Abstract:

The ultra-morphology and chemical composition of waxes secreted by the scale insects, Ceroplastes ceriferus (Fabricius) and C. japonicus Green (Homoptera: Coccidae) were studied with the techniques of scanning electron microscope (SEM) and gas chromatography/ mass spectrometry (GC/MS). The results indicate that the two wax scale insects have a similar waxy secretion and wax test forming process. The scale insects in their first and second instars secreted dry wax that formed a star-shaped test. Every wax horn around the margin of the test consists of two segments. This is corresponding to the two developmental instars. Furthermore, each of the two segments of the wax horn included many sub-segments. Meanwhile, the wax accumulated into a cap-like structure with many layers on the dorsal region of the body. It was believed that some kind of rhythm existed in the wax secreting. A lot of striate punctures formed wax glands that are usually unable to be found with the slide specimens of the wax scale insects observed under the light microscopy. As the scales developed into the 3rd instar and adult stage, the wax secretion changed into “wet state" and formed a waxy test in tortoise shell shape. The wax glands on the dorsal surface mainly are trilocular and quadrilocular pores. Dense wax pores arranging in longitudinal strips also were found over the anal plates. The main chemical compositions of the wax secretions of the two scale insects were determined with GC/MS by the two methods of esterification and unesterification. For C. ceriferus, 14 and 14 compounds were determined from its wax secretion with the two methods respectively; while 10 and 25 compounds were determined respectively from the wax secretion of C. japonicus. The main compositions of their wax secretions include a series of long chain saturated and unsaturated hydrocarbons, fatty acids, fatty alcohol, esters, and some compounds with ring structures of multi-, macro-, or heterocyclic ring. Their biological functions were discussed.

Key words: Coccidae, Ceroplastesceriferus, Ceroplastesjaponicus, wax secretion, ultra-morphology, chemical composition