Discochiton expansum (Green)
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: 28-32
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|Discochiton expansum (Green)|
Discochiton expansum (Green) comb. n.
Lecanium (Paralecanium) expansum ; Cockerell & Parrott, 1899, 227.
Paralecanium expansum ; Fernald, 1903: 199. Change of combination.
Material examined. Lectotype f and paralectotype ff (here designated): SRI LANKA (as Ceylon): top labels: oval label: Co-type; narrow label: Lectotype in red; bottom label: Lecanium / expansum / Green / from Litsea / Pundaluoya / Ceylon (BMNH): 1/2adff (f-g) + 1 second/third-instar f (fp) (lectotype smallest adult female nearest data label, arrowed). Sri Lanka: top label: labelled Type in red on round label; bottom label: Lecanium / expansum
/ Green / from Litsea zeylanica / Pundaluoya / Ceylon ( BMNH): 1/1adf, but lacking most of venter (f); bottom label: Lecanium / expansum / Green / Pundaluoya / Ceylon ( BMNH): 1/2adff (f-g; probably part of type series).
Other material. AUSTRALIA, Queensland, Bundaberg (as Bundabery), on Ficus sp., 28.vii.1910, W.W. Froggatt #60 (USNM): 1/1adf (labelled Lecanium expansum javanicum (Green) (f, but venter somewhat damaged and displaced to one side but with a leg stub; misidentification). Australia, as previous but labelled just Queensland, on Ficus sp. W.W. Froggatt (BMNH): 1/3 adff (f-p, two missing most of venter and third with venter damaged; misidentification).
CHINA, HONG KONG, Braemar Hill Road, Choi Sai Woo Park, on Litsea sp., 1.xii.2003, S.K. Lau & J.H. Martin 7887A ( BMNH): 1/1adf (g) + 1/1adf + 4 first-instar nymphs. Hong Kong, Pokfulam, ex Ficus microcarpa , 3.iv.1974, D.S. Hill ( BMNH): 2/2adff (1 vg, 1 missing venter). Hong Kong, Tai Tam Country Park, on Dendrotrophe frutescens , 28.xii.1991, C.S.K. Lau ( BMNH): 1/1adf (no venter).
INDIA, Mysore, on Ficus retusa , no date, H.M. Lefroy (BMNH): 1/4adff (f-g). Vellayani, on Polyalthia pendula , 24.ii.1978, A. Visalakshi (BMNH: CIE 10220): 1/1adf (fg). Kerala, Vellayani, on Polyalthia sp., 7.vi.1983, Vellayani College of Agric., code no. PLH 161-84 (BMNH, CIEA 15448): 2/3adf (g). Bangalore, on unidentified tree, 1.ix.1982, coll. M.M. (BMNH): 1/4adff (2 missing venter, others fg).
INDONESIA, Sulawesi Utara, Dumoga-Bone N.P., nr Labuanuki , north coast mangrove, on? Bruguiera sp., 8.iii.1985, J.H. Martin #4598 ( BMNH): 1/1adf (f).
PAPUA NEW GUINEA, Morobe Prov., Coast, Buso, on upper leaf surface of unidentified woody plant, 16.ix.1979, J.H. Martin #2572 (BMNH): 1/1adf (g, dorsum and venter separate). PNG, as previous, on upper leaf surface of Gymnacranthera sp., 15.x.1979, J.H. Martin #2710 (BMNH): 1/1adf (fg). PNG, Madang Agric. Stn., on Annona [spelt Anona ] reticulata , 6.ix.1962, Szent Ivany #4772 (BMNH: CIE C332): 3/6adff (fg-p).
SRI LANKA (as Ceylon), Trincomali (Trincolmalee), on Mimusops sp. -. ix.1910, E.E. Green (BMNH): 1/3adff (f-g). Pundaluoya, on Dalbergia championii , no date, E.E. Green (BMNH): 1/1adf (f). Peradeniya, on Myristica fragrans , May 1909, no coll. (BMNH, 14368): 1/2adff (fg). Batticaloa, on Hemicyclea [ Hemicyclia ] sp, -. v.1906, E.E. Green (BMNH): 2/6adff (g-p). Kotta, on unknown host, no date, G. Henry (BMNH): 1/2adff (fg).
THAILAND, Phang Nye Province, forest, near Khao Lak Village, on leaf of bush, 8.xi.2013, I Gavrilov- Zimin ( ZIAS, KN 1121): 1/2adff (g) (also 2/4adff not seen but with same collection data in ZIAS).
VIETNAM (as Indo China), Annam, Tourake, on Viscum orientale, May-July 1927 , J & M.S. Clemens # 3352 ( BMNH): 1/1adf (g).
Note. The following description is based primarily on the type series from Sri Lanka.
Unmounted material. ‘A very large flattish species. Longest diameter nearly 1/ 3 inch.’ ( Green, 1896, p. 9). A large coccid with margin very pale, then a black border, then greenish with darker markings in the posterior half (J. Martin, pers. com.).
Slide-mounted adult female. Body almost round. Length 3.0– 6.5 mm, width 2.5–5.5 mm.
Dorsum. Derm rather uniformly sclerotised, with a fairly broad band of elongate areolations close to margin, long axis of each areolation parallel with margin; inner submargin with small oval areolations, these absent or indistinct submedially and medially; rest of derm with abundant minute pale spots (on some non-type specimens forming a faint polygonal pattern); stigmatic rays present. Marginal radial lines obscure, indicated by distribution of pores and setae, with 13 on head between anterior stigmatic clefts; each side with 5 between stigmatic clefts and 13 on abdomen. With 4 (or rarely 5) pairs of abdominal clear areas submedially and another at apices of anterior stigmatic radial rays. Dorsal setae each spinose, with parallel sides and often apex slightly capitate, each 10–13 µm long (those submedially sometimes significantly longer, each about 20 µm long and without a capitate apex), each with a broad basal socket about 5 µm wide; those located submarginally and submedially each in a membranous area of derm about 10–12 µm wide; frequent in a sparse polygonal pattern, frequency rather variable between specimens; setae absent medially. Preopercular pores convex, each 3–4 µm wide, present as follows: CA1 with 0; CA2 0–11, CA3 0–31 and CA4 with 10–40 pores (none present associated with CA5, when present). Other dorsal pores of two types: (i) a small pore about 3 µm wide and (ii) a minute pore about 1 µm wide, both pore types appearing as pale spots in the sclerotised derm, delineating a polygonal pattern, but type (ii) also sparsely present just dorsad to margin. Anal plates elongate, together narrowly quadrate, each plate with anterior margin generally shorter than posterior margin, 3 minute setae near posterior apex plus 1–3 small pores medially; length of plates 260–320 µm, combined width 200–205 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. Margin with shallow corrugations, each with short, shallow radial lines or ridges, with mostly 3 or 4 corrugations between 2 setae. Marginal setae broadly fan-shaped, each fan wider than long, about 38–45 µm wide, 25–35 µm long; with about 110–140 setae anteriorly on head between anterior stigmatic clefts, each side with 55– 65 between stigmatic clefts and 11 5–140 on abdomen. Stigmatic clefts quite deep, each with a narrow entrance, a sclerotised inner margin and with 3–7 elongate, blunt stigmatic spines [all type specimens with more than 3 apart from lectotype, which has 3 in 3 clefts and 6 in the fourth; all other specimens from Asia with only 3 stigmatic spines per cleft, but Australian specimens with 4–7]; when stigmatic spines numbering more than 3 per cleft, anteriormost setae often longest; length of each stigmatic spine 23–60 µm. Eyespots each in a socket 90–100 µm across at most, each lens about 25 µm in diameter.
Venter. Derm membranous; marginal band about 160–170 µm wide. Multilocular disc-pores frequent on either side of genital opening and on preceding two segments only, each side with 25–44 on abdominal segment VII, 30– 55 on segment VI and 22–27 on segment V. Spiracular disc-pores in a narrow band mostly 1 pore wide between margin and each spiracle, with 26–40 pores in each band, but posterior band tending to have fewer because pores absent in middle part of band. Ventral microducts minute, present in dense group just posterior to and on either side of labium; probably present but very sparse elsewhere. Ventral setae: with 1 or 2 pairs of setae between antennae; pairs of long pregenital setae on segments VII–V (that on VII 105–135 µm long); small setae frequent medially just anterior to vulva on abdominal segment VII; submarginal setae sparse and extremely short; a group of setae sometimes present on each side of anal cleft near anal plates; otherwise ventral setae short and very sparse. Antennae reduced, each with 3 or 4 segments (segmental divisions between segments IV–VI absent); total length 115–125 µm. Clypeolabral shield 125–145 µm long. Spiracles: width of each peritreme 40–48 µm. Legs present but reduced to very small stubs showing no segmentation.
Comments. Adult female D. expansum appear to be rather variable, particularly in the number of spines in each stigmatic cleft. The type series from Sri Lanka and the specimens from Australia usually have 4 or more spines per cleft, whereas almost all other specimens here considered to be D. expansum have only 3 per cleft. As the lectotype specimen has 3 spines in three of the clefts but 6 in the fourth, it is here considered that this variation does not indicate a specific difference. The main characteristic diagnosing adult female D. expansum is the presence of unsegmented leg stubs. These could be found on all the specimens with a venter. Other significant characteristics are: (i) preopercular pores absent from anteriormost clear areas (CA1 and CA2; rarely with a few present associated with CA2) and clearly most abundant associated with the posterior two clear areas (CA3 and CA4)); (ii) stigmatic spines all rather long and narrow, often rather bent; (iii) dorsal setae parallel sided or capitate, generally with some setae present submedially; (iv) marginal setae fan-shaped and most distinctly wider than long; (v) multilocular disc-pores present on segment V, and (vi) marginal ornamentation in the form of shallow castellations with short radial lines. As many of these character-states are found on other species (e.g., D. metallicum , D. quadratum and D. rotundum ), specimens with only 3 stigmatic spines in each cleft and lacking a venter cannot be identified to species because the presence of unsegmented leg stubs is unknown.
Comparison of the specimens from Australia labelled Lecanium expansum javanicum with those of the type series of Paralecanium expansum javanicum (described below) clearly shows that the Australian material is different. However, the four Australian specimens do appear to be extremely similar to P. expansum expansum , as previously suggested by Froggatt (1915). Froggatt recorded Lecanium expansum Green on the leaves of “The Moreton Bay Fig ( Ficus macrophylla ), in the public gardens at Maryborough, Queensland ”. The present material is also off fig from Queensland (though not from Moreton Bay) but the Australian specimens differ from the Sri Lankan specimens in their dermal sculpturing. All of the specimens of D. expansum from Sri Lanka have minute clear spots on the dorsum throughout, whereas these are absent from the Australian and Indian specimens, which have diffuse polygonal markings instead. The presence of leg stubs on both the Indian and Australian specimens strongly suggests that these are also P. expansum . Despite the differences in dorsal ornamentation, it is here considered that both the Indian specimens and those from Australia refer to D. expansum , with the dorsal polygonal markings possibly due to differences in mounting techniques.
Based on the records above, D. expansum has been recorded from Australia, China ( Hong Kong), India, Papua New Guinea, Sri Lanka, Indonesia (Sulawesi Utara), Thailand and Vietnam.
Host-plants. Annona reticulata , Polyalthia pendula ( Annonaceae ); Hemicyclia sp. ( Euphorbiaceae ); Dalbergia championii ( Fabaceae ); Litsea zeylanica ( Lauraceae ); Ficus sp, Ficus microcarpa , Ficus retusa ( Moraceae ); Gymnacranthera sp., Myristica fragrans ( Myristicaceae );? Bruguiera sp. ( Rhizophoraceae ); Dendrotrophe frutescens ( Santalaceae ); Mimusops sp. ( Sapotaceae ); Viscum orientale ( Viscaceae ). Unconfirmed host plants: Calophyllum sp. ( Calophyllaceae ); Litsea glutinosa , Machilus thunbergii ( Lauraceae ); Morella sp., Myrica rubra ( Myricaceae ); Rhizophora sp. ( Rhizophoraceae ), and Zingerberaceae.
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