STUDIES OF THE BIOLOGY OF THE DEATH‐WATCH BEETLE, XESTOBIUM RUFOVILLOSUM DE G.

Abstract

Summary 1 This paper, the second in a short series on biological studies of the death-watch beetle, Xestobium rufovillosum De G., is concerned with the life of the adult, egg-laying and hatching. 2 Times of pupation and emergence in the natural habitat of the insect in decayed parts of willow, and in timbers in buildings are discussed and compared. 3 The rate of development of the reproductive organs after pupation and until egg-laying starts, is described. 4 The habits of the adults, activity, tapping, fight and mode of pairing are commented upon. 5 The major part of the paper deals with oviposition which has been studied out of doors and under controlled tempemture and humidity in the laboratory. 6 Out of doors forty to eighty eggs per female are laid during May and June over a period of 6–9 weeks. The egg stage lasts from 3 to 5 weeks, according to temperature conditions. 7 In the laboratory, oviposition and the hatching of the egg were studied at 15, 20, 25 and 30°C. and relative humidities of 23, 41, 53, 75, 86 and 95 %. The results are discussed in relation to the effect of temperature, relative humidity and saturation deficiency. 8 “Indices of suitability” for various combinations of temperature and humidity in relation to egg-laying and hatching are calculated from the experimental data. 9 It is shown that an increase in temperature to a maximum between 25 and 30°C. is favourable but that the optimum conditions must include a low saturation deficiency. The data demonstrate an increasing tolerance, by the insect, of dryness associated with a rise in temperature. 10 The application of these findings to the occurrence and spread of Xestobium in buildings is briefly discussed.