Ultrastructure of Ericerus pela (Chavannes) nymph mouthparts and ecological adaptations

The ultrastructure of nymph mouthparts of the Chinese white wax scale (CWWS), Ericerus pela, consists internally of the crumena, tentorium, the stylet bundle, comprised of two mandibular stylets and two maxillary stylets, and the external clypeolabral shield, labium and sensilla. The mouthpart morphology and structures of the female nymphs are similar to the male. The mouthparts of CWWS have significantly different features in comparison to aphids and other coccids. First, the mouthparts of CWWS have a crumena and a developed tentorium. Second, the labrum is highly degraded and the labium is short and one-segmented. Third, the maxillary stylets have two ‘T’ type locks. Lastly, the hairs of the mouthpart are sparse and the sensilla are simple. As the labrum and labium of CWWS displayed a high degree of degradation and the tentorium was found to be highly developed, the stretching of the stylet bundle was considered to be controlled by the tentorium and crumena together. Furthermore, the degraded sensilla may be related to a specialization of feeding behavior. There were no significant differences in the length and diameter of the stylet bundles between the female and male. However, the length and diameter of the stylet bundles were significantly different between the first instar nymphs and the second instar nymphs. The first instar nymphs had stylet fascicles that were shorter and soft and initially lived on the leaves of the host trees, presumably because the leaves were thinner and they were able to pierce the leaves while the stylet bundle was relatively soft. However, the second instar nymphs had stylet bundles that were relatively hard. After the numphs molted, the degree of ossification of the stylet bundles was enhanced (increased) and the nymphs returned to the branches for living, where the strengthened stylet bundles may provide a better adaption for the thicker bark. All told, the first and second stage instar CWWS nymphs switched from leaves to the branches in order to find a safe habitat and stable food source.