Biochemical profiling of epidermal body wax and honeydew excretions in polyphagous mealybug species

Mealybugs (Hemiptera: Pseudococcidae) are vulnerable soft bodied insects protected by an external hydrophobic wax coating, which shields them from extreme temperatures and pesticide applications. This study characterized the biochemical composition of mealybug body wax and sugar profile of honeydew, viz., Maconellicoccus hirsutus Green, Planococcus citrii Risso, Ferrisia virgata Cockerell, Rastrococcus iceryoides Green. Gas chromatography-mass spectrometry and liquid chromatography with tandem mass spectrometry profiling, revealed that mealybug body wax is primarily composed of long-chain hydrocarbons, alcohols, esters, aldehydes and ketones. The major hydrocarbons detected included phenyl tetramethyl cyclopentadiene, 1,19-eicosadiene tetratriacontane. Key wax esters identified included ä-methyl-2-(2-hydroxyethyl)-2-devinylchlorine 6 trimethyl ester, with notable interspecies variation in hydrocarbon composition. The honeydew primarily composed of sugars such as fructose, glucose and sucrose, with distinct dominance patterns among species. Rastrococcus iceryoides had glucose as the dominant sugar (32.12 g/100 g of honeydew), while fructose was most abundant in M. hirsutus (25.18 g/100 g) and P. citrii (16.1 g/100 g). Understanding the biochemical makeup of mealybug body wax and honeydew composition could aid in developing new management tactics for controlling these notoriously hard-to-kill pests.