Role of certain environmental factors in determining the efficiency of host plant selection by an insect
1978
SAXENA, K.N.
The present observations on Dysdercus koenigii together with the available literature provide a basis for considering how host plant selection by an insect is controlled not only by the plants but also by the environment around them. Sensory stimuli which affect the host selection behaviour of an insect emanate from plants and also from the general environment. The plant stimuli include those perceived at a distance which are directional and those perceived by contact. A humidity gradient provides a non-plant-specific directional stimulus in the host selection behaviour of Dysdercus, whereas temperatures and the overall humidity act non-directionally. Environmental factors influence metabolic processes of an insect and, thereby, its physiological state which, in turn, modifies its behavioural responses to the same stimuli. In this work the host selection behaviour of Dysdercus was influenced by its previous exposure to different temperatures and humidities which in turn influence physiological changes associated with age-cum-starvation and desiccation. The insect's arrival on and initial selection of a plant depend on its kinesis and taxis. When outside the effective zone of directional stimuli, the insect shows variable levels of kinesis. The latter is determined mainly by the non-directional background stimuli as well as the insect's physiological stage. When the kinetic activity of the insect brings it within the zone of perception of the directional stimuli from a plant, the taxis may be positive or negative. Increased kinesis increases the chances of reaching the zone of taxis.
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