Discochiton rotundum Green
Creators: name: Chris J. Hodgson
name: Douglas J. Williams
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hemiptera
Coccidae
Discochiton
Discochiton rotundum

description: Discochiton rotundum (Green) comb. & stat. n.
(Fig. 22)
Lecanium expansum rotundum Green, 1904a, 206. Type data: INDONESIA: Java, on Rhizophora mucronata. Syntypes, female. Type depository: BMNH, London, England, U.K.
Paralecanium expansum rotundum; Sanders, 1906, 9. Change of combination.
Material examined. Lectotype f (here designated): INDONESIA, Java: top labels: TYPE in red on small round label + Lectotype on a narrow label; bottom label: Lecanium / expansum / var. rotundum Green / from / Rhizophora mucronata / Java / coll. Zimmermann No. 82. (BMNH): 1/1adf (p; fairly young, missing most of venter). Java: bottom label: Lecanium / expansum / var. rotundum Green / from / Rhizophora mucronata / Java / coll. Zimmermann No. 82. (BMNH): 1/1adf (p, missing most of venter).
Other material. MALAYSIA, Kuala Lumpur, no host, 18.iv.1943, R. Takahashi (BMNH): 1/2adff (fp; identified as P. vacuum Morrison). Selangor, Port Swettenham, on Rhizophora sp., -. xii.1943, H. Takahashi (BMNH): 1/2adff (fp; identified as P. vacuum Morrison).
Note. The description is based on both Javan specimens; data in […] brackets are from the Malaysian material where different.
Unmounted material. “Smaller than type [P. expansum] and round in outline. Margin stippled as in metallicum.” (Green 1904, p. 206).
Slide-mounted adult female. Body almost round. Length 5.2–5.5 [3.5–5.0] mm, width 5.0 [3.0–4.5] mm.
Dorsum. Derm slightly sclerotised on one specimen and with a narrow unsclerotised marginal band about 100– 150 µm wide; with a band of short ridges or areolations parallel with margin submarginally but elsewhere derm rather uniformly sclerotised with numerous very small pale spots about 1 µm wide. Marginal radial lines not apparent but indicated by pore and setal distribution, with probably 13 radial lines of setae on head, each side possibly with 5 between stigmatic clefts and 12 or 13 along abdominal margin. Abdominal clear areas numbering 4 pairs plus an additional pair near apices of each anterior stigmatic ray. Dorsal setae each spinose with a capitate apex, 8–10 µm long with a basal socket about 5 µm wide; many setae each closely associated with an approximately round, pale area of derm about 20 µm wide; frequent sparsely in a polygonal pattern in a broad marginal band extending medially to about level with clear areas; setae absent medially. Preopercular pores each small and convex, 3–4 µm wide, present as follows: CA1 with 0 [2–4] pores, CA2 & CA3 each with 17–22 [9–19] and CA4 with 0 pores. Other dorsal pores of possibly two sizes present: (i) larger pale areas of derm each surrounded by a band of short ridges or areolations, present more or less throughout but absent medially; these may be membranous areas of derm around each dorsal seta; and (ii) small simple pores or microducts present close to some marginal setae and also medially, appearing as small clear spots. Anal plates rather small and triangular, together narrowly quadrate, with anterior and posterior margins subequal in length and outer angle sharp; each plate with 3 minute setae near posterior apex plus 1 small pore medially; length of plates 300–310 [269–310] µm, combined width 205–215 µm. Anogenital fold with 2–5 [2–4] minute setae at each corner of anterior margin, each lateral margin with 1 seta anteriorly and another posteriorly.
Margin. Marginal ornamentation: groups of short dark radial lines with shallow indents between groups; each radial line extending medially to about same depth as inner end of socket of each marginal seta; mostly with 3 or 4 groups between marginal setae. Marginal setae broadly fan-shaped; width of each fan about 40–50 [33–45] µm, length 40–42 [33–35] µm; with about 137 [129] setae anteriorly on head between anterior stigmatic clefts, each side with 62–65 [43–52] between stigmatic clefts and 110–132 [102–104] on abdomen. Stigmatic clefts quite deep, each with a narrow entrance, a sclerotised inner margin and 3 elongate, blunt stigmatic spines of subequal length; all spines broadest basally but only narrowing slightly to apex; length of each spine 33–50 µm. Eyespots: each with socket oval, maximum width 35–40 µm, diameter of lens 7.5–8.0 µm.
Venter. Derm membranous; marginal band probably absent. Multilocular disc-pores frequent on either side of genital opening and on preceding two segments only, each side with 26–33 [16–31] pores on abdominal segment VII, 55–60 [30–53] on segment VI and 40–49 [30–51] on segment V. Spiracular disc-pores present in a narrow band mostly 1 pore wide between margin and each spiracle, with 38–42 [13–20] pores in each band (each posterior band without pores in a short middle section). Ventral microducts minute, present just posterior to mouthparts; probably present elsewhere but very sparse. Ventral setae: with 1 or 2 pairs of setae between antennae and with pairs of long pregenital setae on segments VII–V (that on VII 108 µm long); small setae frequent medially just anterior to vulva in abdominal segment VII, otherwise very sparse; submarginal setae perhaps present in radial bands, as on dorsum. Antennae reduced (only 1 present), 3 segmented (segmental divisions between segments III– VI absent); total length 132–134 µm; setose setae absent from apical segment. Clypeolabral shield 140 [105] µm long. Spiracles: width of each peritreme 55–57 [48–50] µm. Legs entirely absent.
Comments. Adult female D. rotundum are extremely similar to those of D. expansum but differ as follows (data for D. expansum in brackets): (i) preopercular pores present associated with only CA2 and CA3, rarely also CA1, but absent from CA4 (most abundant associated with CA4); (ii) complete absence of legs (present as small stubs), and (iii) only 3 stigmatic spines per cleft, each narrowing to a blunt apex, relatively short (sometimes more than 3 spines, each parallel sided and longer). Although these differences are small, it is here considered this represents a separate species, D. rotundum (Green), stat. n. The specimens from Malaysia are extremely similar to the type series but differ in (i) having far fewer spiracular disc-pores, and (ii) the presence of a few preopercular pores associated with the anteriormost clear areas on the abdomen. Discochiton rotundum is somewhat similar to D. metallicum but has narrow spiracular disc-pore bands, whereas D. metallicum has broad bands. D. rotundum is also similar to D. quadratum, but this latter species has setose dorsal setae.
Host-plants. Rhizophora mucronata (Rhizophoraceae).
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 61-63, DOI: 10.11646/zootaxa.4443.1.1, http://zenodo.org/record/1305628