Thermal Biology of the Predatory BugsOrius thripoborusandO. naivashae(Hemiptera: Anthocoridae)

Abstract

Developmental and reproductive traits of two little studied anthocorid predators from southern Africa, Orius thripoborus (Hesse) and Orius naivashae (Poppius), were examined at several constant temperatures. Development was studied at 12, 15, 23, 25, 29, 33, and 35°C. Eggs of both species did not hatch at 12°C. Nymphal survival was poor at 15°C for O. naivashae, and at 33°C and 35°C for O. thripoborus. Total development time of males and females decreased with increasing temperature. Based on a linear degree-day (DD) model, lower threshold temperatures for egg and nymphal development were estimated to be 9.4 and 10.2°C for O. thripoborus, and 11.3 and 11.8°C for O. naivashae. Thermal requirements for these stages were 73.8 and 191.1 DD, and 65.2 and 168.2 DD, respectively. Adult reproduction was studied at 15, 19, 25, and 33°C. Highest lifetime fecundities for O. thripoborus and O. naivashae were found at 25°C. At 15°C, half of the O. thripoborus females oviposited, whereas O. naivashae females only produced infertile eggs. At 33°C, however, most of the O. naivashae females produced eggs, whereas O. thripoborus females did not oviposit. Our observations suggest that O. thripoborus is adapted to a slightly cooler temperature range as compared with O. naivashae. The complementarity of both predators in terms of their temperature adaptation opens possibilities for their use in biological control programs at different times of the season.