The hinged back plate mechanism in glassy wax tests of New Zealand male soft scale insects (Hemiptera: Coccoidea: Coccidae).
Male scale insects (Hemiptera: Coccoidea) undergo a metamorphosis of the neometabola type, from scale-like nymph through prepupa and pupa to winged adult. The nymphal instar before prepupa secretes a waxy protective covering that remains in place throughout metamorphosis and these covers are characteristic of each family of scale insects. Most scale insect families (e.g. mealybugs, eriococcids, diaspidids) have rather loosely woven male covers, but male nymphs in the family Coccidae (soft scales) construct more rigid, glassy wax tests, which need a special mechanism for adult emergence. In the New Zealand male soft scales, a suture across the posterior quarter of the test enables the back plate to flex at a pair of hinges, to be raised up off the substrate, and so allow egress. The waxy back plate hinges are secreted by groups of tubular ducts on the abdominal dorsum of 2nd-instar males, during construction of the test. Scanning electron micrographs (SEMs) show the detail and diversity of hinge types. The wax tests of most New Zealand Coccidae, both female and male, are apparently unique in that they are constructed in rows of hexagonal plates, separated by sutures, however in the male test, the sutures are all fused except for the back plate suture. The two species in the endemic New Zealand genus Pounamococcus have male tests more like those of species in the Australian genus Austrolecanium.
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