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The Desert locust Schistocerca gregaria is a major world pest that causes substantial agricultural and economic damage. Effective pest control relies on effective monitoring, which requires knowledge of locust microhabitat selection. Yet little is known about microhabitat selection of solitarious adult locusts in the field. We conducted field surveys to investigate fine-scale diel temporal and spatial distributions of solitarious adults in the Sahara Desert in Mauritania, a major breeding and recession area. We found that solitarious adults moved among different, specific microhabitats throughout the 24-h period in a cyclical manner. At night, they roosted in trees, moved to the ground to feed shortly after dawn, sheltered in low vegetation during the hot midday, and returned to the ground in the late afternoon. Hence, they switched microhabitats and plant species throughout each day. These cyclical daily movements among diverse microhabitats and specific plant species were correlated with time of day, light intensity, temperature, humidity, and specific plant species, and may relate to anti-predator defence, thermoregulation, and feeding. The present study suggests that locust monitoring should be adjusted, based on time of day, locust age, phase state and relative abundance of specific plant species. For example, we recommend surveying ground after morning and trees at night, for solitarious adults, when at low density.

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SUMMARYPlants are the nature's biochemical factories. They bio-synthesize a diverse array of different natural products, such as alkaloids, terpenes and terpenoids, phenolic compounds, flavonoids and coumarins through their structural mechanisms to reduce insect attacks, both constitutive and inducible, while insects have evolved strategies to overcome these plant defenses.There is a widespread effort to find new pesticides, and currently it is focused on natural compounds such as flavonoids, coumarins, terpenoids, and phenolics from diverse botanical families from arid and semi-arid lands. Algeria by the diversity of its habitats has a very diverse flora. Some of these plants have very interesting insecticidal properties. The aim of this study is to evaluate the insecticidal effect of the plant Artemisia judaica L. (Asteraceae). The crude ethanol extract of the plant A. judaica was tested on the black bean aphid Aphis fabae Scop. Four doses (12.5, 6.25, 3.12 and 1.56 mg mL -1 ) were tested on contact wingless adults. The results have showed that the tested extract has been very powerful to aphids. At the highest dose 12.5 mgmL -1 , the 100% of mortality were recorded 2 hours after treatment, and for the lowest dose (1.56 mgmL -1 ) it was after 96 hours. The LD50 calculated 2 hours after treatment from the regression lines Probit = ƒ (doses) shows that it is 2.75 mgmL -1 . This powerful insecticidal activity of the tested crude extract could be due to the richness of the plant on phenolics compounds known for their bio-insecticide action.

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