Discochiton vacuum (Morrison)

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: 149-150

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

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Discochiton vacuum (Morrison)


Second-instar male of Discochiton vacuum (Morrison)  

( Fig. 63 View FIGURE 63 )

Material examined. SINGAPORE, intercepted at San Juan, U.S.A. (5987), on leaf of orchid, 22.ix.22, G. Vasquez ( USNM): 1/1 second-instar male (mainly g).

Slide-mounted specimen. Body broadly oval. Length 2.9 mm, width 2.1 mm.

Dorsum. Derm membranous, without areolations. Marginal radial lines, stigmatic bands and clear areas absent. Dorsal setae absent. Dorsal pores present, each about 1.0–1.5 µm wide, sparse, apparently randomly distributed over dorsum. Dorsal tubular ducts of 2 sizes: (i) large ducts present submarginally, each with outer ductule about 65–80 µm long, mainly in groups of 3 with their dermal openings very close together, with 12 groups between clefts anteriorly (total 28 ducts); each side with 3 or 4 groups of 3 between clefts (total 9–12), and 5 groups on abdomen (total 13–15 on each side); and (ii) much smaller ducts, each with outer ductule about 25 µm long, as follows: submedial lines extending from each anal plate to about dorsad to each scape, each line with 23–28 ducts, plus lines extending radially to margin, each with 2–4 ducts, with possibly 1 radial line on head, 1 extending towards each stigmatic cleft and 4 lines on each side of abdomen; also with 3 transverse lines medially, each with 2–4 ducts. Anal plates damaged and mainly missing, but each perhaps with a sharp bend in outer margin and slightly longer than wide; length of plates 135? µm, combined width about 100? µm. Anal fold with 1 pair of small setae along anterior margin, each lateral margin with 1 seta anteriorly and another posteriorly. Anal ring with 3 pairs of setae.

Margin. Marginal ornamentation absent. Marginal setae finely spinose, each mostly slightly bent near apex with either a blunt or capitate apex, 7–9 µm long; with about 38 setae between anterior stigmatic clefts, each side with 13 or 14 between clefts and 30–34 along abdominal margin. Stigmatic clefts narrow but quite shallow, each with a sclerotised inner margin and 3 stigmatic spines; all median spines missing, lateral spines all short, blunt and parallel-sided, length of each lateral spine 20–25 µm. Eyespots each more or less round, located away from margin on dorsum, diameter of each lens about 20 µm.

Venter. Derm membranous. Multilocular disc-pores absent. Spiracular disc-pores small, each 3–4 µm wide; number of loculi hard to determine but thought to be 5–7; present in a narrow band between margin and each spiracle, with 7–15 pores in each band (1 anterior band damaged). Ventral microducts small, most obvious in a group near labium but also present sparsely elsewhere. Ventral setae: with 2 pairs of interantennal setae; 1 pair of long setae on abdominal segment VII, plus pairs of shorter setae medially on segments V and VI; with 1 small seta associated with each meso- and metacoxa and with a longer seta near each procoxa; a line of 7 very short submedial setae present between anal area and each spiracle; submarginal setae sparse. Antennae each short and 7 segmented; total length 95–100 µm; segments V and VI each without a setose seta. Clypeolabral shield about 105 µm long. Spiracles: width of each peritreme 21–27 µm. Legs very reduced but with all segments visible; length of each hind leg about 70 µm; all digitules short, parallel-sided and blunt; claw without a denticle. Setal distribution: coxa 3; trochanter 0; femur 1; tibia 0 or 1 and tarsus 3.

Comments. The second-instar male of D. vacuum   is very different from that of D. martini   described above and of D. malainum   (see Table 3). This specimen is believed to be D. vacuum   as it was collected on the same plant species as an adult female and was intercepted at the same time. For a comparison with the second-instar males of Paralecanium   , see under the general discussion on immature stages on p. 156 below.


Smithsonian Institution, National Museum of Natural History