamins, phospholipids or sterols was stimulatory when presented singly.

1. The diurnal periodicity of flight of delphacids and cicadellids associated with rice was assessed by suction trapping.2. All the delphacids examined and most cicadellids showed a bimodal, crepuscular pattern of flight, the major peak occurring in the evening.3. Some cicadellids showed a unimodal crepuscular pattern of flight activity with the peak occurring in the evening, whereas flight activity of Cofana spectra and Cunimaculata continued throughout the night. Changes in the periodicity of flight activity of Nilaparvata lugens, Sogatella jkrcqera, Recilia dorsalis and Macrosteles stnvrons were observed in relation tophases of the moon and the nature of the habitat. 5. Periodicity of take-off for N.lugens, Sfircifera and R-dorsalis assessed by canopy net traps also showed a bimodal, crepuscular pattern with the major peak occurring in the evening. 6. The significance of diurnal periodicity is discussed in relation to the flight behaviour of the insects studied.

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The feeding behaviour of Nilaparavata lugens was monitored on three rice varieties showing different levels of resistance in the Philippines, using a video‐assisted observation method. N. lugens made more frequent, shorter probes on the moderately resistant IR46 and resistant IR62 rice varieties than on the susceptible IR22. Honeydew production was significantly lower on the resistant varieties though insect weight gains in 24 h were similar on IR46 and IR22, both being significantly greater than on the highly resistant variety. Population development, growth index and damage ratings were low on IR62 indicating antibiosis and/or non preference. When IR46 plants were infested as seedlings population increase, growth index and damage ratings were similar to those on the susceptible IR22. When infested at a later stage of plant growth the damage rating showed a moderate level of resistance though some population development was maintained, indicating antibiosis and tolerance. N. lugens started probing less frequently after surface exploration on both resistant varieties than on IR22 suggesting the presence of a resistance factor associated with the surface waxes of these varieties. RÉSUMÉ Comparaison des comportements alimentaires de Nilaparvata lugens sur variétés de riz résistantes ou sensibles Le comportement alimentaire de Nilaparvata lugens sur variétés de riz, sensible (IR22), partiellement résistante (IR46) et fortement résistante (IR62), a été contrôlé avec une méthode associant la vidéo à l'observation. N. lugens faisait des piqûres plus fréquentes et plus brèves sur IR46 et IR62, que sur la variété sensible. La production de miellat était significativement plus faible sur les variétés résistantes, bien que les gains de poids des insectes aient été les mêmes en 24 h sur IR46 et IR22, les deux étant significativement supérieurs à celui sur IR62. La croissance de la population, l'indice de croissance et le taux de dégâts étaient tous plus faibles sur IR62, ce qui révèle une antibiose et/ou une absence de préférence. Quand la contamination des IR46 a au lieu au stade semis, la croissance de population, l'indice de croissance et le taux de dégâts étaient semblables à ceux de la variété sensible IR22. Quand la contamination avait lieu à un stade ultérieur, le laux de dégâts révélait un niveau modéré de résistance bien qu'une certaine croissance de population se soit maintenue, ce qui révèle antibiose et tolérance. Après exploration de la surface des feuilles des deux variétés résistantes, N. lugens sondait moins fréquemment que sur IR22, ce qui laisse présumer un facteur de résistance associé aux cires superficielles de ces variétés.