Role of temperature in habitat selection and activity patterns in the ground beetle Angoleus nitidus

Habitat selection and adjustment of diurnal activity rhythm are two strategies that ectothermal organisms use in order to avoid unfavourable environmental conditions. Nevertheless, these patterns are variable in time, and differences in physiological requirements or weather changes can produce different responses in the population. In this paper we studied in the field during the breeding period of Angoleus nitidus Dejean 1828 (Coleoptera: Caraboidea: Pterostichidae): a) the habitat selection patterns of males and females and b) the diurnal activity pattern of both sexes under different temperature conditions, taking account of the different sexual physiological constraints during this period. Habitat selection by both sexes was quite similar, although females selected more strongly the habitat where the vegetation was the tallest. This result was interpreted as a search for suitable oviposition sites by females. On fine days, when the temperature at midday was a limiting factor for the activity of beetles, bimodal activity patterns were found, although male and female behaviour was marginally different. On cloudy days the curves obtained were unimodal being also different between sexes. Females were more cautious than males even when temperature was not restrictive. These results were interpreted as a reflection of the different temperature tolerance existing between males and females due to physiological differences inherent in the breeding period.