POPULATION VARIABILITY IN A DOMESTIC STORED PRODUCT PEST, THE PARTHENOGENETIC PSOCID LIPOSCELIS BOSTRYCHOPHILA: IMPLICATIONS FOR CONTROL

Abstract:
The small (1mrn long), wingless, psocid, Liposcelis bostrychophila (Badonnel) (Psocoptera, Liposcelidae), is found throughout the world and is frequently a pest of farinaceous food stores. Since the early 1940's, when this insect was recorded for the first time in southern England, it has spread to virtually all parts of the UK where it is now a major cause of consumer complaints in some areas of the food industry. L. bostrychophila is parthenogenetic and, for its size, relatively long lived. It displays considerable adaptability to deal with local or temporary situations. Adults have a wide temperature tolerance, a very catholic diet and an ability to go for long periods without food. In good conditions they maximise reproductive output whilst in poor conditions their egg output reduces or stops whilst their longevity increases. These two alternatives are readily switchable in fluctuating conditions. In addition they show some tolerance to pyrethroid insecticides. Parthenogenesis is essentially a clonal mode of reproduction and yet there is a considerable degree of variability in the biologies of individuals of the same clonal line. Advantageous traits, resulting from random mutations, will be readily incorporated into the genotype of a parthenogenetic species and so spread rapidly, at least on a local scale. At the individual level allozyme variations can be seen within and between populations from different localities in the UK. These are being used to attempt to identify particular features of this liposcelid's biology. The problems of controlling L. bostrychophila are discussed in the light of this population variation.