Studies on the abundance of Cryptolestes turcicus (Grouv.) (Coleoptera, Cucujidae) in different machines of an English flour mill

Abstract

The relative abundance of Cryptolestes turcicus (Grouv.) in eight centrifugals of an English flour mill was studied during the months preceding the annual fumigation in each of five years. The machine which regularly supported the largest population was that containing the least nutritious stock. It also contained the dampest residues in the only year in which the moisture content of the millstocks was studied. An infestation of over 32,000 C. turcicus was found in this centrifugal on one occasion. Three additional centrifugals, replicating the function of the badly infested machine, contained large infestations and damp or moderately damp residues when examined during one year. The relative abundance of C. turcicus in these machines appeared to depend more on the moisture content of the residues than on the nutritional differences between the free-flowing centrifugal flours passing through them. Large infestations may be dependent on the moulds which develop in damp flour residues. The centrifugal sieves did not form an impassable barrier to mutant C. turcicus released into the feed of two machines.