4 RESULTS

THE RESULTS of the experimental trials for Stegobium paniceum and its various developmental stages are given in table 1. In general, mortality increased with exposure time. Eggs and pupae appeared to be the most resistant developmental stage, though complete mortality was observed for all developmental stages after 2-hour exposure to −20�C.

TABLE 1 Average Percent Mortality(s) of the Various Development Stages of Stegobium paniceum Following Exposure to −20�C for Varying Periods of Time

No attempt was made to determine mortality at temperatures other than −20�C, given that this temperature can be readily achieved using domestic freezers and therefore has immediate application. Indeed, it is precisely for this reason that this temperature is commonly used in museum practice.

Though only a brief exposure to −20�C is necessary to achieve high mortality rates for unprotected Stegobium paniceum, under practical working conditions insects may well be insulated against the cold, and thus much longer exposure periods may be required. Under these circumstances various forms of freeze-resistance such as cold acclimation may occur, in which case it would be difficult to establish the appropriate exposure period without first determining the effects of low-temperature acclimation on the developmental stages of Stegobium paniceum. In the absence of such information the rate of cooling should be maximized, as recommended by Florian (1986).