Discochiton seychellarum Williams & Hodgson

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, Zootaxa 4443 (1), pp. 1-162 : 66-69

Discochiton seychellarum Williams & Hodgson spec. n.

( Figs 24 and 25 )

Paralecanium sp. Vesey Fitzgerald, 1953: 409.

Material examined. Holotype f: SEYCHELLES: left label: SEYCHELLES / Anse á la Mouche / on coconut / coll. E.S. Brown / 2354a / 12689; right label: Paralecanium [crossed out] / Discochiton / seychellarum / Williams & Hodgson / Holotype f ( BMNH): 1/1adf (f-g).

Paratypes ff: left label: SEYCHELLES / Anse á la Mouche / on coconut / coll. E.S. Brown / 2354a / 12689; right label: Paralecanium [crossed out] Discochiton / seychellarum / Williams & Hodgson / paratype f ( BMNH): 5/5adff (fp, most missing venters).

Other material. SEYCHELLES, Mahé, Anse Boileau, 30.vi.1937, on coconut, Vesey Fitzgerald ( BMNH): 2/2adff (p, but with some venter). Seychelles: Silhouette, Jardin Marron, on Phoenicophorium sp., 26.i.2001, Justin Gerlach ( BMNH): 5/5 adff (f, venter present on only 1 specimen).

Note. The description is based on all type specimens; data for specimens off Phoenicophorium sp. are given in […] where different.

Slide-mounted adult female. Body elongate oval. Length 5.5–7.0 [4.5–6.2] mm, width 3.2–4.4 [2.5–3.5] mm.

Dorsum. Derm rather uniformly sclerotised medially, with many minute small spots forming a distinct polygonal pattern; derm with a few areolations submedially. Marginal radial lines indicated by pores and setae, with 13 lines anteriorly on head, each side with 5 between clefts and 13 on abdomen; stigmatic rays present. Abdominal clear areas numbering 4 pairs. Distribution of dorsal setae and dorsal pores suggesting a sparse polygonal pattern. Dorsal setae each finely spinose, mostly with a blunt apex but sometimes more pointed, 16–18 [10–13] µm long with a broad basal socket about 5 µm wide; each seta situated in an area of derm with ridges in a whorl, rather pore-like. Preopercular pores small and convex, each pore 5–7 [3–4] µm wide, distributed as follows: CA 1 12–24 [7–11], CA 2 15–29 [3–12], CA 3 11–28 [6–13] and CA 4 16–29 [6–11] pores. Dorsal pores of two types present: (i) small simple pores, appearing as small non-sclerotised spots, each 1.5–2.0 µm wide, rather randomly distributed, possibly similar pores present just dorsad to some marginal setae; and (ii) quite small sclerotised pores, which might be bilocular, each about 3 µm wide, also rather randomly distributed. Anal plates elongate, together narrowly quadrate, with anterior and posterior margins subequal in length; each plate with 4 or 5 minute setae near posterior apex and 1–3 small pores medially or sometimes near outer margin; length of plates 235–250 [185–205] µm, combined width 180–195 [130–150] µm. Anogenital fold with 4–6 minute setae at each corner of anterior margin, each lateral margin with 1 seta anteriorly and another posteriorly.

Margin. Ornamentation: very short dark radial lines. Marginal setae broadly fan-shaped; width of each fan about 38–45 [35–50] µm, length 25–40 µm; with about 124–158 [104–150] setae anteriorly on head between anterior stigmatic clefts, each side with 46–71 [42–57] between stigmatic clefts and 1 02–137 [92–133] on abdomen. Stigmatic clefts quite deep, each with a narrow entrance, a sclerotised inner margin and 5–9 [3] elongate, blunt stigmatic spines; more anterior spines in each cleft often longest [median longest]; length of spines 25–50 µm. Eyespots: each socket 95–115 µm wide, diameter of lens 20–25 µm.

Venter. Derm membranous; ventral marginal band absent. Multilocular disc-pores frequent on either side of genital opening and on preceding two segments only, each side with 14–22 on abdominal segment VII, 25–36 on segment VI and 1–21 on segment V. Spiracular disc-pores present in a narrow band mostly 1 pore wide between margin and each spiracle, with 32–49 pores in each band; posterior band with disc-pores very sparse medially and near spiracle. Ventral microducts minute, present in a dense group just posterior to and on either side of labium; sparse elsewhere. Ventral setae: with 2 pairs of interantennal setae; pairs of long pregenital setae in segment VII and shorter setae in VI & V (that in VII 100–120 [90] µm long); a group of about 10 moderately long setae on each side (each about 20 µm long) laterad to anterior end of anal cleft; small setae frequent medially just anterior to vulva in abdominal segment VII, otherwise very sparse; and submarginal setae sparse and short. Antennae reduced, each with 3 segments (segmental divisions between segments III–VI absent); total length 120–145 [165–178] µm; without hair-like setae on fused apical segment. Clypeolabral shield 135–145 [125–130] µm long. Spiracles: width of each peritreme 50–65 [41–45] µm. Legs absent.

Comments. Adult female D. seychellarum Williams & Hodgson spec. n. resemble some D. expansum specimens in having frequently more than 3 stigmatic spines in each stigmatic cleft. However, D. seychellarum differs from D. expansum in lacking leg stubs, in having sharply spinose dorsal setae and preopercular pores associated with all abdominal clear areas.

The specimens off Phoenicophorium sp. differ significantly from those off coconut. In particular, specimens off the former plant have only 3 stigmatic spines per stigmatic cleft whereas those off coconut have up to 9 per cleft; in addition, specimens off Phoenicophorium have shorter anal plates, fewer preopercular pores per clear area, longer antennae and smaller spiracles. It could be argued that these differences (particularly in the number of stigmatic spines) are enough to separate the two lots of material; however, the view is taken here that it is unlikely that 2 species would evolve sympatrically on Arecaceae species on these islands, so they are here being treated as a single species.

Host plants. Cocos sp., Phoenicophorium sp. ( Arecaceae ).

Name derivation. This species is named after the group of islands in the Indian Ocean on which they were collected.

Figures

FIGURE 24. Discochiton seychellarum Williams & Hodgson, spec. n., adult female. Type series, Mahé, Anse à la Mouche, Seychelles.

FIGURE 25. Discochiton seychellarum Williams & Hodgson, spec. n., adult female. Jardin Marron, Silhouette, Seychelles.