MacGillivray, 1921
Appearance in life
Scale cover of adult female circular to oval or very broad mussel-shell-shape, more or less convex, white to greyish white, with colourless to brown exuviae subcentral or marginal. Scale cover of immature male different from that of female; small and elongated, white, felted, with terminal exuviae.
Morphology
Adult female not pupillarial; body turbinate or more or less fusiform, widest between mesothorax and abdominal segment I, then tapering to apex of pygidium. Derm membranous except for pygidium; free abdominal segments more or less lobed laterally, without marginal sclerotized spurs. Pygidium more or less rounded, sometimes with a distinct apical notch. Median lobes usually well developed, zygotic, with a pair of marginal setae between the bases; variably shaped according to species and sometimes also related to substrate; sometimes strongly divergent and elongate, forming a notch in apex of pygidium (as in many leaf-forms); may be separated, sometimes by a gap wider than a median lobe; or parallel at the base and divergent distally, or broad and close together, then more or less divergent (as in many bark-forms); apically rounded or serrated. Second lobes smaller than median lobes, bilobed (but outer lobe sometimes obsolete). Third lobes present or absent. Small ventral paraphyses in some species arising from the angles of the inner lobules of second and sometimes third lobes, usually converging anteriorly. Gland spines large; in some species, those on pygidium with branched tips and up to 3 microducts in each one; absent from between the median lobes; usually present singly or in pairs between the lobes, simple gland spines present also on abdominal segments V and IV at least; also present, or replaced by ventral conical duct tubercles, on segments further forward. Anus circular, usually situated between centre and anterior 1/3 of pygidium; vulva situated at, or fairly near, centre of pygidium. Marginal macroducts same size as dorsal ducts or slightly larger, each orifice with the long axis perpendicular to the margin; sometimes associated with small pore prominences or marginal serrations; usually numbering 6 or 7 on each side of the pygidium (1 between median and second lobe, 2 by third lobe, 2 on segment V and 1 or 2 on segment IV), absent from between median lobes. Dorsal macroducts about same size as marginal ducts or slightly smaller, arranged in segmental rows of submarginal and submedian ducts along posterior margins of segments; usually present as far back as submargin of segment VI but absent from segments VII or VIII. Dorsal macroducts with elongate-oval orifices; in some species, submedian macroducts sometimes accompanied, or replaced, by microducts. Submarginal dorsal bosses sometimes present on either side of abdominal segment I. Ventral duct tubercles may be present anterior to abdominal segment IV. Perivulvar pores usually numerous, present in 5 groups. Stigmatic disc pores present in a compact cluster by anterior spiracle; fewer by, or absent from, posterior spiracle. Antennae often situated quite near anterior margin and set quite close together; each antenna with 1 fleshy seta.