1 INTRODUCTION

CONCERN FOR the safety of museum personnel when using chemical fumigants for the treatment of insect-infested museum objects has in recent years led to a greater emphasis on the development of nonchemical methods of pest control. One alternative that has been considered is freezing. Indeed, freezing has been employed for a number of years in libraries, herbaria, and natural history collections for the treatment of insect-infested materials (Florian 1986). More recently, some consideration has also been given to its possible application as an alternative to chemical fumigants for the treatment of insect-infested museum objects in anthropological collections.

Though freezing is generally considered to be a highly effective means of insect control, in reality, very little information exists with regard to the lethal effect of low temperatures upon many of the more common museum pests. Much of the literature is devoted to stored-product pests; moreover, these studies were conducted over a wide range of temperatures and exposure periods (Adler 1960; Back 1924; Cantwell and Smith 1971; Childs et al. 1968; Childs et al. 1970; Crumb and Chamberlain 1934; Gerber 1981; Howe 1957; Knipling and Sullivan 1957; Mullen and Arbogast 1979; Myburgh and Bass 1969; Nagel 1934; Nowosielski-Slepowron and Strevens 1973; Swingle 1938; Tenhet et al. 1957; Waggoner 1985). Only a few systematic studies have been conducted on museum pests (Arevad 1975; Arevad 1980; Ketcham-Troszak 1984).

However, a tentative treatment schedule for the disinfestation of museum objects has been proposed by Florian (1986), who recommended repeated exposures to −20�C for two days. This treatment schedule was derived primarily from a review of the scientific literature on the effect of low temperature on insects as well as from existing freezing procedures used in various museums that have been found to be successful in eradicating insect pests (Crisafulli 1980; Florian 1986; Nesheim 1984). In most cases a commercial freezer was used, which generally operates at this temperature. To avoid freeze-resistance, Florian (1986) recommended a high cooling rate and multiple exposures to sub-zero temperatures.

In the absence of a systematic study of the time-mortality relationship for the major museum pests, it is difficult to establish appropriate treatment procedures for the disinfestation of museum objects. For this reason a study of the lethal effect of prolonged exposure to low temperatures was undertaken for a number of museum pests. The results of the experimental trials for Stegobium paniceum. (Linneaus), commonly refered to as the drugstore beetle, are presented.

Stegobium paniceum is a cosmopolitan pest that may infest almost any dry animal or plant product (Ebeling 1975). Only the larval stage of this species feeds. Within museums it has been known to attack a wide variety of materials including botanical and entomological specimens as well as anthropological artifacts (Kingsolver 1988; Story 1985). The life cycle is dependent upon temperature and humidity, but one or two generations per year is common at room temperatures (Lefkovitch 1967).