The effect of constant temperature and humidity on the development, longevity and productivity of Ahasverus advena (Waltl.) (Coleoptera: Silvanidae)

Abstract

The development and productivity of Ahasverus advena (Waltl.) was studied on kibbled wheat at humidities ranging from 65 to 90% r.h., in combination with temperatures varying from 15 to 35 °C. Longevity was also investigated between 10 and 25 °C. At 70% r.h. complete development took 67, 58 and 48 days at 20, 22.5 and 25 °C, respectively, while cumulative mortality was 94, 52 and 65%. At 90% r.h. complete development took 70, 46, 31, 26, 21, 16 and 22 days at 17.5, 20, 22.5, 25, 27.5, 30 and 32.5 °C, while cumulative mortality was 94, 68, 63, 44, 58, 45 and 57%. At 65% r.h. longevity increased from 18 days at 10 °C to 63 days at 15 °C and then decreased to 35 days at 25 °C. At 90% r.h. the mean longevity increased from 69 days at 10 °C to 267 days at 15 °C and then declined to 99 days at 25 °C. A. advena was not productive at any humidity at 15 °C, nor at 65% r.h. at temperatures below 25 °C. Productivity also failed at 70% r.h., at temperatures below 20 °C. However, at 80 and 90% r.h. productivity was markedly high at 17.5, 20 and 25 °C and 50 adults produced a mean of 235 progeny in 3 weeks at 90% r.h., 25 °C. Although the species cannot develop under the cool, dry conditions of temperate storage, adults can survive for long periods under these conditions. On farms it may develop in manure heaps and mouldy straw bales and fly to grain stores when the weather is warm.