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University of Khartoum (2003)

Reproductive Behaviour Of The Solitarious Desert Locust, Schistocerca Gregaria (Forskål), In Relation To Semiochemical Attributes Of Desert Plants

Ely, Sidi Ould

Titre : Reproductive Behaviour of The Solitarious Desert Locust, Schistocerca Gregaria (Forskål), in Relation to Semiochemical Attributes of Desert Plants

Auteur : Ely, Sidi Ould

Université de soutenance : University of Khartoum

Grade : Master of Science (MS) 2003

Résumé partiel
Sexual attraction in the desert locust, Schistocerca gregaria (Forskål), was investigated by monitoring sexual behaviour of solitary-reared, gregarizing and gregarious locusts. Gregarizing males were significantly more attracted to volatiles from solitarious females than the solitarious males, depending on the length time they had been crowded. 24-day-crowded-solitarious males, traversed the longest distance toward the source of stimuli and also showed additional behavioural activities compared to the control, when no solitarious female was kept upwind. Besides, solitarious females despite grouped together did not gregarize and behaved similarly to solitary-reared ones. However, when solitarious females were grouped together from fledging for 24 days in a lower chamber of a bi-chamber cage with soltarious males (kept in the upper chamber) with olfactory and visual contact (but no tactile contact), they showed significantly more attraction to solitary-reared males. Visual stimulus when provided in addition to olfactory stimulus, have been revealed important role in sexual attraction, as is involving both test and target insects in the sexual behaviour scenario and therefore, the number of test insects reaching the signal source increased significantly when compared to olfaction alone. On the other hand, diel behavioural activity patterns of adult solitarious desert locust that were collected from the field in Port Sudan were investigated by monitoring walking/running, resting, taking off, and scanning in a wind tunnel. Solitarious locusts that had been propagated in the laboratory for 20 generations were also observed for comparison. In both groups of locusts, insects were significantly more active after sunset and this activity attained peak level at 1-2 hours after dusk. Of the two groups, solitarious locusts collected from the field were significantly more active. In the nocturnal phase, the former traversed distances that were about seven times those covered by laboratory-reared insects. Overall, the results showed that the repertoire of behavioural activities of solitarious locusts is maintained in laboratory-reared insects, albeit at a lower level. The implications of these observations in the behavioural ecology of the desert locust were discussed. In the field, (Red sea coast) solitarious locusts feed on a range of desert plants (Heliotropium spp., Tribulus spp., Schouwia spp., …) whilst in the laboratory, locusts colonies were reared on wheat seedlings and wheat bran


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