Discochiton pseudexpansum, comb. n.
Creators: name: Chris J. Hodgson
name: Douglas J. Williams
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hemiptera
Coccidae
Discochiton
Discochiton pseudexpansum

description: Discochiton pseudexpansum (Green) comb. n.
(Fig. 20)
Lecanium pseudexpansum Green, 1914, 233. Type data: AUSTRALIA: Northern Territory, Koolpinyah, near Darwin, on Pandanus odoratissimus. Syntypes, female. Type depository: BMNH, London, England, U.K.
Paralecanium pseudexpansum; Ben-Dov, 1993, 207. Change of combination.
Material examined. Lectotype f and paralectotype ff (here designated): AUSTRALIA, bottom label: Lecanium / pseudexpansum / Green / on Pandanus / Darwin, N.T. / Australia / ex coll. G.F. Hill (BMNH): 1/3adff (fg; all with damaged venters; holotype top left-hand specimen). Australia: top label: TYPE; bottom label: Lecanium / pseudexpansum / Green / from Pandanus / Koolpinyah / Nr. Darwin, N.T. / Australia / ex coll. I.E.B. No. 4 / Darwin, N.T. / Australia / ex coll. G.F. Hill (BMNH): 1/4adff (fg-p, venter often damaged or missing). Australia: top label: Darwin / N. Territory / Australia / G.F. Hill / 1914 - 478; bottom label: Lecanium / pseudexpansum / Green / from Pandanus / Koolpinyah / Nr. Darwin, N.T. / Australia / ex coll. I.B.E. No. 4 (BMNH): 1/5adff (venter mainly badly damaged; possibly part of type series).
Other material. Australia, labelled Lecanium pseudexpansum Green, Northern Territory, Darwin, on Pandanus odoratissimus, 22.iv.1922, ex coll. E.E. Green (mounted by Hall) (BMNH): 1/2adff (fg, 1 mature and 1 young). Australia: as previous but #14685: Lecanium pseudexpansum Green, Pandanus odoratissimus, letter June 5, 1916, G.F. Hill, ex collection of E.E. Green (USNM): 1/3adff (all probably young; f, but venter of all specimens damaged although all structures visible on at least one specimen. This is not a type slide as the specimens were collected 2 years after the description was published).
Note. The description is based on all the specimens, as few have a venter.
Unmounted material. ‘ Adult female broad and flat; broadly oval, often of very irregular outline. Colour pale fulvous to ochreous; often marbled with dark brown, and usually with a submarginal narrow dark brown zone. Surface (under magnification) minutely pustulate; appearing smooth and shining to the naked eye, but with indications of shallow polygonal depressions covered by glassy concentrically marked plates of colourless secretion.’ (Green 1914, p. 233).
Slide-mounted adult female. Body oval to almost round. Length 2.8–5.5 mm, width 2.0– 4.5 mm.
Dorsum. Most specimens young, with derm apparently membranous; all specimens with a submarginal band of pale oval areolations, most areolations each 10–14 µm wide. Marginal radial lines not clear but indicated by distribution of dorsal setae and pores, with perhaps 13 around head, each side with 5 between clefts and 13 on abdomen; stigmatic rays present. Distribution of pores and setae suggesting an obvious polygonal pattern on youngest specimen. Abdominal clear areas numbering 4 pairs plus another at inner ends of anterior stigmatic rays. Dorsal setae each quite long and setose, with a pointed apex, each 15–25 µm long (longest submedially) with a broad basal socket 5–6 µm wide; frequent submarginally and submedially but absent medially; in radial lines near margin. Preopercular pores, each 4–5 µm wide and possibly strongly convex, often each with clear micropores; all clear areas with 7–15 pores. Other dorsal pores hard to see, but some present submarginally, each with a pale central area about 3 µm wide surrounded by circles of ridged derm; often associated with a dorsal seta. No other pores noted. Anal plates together quadrate, each plate with posterior margin slightly longer than anterior margin and with 3 small setae near apex plus a longer apical seta, 25–37 µm long; position of anteriormost seta rather variable, often placed towards centre of each plate; without small pores medially; length of plates 165–212 µm, combined width 145–182 µm. Anogenital fold with 2–3 minute setae at each corner of anterior margin, each lateral margin with 1 anteriorly and another posteriorly.
Margin. Ornamentation present as a narrow border of groups of short radial ridges or crenulations. Marginal setae all spinose but very variable in shape, with some blunt and more or less parallel-sided, some strongly divided and some almost club-shaped; setae not constricted basally within an invaginated basal socket; seta length 13–25 µm; with 39–63 setae anteriorly on head, each side with 14–24 between stigmatic clefts and 30–49 on abdomen. Stigmatic clefts quite deep, each with a narrow entrance and a narrowly sclerotised inner margin, with 3 (rarely 4 or 5) blunt stigmatic spines, median spines each 35–65 µm long, lateral spines slightly shorter, each 35–44 µm long but, when more than 3 spines/cleft, with 1 or more spines only 20 µm long. Eyespots each with diameter of lens about 26–32 µm.
Venter. Derm membranous, without a fairly broad marginal band or fold. Multilocular disc-pores abundant around genital opening and on preceding two segments only, each side with 21–33 by vulva, 21–35 in segment VI and 14–19 in segment V. Spiracular disc-pores present in a narrow band between margin and each spiracle, with 30–34 pores in each band; posterior bands each without an obvious gap in middle of pore band. Ventral microducts minute, present in a dense group just posterior to and on either side of labium; presence elsewhere unknown. Ventral setae: with 2 pairs of long setae between antennae and pairs of long pregenital setae on abdominal segments VII–V; small setae frequent medially just anterior to vulva in abdominal segment VII, otherwise very sparse, and submarginal setae not located. Antennae reduced, 6-segmented but with segmentation sometimes indistinct; total length 160–185 µm. Clypeolabral shield 140–165 µm long. Spiracles: width of each peritreme 50–66 µm. Legs present, represented by small stubs.
Comments. Of the species covered here, D. pseudexpansum is unique in having spinose, non-fan-shaped, marginal setae. Despite this, it is considered to belong to this genus, as indicated by Froggatt’s (1915) observation: “...closely allied in colour, structure, form and size to Lecanium expansum, but differs in having simple marginal setae instead of flabelliform setae ...”. Other significant features are: (i) presence of preopercular pores associated with all four CA, and (ii) long setose dorsal setae.
Discochiton pseudoexpansum appears to be restricted to Australia where it has been collected only early in the last century, in the Northern Territory.
Host-plants. Pandanus sp., Pandanus odoratissimus (Pandanaceae).
description: Published as part of Chris J. Hodgson & Douglas J. Williams, 2018, Revision of the soft scale genus Paralecanium (Hemiptera: Coccomorpha: Coccidae) with the introduction of three new genera and twenty new species, pp. 1-162 in Zootaxa 4443 (1) on pages 56-58, DOI: 10.11646/zootaxa.4443.1.1, http://zenodo.org/record/1305628