Temperature influences walking speed and walking activity of Trichogramma brassicae (Hym., Trichogrammatidae)

Walking speeds and walking activities (walking time divided by total time) of Trichogramma brassicae were determined at 12, 16, 20 and 25 degreesC. Wa lking speed was measured during a 5-min period, and walking activity over a 4-day period. Both walking speed and walking activity were strongly influe nced by temperature. Walking speed increased linearly with the temperature and was twice as high at 20 as at 12 degreesC. At 25 degreesC, walking acti vity was high during the whole day, at 20 and 16 degreesC it decreased duri ng the afternoon, whereas at 12 degreesC the wasps became most active only at noon or later. At low temperatures, there was a strong individual variat ion in walking activity. At 25 degreesC, T. brassicae was active most of th e time, so the area searched per time unit can only increase at temperature s above 25 degreesC if walking speed increases. At temperatures below 20 de greesC, searching was more restricted by low walking activity than by low w alking speed. Even disregarding other effects of temperature, the reduction in walking speed and walking activity at suboptimal temperatures means tha t T. brassicae can only search half of the area at 20 degreesC. and only on e-seventh at 15 degreesC that it can search at 25 degreesC.