An experimental study of morphological variation in mealybugs (Homoptera: Coccoidea: Pseudococcidae)

Abstract Cultures of a number of species of mealybug were reared under a variety of controlled environments and the effects of factors such as temperature, relative humidity and host plant on the morphology of the adult females examined. It was found that temperature had the greatest effect. The lengths of the appendages and setae, and the numbers of wax producing pores and ducts, vary over a wide range within a single species when specimens are reared at different temperatures. The relationship with temperature is generally linear, with size and pore numbers increasing with decreased temperature. However, some characters, noticeably the numbers of tubular ducts, reach their highest values at an intermediate temperature. It is suggested that while variation in size is a direct response to temperature, other characters are influenced by size or by a combination of size and environmental factors acting independently. Rearing mealybugs under different environmental conditions in order to induce morphological variation is shown to be a useful technique for resolving difficult species complexes.