Physicochemical mechanisms for the removal of insect wax by means of finely divided powders

Abstract

does not appear. First page follows. Introduction About 95 per cent of the insect cuticle consists of a relatively thick inner part called the procuticle, composed of chitin, protein, and other compounds, and containing considerable quantities of water. Above the procuticle is the nonchitinous epicuticle, approximately 1 ? in thickness, which consists of an inner hydrophylic protein zone, called the cuticulin, a middle zone composed of lipid (usually a solid wax), and an outer zone of shellaclike material, the so-called “tectocuticle” or “cement” (Richards, 1951).3(Beament (1959)) found that with some insects, wax in a volatile solvent migrates through the cement to form an outer layer of wax. It is the lipid of the epicuticle that protects insects from abnormally rapid loss of water. A number of investigators have shown that when insects or mites crawl over films or layers of finely divided particles, particularly when the latter are deposited as dry dusts, they are susceptible to desiccation. This desiccation results from the removal by these particles of some of the very thin lipid layer of the epicuticle (Zacher and Künicke, 1931); (Hockenyos, 1933); (Germar, 1936); (Zacher, 1937a), (1937b); (Chiu, 1939); (Alexander et al., 1944); (Kalmus, 1944); (Parkin, 1944); (Wigglesworth, 1944), (1945), (1947a), (1947b), (1957), (1958); (Beament, 1945), (1958); (Hunt, 1947); (Cotton and Frankenfeld, 1949); (David and Gardiner, 1950); (Bartlett, 1951); (Helvey, 1952); (Glynne Jones, 1955); (Holdgate and Seal, 1956); (Nair, 1957); (Ebeling and Wagner, 1959); (Wagner and Ebeling, 1959); (Tarshis, 1959), (1960), (1961); and (Micks, 1960). Some investigators have attributed the desiccating action of finely divided powders primarily or entirely to their ability to remove the protective lipid layer by abrasion (Wigglesworth, 1945), (1947a), (1958); (Beament, 1945); (Hunt, 1947); and (David and Gardiner, 1950)). (Beament (1959)) later reiterated his belief that stationary adsorptive powders applied to the “primary” wax layer do not increase its permeability to water, but that when applied