摘要：

Early records of secondary rhinaria on the antennae of winged sexualis-dd [Sx-dd] , and of membranous scent plaques on the thickened tibiae of the pedes-III [P-I ll-Ti] of the sexualis-c;>c;> [Sx-c;>c;>] , suggests that there exists a pheromonal communication system in the sexual generation of aphids . Analysis and comparison of the results of further morphological studies and physiological experiments show, however, that this alone does not provide a distinctive mark of Sx-c;>c;>, and that it does not work as a long-distance attractant. The primary host tree species of a heteroecious aphid species not only acts as a species-specific oviposition site , but also as the specific rendevous and mating place. Winged gynoparae and Sx-dd, starting from secondary hosts, only reach and settle on the primary one after a non-directional long-distance flight guided by an optical two-pigment receptor-system, and after its short-distance discrimination by trial and error with the help of olfactorial, gustatorial and tactile probing. When running and searching non directionally on leaf or twig surfaces of the host , a Sx-d will casually contact and enter the scent range of a pheromon producing Sx-c;> waiting for copulation . Within such range , the radius of which varies species-specifically > 2 / < 1 0 cm but being modified by slow air currents, the female pheromon acts as arrestant , attractant and aphrodisiacum: The Sx-O is induced to stay within the scent range , is led further on to the Sx-c;> along a concentration gradient, and will become sexually more excited . As the pheromon is not species-specific , the olfactorial response to it can be superimposed by further optical orientation. Visual stimuli such as form and colour of a possible mating partner seem to be species-group-specific , they inhibit a further direct reaction to the odour source but are still enhanced by the latter. In some species, a rhythmical up and down movement of the abdomen and more conspicuously of the P-III can be observed . This is suggested to be (a) a mean of better pheromon spreading, (b) a specific visual signal , and (c) perhaps a mean of courtship pattern and source for sound production. The possible occurrence also of an acoustic communication system in sexuals , confirmed for virgin generations of other species , needs further attention . Sexual partner finding in aphids is based on a complex orientation process in which long distance optical as well as short-distance olfactorial , optical and tactile female stimuli and male responses are envolved . Due to this complexity , simple methods of attraction and trapping of sexualis-dd, as successfully practised with the biological control of other pest insect groups, are not applicable to aphids .

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