Discochiton metallicum (Green) Chris J. Hodgson & Douglas J. Williams, 2018

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: 44-48

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

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scientific name

Discochiton metallicum (Green)

comb. n.

Discochiton metallicum (Green)   comb. n.

( Fig. 15 View FIGURE 15 )

Lecanium expansum metallicum Green, 1904a   , 205. Type data: INDONESIA: Java, Bogor (Botanic Gardens), on Myristica fragrans   . Syntypes, female. Type depository: BMNH, London, England, U.K.

Lecanium expansum metallicum   ; Green, 1904b, 377.

Paralecanium expansum metallicum   ; Sanders, 1906, 9. Change of combination.

Paralecanium metallicum   ; Ali, 1971, 38. Change in status.

Paralecanium expansum metallicum   ; Ben-Dov, 1993, 203.

Paralecanium album Takahashi, 1950   , 53. Type data: MALAYSIA: Kuantan, Bukit Cherakah, Dusun Tua, Selangor, on Durio zibethinus   . Syntypes, female. Type depository: BMNH, London, England, U.K. Syn. n.

Paralecanium vacuum   ; Takahashi, 1939, 115. Misidentification for P. album   .

Material examined. Paralecanium metallicum (Green)   : Lectotype f and paralectotype ff (here designated): INDONESIA: top label: TYPE in red on small round label; bottom label: Lecanium   /? expansum Green   / var. metallicum   / from Myristica fragrans   / Java / coll. Zimmermann / No. 38 (BMNH): 1/2adff (p, almost no venter and broken; lectotype middle specimen). See under comments below. MALAYSIA (as Federated States of Malaya): Selangor, on durian, 2nd Sept. 1928, J.R. Weir #75 (USNM): 2/5adff (2 young adff very good, older adff good, complete).

Paralecanium album Takahashi   : Lectotype f and paralectotype ff (here designated): MALAYSIA: top label: Host- / Durian / Lectotype / paralectotype / small round label with Type in red / I.1922; bottom label: Paralecanium   / album   / Takahashi / Dusun / Tua, Selangor, H.C. Abraham / coll (BMNH): 1/3adff (p, all missing all or most of venter; lectotype specimen bottom left, clearly marked). Other type slides: Malaysia: top label: Host- / Durian / I.1922 / small round label with Type in red; bottom label: Paralecanium   / album   / R. Takahashi / Dusun / Tua, / Selangor / H.C. Abraham (BMNH): 1/1 mature adf (missing all of venter + 2 young adff, showing some venter but badly damaged). Malaysia: top label: Host - / — / H.C. Abra- / ham coll; bottom label: Paralecanium   / vacuum   / Morrison sub / album   Tak. / vi.1921 / Bukit / Cherakah, / Selengor [with additional small round label with Type in red] (BMNH): 1/2adff (p, both missing all of venter). Malaysia: top label: vi. 1921 / Bukit / Cherakah, / Selangor; lower label: Paralecanium   / vacuum   / Morrison / subsp. album   / Takah. / H.C. Abraham / coll. (BMNH): 1/4adff (under 2 cover slips), with an additional small label between cover slips, with Type in red; all p, missing all of venter.

Other material. Paralecanium metallicum   : BRUNEI, Kempung Keriam, on Durio zibethinus   , -. i.1974, no coll. (BMNH; #752, CIE A747): 2/2adff (p).

INDONESIA, Bangka Is., on Annona muricata   ], 1935, Dr. J. vd Vecht ( USNM): 1/1adf (young, missing much of venter)   . Sumatra, Pangkalpinang, Isle of Bangha , on Annona muricata   ] leaves, 1935, Dr. J. vd Vecht #1934 ( USNM): 1/1adf (g).  

MALAYSIA, Selangor, Ula Klang, on D. zibethinus   , 10.iii.1971, no coll. (BMNH): 1/1adf (g). Melaka Prov., Tanjong Than, upper leaf surface of unknown plant, 14.iii.2009, J.H. Martin #8409 (BMNH): 5/5adff (fg-g) + 1/16 first-instar nymphs (g). Kuala Lumpur, on M. fragrans   , 3.viii.1929, Ent. Div., (BMNH): 1/3adff (mainly p, 1 with venter). Malaysia (as Fed. Malay States), Kuala Lumpur, on nutmeg [ M. fragrans   ], 15.iii.1923, G.H. Corbett (BMNH; IEB #773): 1/1adf (g). Malaysia (West), Malacca [Melaka], Pulan Gadong, on leaves of D. zibethinus   , no date, Dept. Agric. # 4/85 (BMNH): 2/2adff (p). Tanjung Gadong, on durian leaves, 31.xii.1981, Y. Ibrahim KC38 (BMNH): 1/1adf (g). Kuala Lumpur, on D. zibethinus   , 15.10.1927, Ent. Div. #423 (BMNH): 2/2adff (one f, other p). Kuala Lumpur, on D. zibethinus   , 5.v.1924, G.H. Corbett (BMNH): 3/4adff (all young ads) + 1 second/thirdinstar female. Seremban, on D. zibethinus   , 25.xi.1924, G.H. Corbett (BMNH): 3/6adff (g) + 1 third-instar female (g). Malaysia (as Fed. Malay States), Selangor, on durian, 2. Ix.1928, J.R. Weir (USNM): 2/5 (g). Ulu Klang, on D. zibethinus   , 10.iii.1971, no coll. (BMNH): 1/1adf (fg). Penang, Sungei Hill, on M. fragrans   , 21.ii.1955, H.T. Pagden (BMNH): 1/1adf (vp). Bukit Cherakah, Selangor, no host, -. vi.1921, H.C. Abraham (BMNH): 2/9adff (p; 6 mature ads, 3 immature ads, all damaged or missing venter; misidentified as P. vacuum   by Takahashi). Kuala Lumpur, Govt. House, on nutmeg, 3.viii.1929, M. Ritchings, IBE coccid 2152 (BMNH): 2/5adf (fp). Sarawak, no other site data, on durian, no date, C.R. Wallace #2116 (BMNH): 1/2adff (p, no venters).

PHILIPPINES, Palawan, Irawan Forest , on upper leaf surface of a woody plant, 20.i.1988, J.H. Martin #5141 ( BMNH): 1/1adf (no venter).  

SINGAPORE, no location data, on Myristica   sp., no other data (BMNH): 1/1adf (p, dorsum only; labelled Lecanium (Paralecanium) expansum Green var. metallicum   ; TYPE, with note saying “mounted by E.E. Green, 1904”). Also: a similar slide with same handwriting but without additional note (BMNH): 1/1adf (p, dorsum only, split into 2 pieces; see under Comments below). Singapore, on M. fragrans   , no date, ex coll. E.E. Green (USNM): 1/1adf (p). Singapore, Malay Peninsula, no host, March 1907, F. Muir #52 (USNM): 2/2adff (p, no venter). Singapore, no host or date, Kot. coll. #55 (USNM): 1/1adf (p, no venter). Singapore, Sentosa Is., no host, 11.ii.1997, M.R. Wilson (BMNH): 2/4adff (mainly g). Singapore, Botanic Gardens, on M. fragrans   , 6.xi.1964, no coll. (BMNH): 1/1adf (p) + 1 unid. sp. Singapore, Bukit Timah Forest, on leaf of unknown plant, 8.viii.1974, D.H. Murphy (BMNH): 5/6adff (fg-p, all but 1 missing venter).

THAILAND, Saranthani , on Durio zibethinus   , 15.x.1964, no coll. ( BMNH): 3/4adff (mainly vp).  

Note. The following description is based on specimens listed under material examined for P. metallicum   , with some details taken from other specimens, particularly those from Malaysia and Singapore, including those of P. album   .

Unmounted material. Dorsal surface metallic and mirror-like (J.H. Martin, notes). “Differs from type [ Lecanium expansum   ] in having a beautiful metallic sheen on dorsum of living insect, disappearing after treatment with potash.” Green, 1904, p. 205).

Slide-mounted adult female. Body almost round. Length 3.25–5.5 mm, width 3.0– 5.5 mm.

Dorsum. Derm membranous on youngest specimens; older specimens becoming sclerotised as follows: mature specimens with a paler marginal band with elongate areolations whose long axes are aligned parallel to margin; submarginal area of more heavily sclerotised derm; submedial and medial areas with a polygonal pattern consisting of more heavily sclerotised, quite broad bands, each band with setae (submedially) and simple pores, and each line with a band of small pale spots on either side; with an unsclerotised paler area in between each line, also with small pale spots; medially, sclerotised pattern consisting of a longitudinal median line with 7–9 lateral branches forming central part; most of submedial and medial derm with a polygonal pattern of small, less sclerotised “cells”. Marginal radial lines not sclerotised but each indicated by presence of setae and simple pores, with 13 lines on head and each side with 5 between stigmatic clefts and 13 on abdomen; stigmatic rays present. With 4 or 5 pairs of abdominal clear areas, and with another associated with each anterior stigmatic rays. Dorsal setae each finely spinose, with a blunt apex but not capitate, 10–13 µm long with a broad basal socket about 6 µm wide, frequent in a sparse polygonal pattern as indicated above; setae becoming slightly sparser submedially and absent medially; each seta usually situated in a small clear area of derm on older specimens. Preopercular pores, each 3 µm wide with a thick margin, small and convex, distributed as follows: CA1–CA3 each with 23–37 pores, CA1 usually with fewest; CA4 without pores. Other dorsal pores: small simple pores, minute and flat, each about 1.5 µm wide, clear on young specimens but appearing as small clear spots in older specimens, sparse throughout in polygonal pattern; other simple pores, each about 1 µm wide, also present in a sparse submarginal ring. Anal plates quite large, together narrowly quadrate, with anterior margin possibly slightly shorter than posterior margin; each plate with 2 minute subapical setae and a longer apical seta, and 3–5 small pores medially; length of plates 310–365 µm, combined width 220–230 µm. Anogenital fold with 3 or 4 minute setae anteriorly on each corner of anterior margin, each lateral margin with 1 seta anteriorly and another posteriorly.

Margin. Margin with corrugations, sometimes as deep as marginal setal sockets, each corrugation with several radial lines or ridges; mostly with 4 or 5 corrugations between 2 setae. Marginal setae broadly fan-shaped and almost circular, width of each fan about 48–50 µm, length 46–48 µm; with 142–175 setae anteriorly on head between anterior stigmatic clefts, and each side with 51–90 between stigmatic clefts and 135–160 on abdomen. Stigmatic clefts quite deep, each with a narrow entrance, a sclerotised inner margin and with usually 3 (rarely up to 7 (Tanjung Tuan, Malaysia, specimens)) stigmatic spines, each spine rather short and blunt with parallel sides, subequal in length, 30–38 µm long, barely reaching narrow part of cleft. Eyespots: diameter of each lens about 33 µm.

Venter. Derm membranous, possibly without a ventral marginal band. Multilocular disc–pores frequent on either side of genital opening and on preceding two segments only, each side with 35–36 on abdominal segment VII, 62–80 on segment VI and 47–52 on segment V. Spiracular disc-pores present in a band often 2 or 3 pores wide between margin and each spiracle, with 31–53 pores in each anterior band and 35–68 in each posterior band, the latter generally without pores in middle of band. Ventral microducts minute, present in a dense group just posterior to and on either side of labium and more sparsely elsewhere. 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 90 –100 µm long); without a group of long setae on either side of 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 extremely short. Antennae reduced, each with 3 segments (segmental divisions between segments III–VI absent); total length 1 30–150 µm. Clypeolabral shield 125–145 µm long. Spiracles: width of each peritreme 60–70 µm. Legs entirely absent.

Comments. Adult female D. metallicum   look superficially very similar to those of P. expansum   but differ in several significant character-states, in particular in having a pattern of broad sclerotised bands on the dorsum, whereas the dorsum of D. expansum   is usually rather uniformly sclerotised. Additional differences are (characterstates for D. expansum   in brackets): (i) legs entirely absent (present as very small stubs); (ii) preopercular pores present associated with anterior three clear areas (most abundant associated with posterior clear areas, absent from most anterior clear areas); (iii) marginal setae almost circular (clearly oval); (iv) stigmatic spines usually fairly short, straight and stoutish (longer, often bent and never stout); and (v) dorsal setae finely spinose, narrowing to a blunt apex (capitate).

García Morales et al. (2016) indicate that the type material of P. expansum metallicum   is in the BMNH collection and is labelled: Lecanium expansum Green   , SRI LANKA (as Ceylon): Punduloya, on leaves of Litzea and Dalbergia   , syntypes, female; type depository: BMNH, London, England, U.K.; and that P. expansum metallicum   was described by Green in 1896. These slides have been seen as part of this study, are not labelled var. metallicum   and all clearly refer to the types of P. expansum expansum Green   (as in Green, 1896, 9), NOT of P. expansum metallicum   ( Green, 1904a, 205). Ben-Dov (1993) gives the type data for P. expansum metallicum   as: INDONESIA, Java (Botanic Gardens), on Myristica fragrans   ( BMNH) as in Green (1904a: 205) and these slides are marked Type. This material was also studied and clearly refers to P. metallicum   . However, there is also another slide in the BMNH labelled “ Lecanium (Paralecanium) expansum Green var. metallicum   : TYPE, Singapore, on Myristica   sp.” but with no other data. This slide has a note saying “mounted by E.E. Green, 1904”. Green (1904a, p. 204) described Lecanium expansum var. metallicum   from material collected in Java. It is therefore clear that the slide labelled ‘Type’ from Singapore is not part of the type series.

Adult female D. metallicum   belong to the group of Discochiton   species that have preopercular pores associated with at least CA1–CA3. It differs from other species in this group in the clear polygonal arrangement of the dorsal sclerotisations and dorsal pale spots. In addition, D. metallicum   has non-setose dorsal setae, quite large anal plates (more than 300 µm long) and broad spiracular disc-pore bands.

Variation. The specimens from Tanjung Tuan, Malaysia, appear to be slightly more uniformly sclerotised than many of the other specimens and the derm is covered in small dermal reticulations (similar to those on some D. expansum   from India). Despite a careful search, no leg stubs could be found perhaps because of the heavy sclerotisation. A note on each slide states “metallic mirror-like dorsal surface” which strongly suggests that these specimens are D. metallicum   .

Host-plants. Myristica fragrans   ( Myristicaceae   ); durian ( Durio zibethinus   , Bombacaceae   ); Annona muricata  

( Annonaceae   ).


Smithsonian Institution, National Museum of Natural History


Serengetti Research Institute


Nottingham City Natural History Museum














Discochiton metallicum (Green)

Chris J. Hodgson & Douglas J. Williams 2018

Lecanium expansum metallicum

Green 1904

Lecanium expansum metallicum

Green 1904

Myristica fragrans

Houtt 1774