Discochiton trifasciatum (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: 69-73

publication ID

http://doi.org/ 10.11646/zootaxa.4443.1.1

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scientific name

Discochiton trifasciatum (Green)

comb. n.

Discochiton trifasciatum (Green)   comb. n.

( Figs 26 View FIGURE 26 , 27 View FIGURE 27 and 28 View FIGURE 28 )

Lecanium trifasciatum Green, 1922   , 1024. Type data: SRI LANKA: Batticaloa, on Hemicyclea [= Hemicyclia   ]. Syntypes, female. Type depository: BMNH, London, England, U.K.

Paralecanium trifasciatum   ; Green, 1937, 307. Change of combination.

Material examined. Lectotype f (here designated): SRI LANKA (as Ceylon): top labels: TYPE in red in round label + Lectotype on narrow label; bottom label: Lecanium   / ( Paralecanium   ) / trifasciatum   / Green / from?Hemicyclea / Batticaloa / Ceylon May 0 6 ( BMNH): 1/1adf (g, a young adult; on envelope: coll. E.E.G.).

Other material. MALAYSIA, Kuala Lumpur, on Michelia   sp., 1.i.1943, R. Takahashi (BMNH): 1/10adff (under two cover slips, all mature and almost all with a clear glassy test covering all of dorsum; f-p; plus 1/1 fairly young adf (fg). Both slides labelled [ Paralecanium trifasciatum   micheliae] Takahashi, type, but no evidence found that this was ever described so this is considered to be a manuscript name.

INDONESIA, Java, Buitengor, on Piper nigrum   , no date, A. Zimmermann, #78 (BMNH): 2/4adff (f-g, one specimen missing venter; labelled [ Paralecanium   zimmermanni] Green; this is clearly a manuscript name).

Note. The main description is based on the very young lectotype specimen; details for mature specimens from Malaysia and Java given in [...] brackets where different.  

Unmounted material. “Adult female flat, broadly rounded, subround, the margin indented on the frontal and stigmatic areas. Colour pale translucent green, with three broad, reddish brown transverse bands across the dorsum.” ( Green, 1922: 1024).

Slide-mounted adult female. Body small and almost round. Length 2.0 [4–5] mm, width 1.9 [3–5.0] mm.

Dorsum. Derm of young specimen unsclerotised [older specimens with derm partially to completely sclerotised; older Malaysian specimens with a less sclerotised border along margin; submarginally with elongate areolations (Java) or small pale spots (Malaysian), both lots of specimens with areolations becoming rounder, sparser and less clear submedially and medially; also with a band of more elongate areolations around anal plates; rest of derm apparently without minute pale spots]. Marginal radial lines obscure but positions indicated by distribution of pores and setae; with 13 radial lines of setae on head between anterior stigmatic clefts, each side with 4 or 5 between stigmatic clefts and 12 or 13 along abdominal margin; stigmatic rays present (but not visible on unsclerotised lectotype specimen). Abdominal clear areas not apparent (perhaps due to membranous derm of young individual) [present]. Dorsal setae each stoutly setose, narrowing to a blunt apex but sometimes appearing more pointed [almost capitate ( Malaysia)], about 8–10 µm long with basal socket about 4–5 µm wide; frequent in a sparse polygonal pattern, pattern becoming less clear medially where setae sparser. Preopercular pores each unevenly round to oval, with a granular surface, unusually large, each 5–8 µm wide; distributed as follows: CA1 with 0, CA2 with 3 or 4 [0 or 1], CA3 with 24–29 [0–22] and CA4 each with 21 or 22 [15–24] pores. Small simple pores, each about 1 µm wide, infrequent, probably situated mainly within lines of setae. Larger dorsal pores not detected [probably present as oval pale areas with a pore medially]. Anal plates elongate, together narrowly quadrate, with posterior margins slightly longer than anterior margins; each plate with 3 or 4 small setae near apex plus 1 or 2 minute pores medially; length of plates 200 [210–230] µm, combined width 145 [155185] µm. Anogenital fold with 4 [2–4] minute setae at each corner of anterior margin, each lateral margin with 1 seta anteriorly.

Margin. Marginal ornamentation: groups of radial finger-like ridges [broader, with 3 or 4 corrugations with fine radial lines between marginal setae]. Marginal setae roundly to broadly fan-shaped; width of each fan about 25–40 [40–45] µm, length 30–35 [40–45] µm; with 100 [104–115] setae anteriorly on head between anterior stigmatic clefts; each side with 44–54 [49–68] between stigmatic clefts and 92–99 [103–120] on abdomen. Stigmatic clefts quite deep, each with a narrow entrance, a sclerotised inner margin and 3 elongate, blunt stigmatic spines; median spines longest, 38–40 [36–50] µm long, laterals 25–30 [21–33] µm. Eyespots obscure [distinct; greatest width of each socket about 60 µm, width of each lens perhaps 20 µm].

Venter. Derm membranous without a submarginal border or dermal fold. Multilocular disc-pores frequent on either side of genital opening and on preceding segment only, each side with 7 [5–9] on abdominal segment VII and 8–10 [9–14] on segment VI. Spiracular disc-pores present in a band 1 [1 or 2] pore wide between margin and each spiracle, with 27–38 [18–37] pores in each anterior band and 22–24 [17–36] in each posterior band (the latter band sometimes without pores in middle part of band). Ventral microducts minute, present in a group just posterior to and on either side of labium, sparse elsewhere, particularly submarginally. Ventral setae: with 1 [1 or 2] pairs of setae between antennae; a long pregenital seta on segment VII (about 50 µm long) [85–115 µm], and shorter pairs in segments VI and V; all abdominal segments with rows of minute setae; small setae also abundant submarginally on either side of anal cleft and more anteriorly, often mirroring lines of setae on dorsum. Antennae reduced, each with 3 segments (segmental divisions between segments III –VI absent or obscure); total length 165–180 [170–215] µm. Clypeolabral shield 106–110 [100–110] µm long. Spiracles: width of each peritreme 36–40 [33–55] µm. Legs well developed; metathoracic leg segment lengths (µm): coxa 105 [100–125]; trochanter + femur 145–150 [140– 170]; tibia 70–75; tarsus 95–105 [tibia + tarsus generally more or less fused and sometimes slightly distorted, 185– 225]; claw 12 [10–12]; metathoracic leg setal distribution: coxa 6 [5 or 6], trochanter 1; femur 1, tibia 0, tarsus 3; tarsal digitules subequal in length to claw digitules, with small capitate apices; claw digitules both broad and subequal [1 narrower than other]; claw probably without a denticle.

Comments. The lectotype specimen is a very young adult (dorsum membranous) whilst those from Java and, more particularly from Malaysia are mature, well sclerotised and very much larger. No significant differences could be detected between these lots of material. Based on these specimens, the diagnostic characters of the adult female of D. trifasciatum   are: (i) legs present and well developed, tibia + tarsus particularly long and sometimes fused; (ii) dorsal setae each stoutly setose, tapering to a blunt apex; (iii) dorsal setae distributed in a reasonably clear polygonal pattern and generally extending medially; (iv) preopercular pores each quite large, with a granulate surface; (v) preopercular pores only associated with CA2–CA4, CA1 without pores; (vi) tibia without setae; (vii) antennae reduced to probably 3 segments (segmentation obscure), and (viii) multilocular disc-pores few and only present on abdominal segments VI and VII.

Only two species of Discochiton   have fully-developed legs, D. trifasciatum   and D. luzonicum   . These two species are very similar but the latter species has preopercular pores associated with CA4 only.

Host-plants.? Hemicyclea sp. ( Euphorbiaceae   ); Michelia   sp. ( Magnoliaceae   ); Piper nigrum   ( Piperaceae   ). Unconfirmed plant host: Drypetes sumatrana   ( Euphorbiaceae   )).


Serengetti Research Institute














Discochiton trifasciatum (Green)

Chris J. Hodgson & Douglas J. Williams 2018

Lecanium trifasciatum

Green 1922