Wax glands ultrastructure and chemical composition of wax of giant mealybug Drosicha stebbingii (Green) (Hemiptera: Monophlebidae)

Droschia stebbingii (Green) belonging to the family Monophlebidae (Hemiptera: Coccoidea) is a serious, phytophagous and dimorphic pest. D. stebbingii and D. mangiferae (Green) with sixty-two common hosts and minor morphological variations pose problems towards their taxonomic identification. Light and scanning electron microscopy were used to outline the ultrastructural details of cuticular wax producing structures of D. stebbingii. Three types of wax-pores along with tubular duct were observed on the head, thorax and abdomen. Quinquelocular and multilocular disc-pores exhibited variations in the central loculus with single and double opening. Short curly wax strands were secreted from the outer loculi whereas central loculus secreted long tubular strands. Additionally, bilocular pores secreting curly wax were observed having two large loculi separated by a septum. GC–MS analysis of cuticular wax indicated the presence of hydrocarbons and wax esters forming majority of the covering along with long chain alcohols, ketones and acids. Variations in the percentage of hydrocarbon and wax esters content were observed for two populations of D. stebbingii collected from different hosts. Hydrocarbons were abundant in populations collected on Pongamia pinnata (L.) Pierre whereas long chain esters dominated the wax profile for the population collected from Tectona grandis L.f. Compositional variations in the cuticular wax of D. stebbingii on different host along with knowledge on the ultrastructural wax pores and waxy secretion would provide an insight to the existing knowledge of this scale insect.