Discochiton martini 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 : 145-148

Second/third-instar female nymph of Discochiton martini Hodgson sp. n.

( Fig. 61 )

Material examined. MALAYSIA, Selangor, Klang Gate Ridge, on unknown host, 27.ii.2014, J.H. Martin #8707 ( BMNH): 2/2 second- or third-instar female (f; both specimens rather poorly cleared).

Slide-mounted specimen. Body broadest across abdomen, more pointed anteriorly and somewhat asymmetrical. Length 1.5–2.3 mm, width 1.25–1.38 mm.

Dorsum. Derm membranous, without areolations. Marginal radial lines, stigmatic bands and clear areas absent. Dorsal setae and dorsal tubular ducts absent, dorsal pores not detected. Anal plates each with a sharp bend in outer margin and slightly longer than wide; each plate with 3 or 4 small setae near apex plus possibly another near inner margin medially on 1 specimen; without small pores; length of plates 124–126 µm, combined width 100–105 µm. Anal fold with 2 pairs 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 with either a slightly fimbriate or capitate apex, each about 10 µm long; with 16–20 setae between anterior stigmatic clefts, each side with 6–10 between clefts and 15–18 along abdominal margin. Stigmatic clefts narrow but quite shallow, each with a sclerotised inner margin and 3 short, blunt, parallel-side stigmatic spines; all median spines missing; each lateral spine 25–27 µm long. Eyespots not detected.

Venter. Derm membranous. Multilocular disc-pores absent. Spiracular disc-pores small, each mostly with 4 or 5 loculi, present in a narrow band between margin and each spiracle, with 5–10 in each band. Ventral microducts very small, distribution uncertain but with a group around labium. 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; a line of 7 short submedial setae present between anal area and each spiracle; and with 1 submarginal seta between stigmatic clefts on each side. Antennae each 3 segmented, apical 4 segments fused; total length 91–95 µm; number of antennal setae reduced. Clypeolabral shield 90–100 µm long. Spiracles: width of each peritreme 21–23 µm. Legs entirely absent.

Comments. Character-states of the other second/third-instar female nymphs of Discochiton seen during this study are shown in Table 2. The basic structure was fairly constant apart from (i) the size of the legs (as small stubs in D. metallicum and as rather well-developed stubs on 1 of 3 specimens of D. sarawakense ), and (ii) the presence of 4 stigmatic spines in some clefts on D. expansum . With regard to whether the specimens studied are secondinstar or third-instar nymphs, these data are not very helpful although there is a suggestion that the specimens of D. expansum and D. sarawakense are larger and may be third-instar nymphs, whereas the remaining (smaller) specimens might all be second-instar nymphs. When these data are compared with those of the second-instar male nymphs of D. martini and D. malainum ( Table 3), the length of the anal plates of D. martini , D. metallicum and D. milleri look very similar to those of second-instar males, also suggesting that these female nymphs may be in their second instar.

There were 3 immature specimens of D. sarawakense . One of these has well-developed leg stubs whereas the other 2 do not; however, both the latter specimens contain adult parasitoids just prior to emergence. Perhaps the presence of the parasitoids changed the growth patterns of the scale insect nymphs so that leg stubs did not develop? The morphological data for all three immature D. sarawakense are very similar (see Table 1) and, as none has dorsal tubular ducts, it seems very likely that all three nymphs are female.

For a comparison with second/third-instar female nymphs of other Paralecaniini, see under the discussion on immature stages below on p. 156.

Second-instar male nymph of Discochiton martini Hodgson sp. n.

( Fig. 62 )

Material examined. MALAYSIA, Selangor, Klang Gate Ridge, on unknown host, 27.ii.2014, J.H. Martin #8707 ( BMNH): 3/17 second-instar male nymphs (mainly fp).

Note. The description is based on five of the best specimens.

Slide-mounted specimen. Body broadly oval. Length 1.18–1.65 µm, width 0.70–0.85 µm.

Dorsum. Derm membranous, without areolations. Marginal radial lines, stigmatic bands and clear areas absent. Dorsal setae absent. Dorsal pores absent apart from a pair of small pores situated just anterolaterally to anal plates. Dorsal tubular ducts of 2 sizes: (i) large ducts, each with outer ductule about 25–35 µm long, in a sparse line submarginally, with 27–29 ducts anteriorly between stigmatic clefts, each side with 6 or 7 between clefts and 11 or 12 on abdomen, and (ii) much smaller ducts, each with outer ductule about 16 µm long, as follows: submedial lines extending from each anal plate to about dorsad to each scape, with 25–30 ducts in each line, plus lines extending radially to margin, each with 2–10 ducts, with 1 radial line on head, 1 extending towards each stigmatic cleft and 4 on each side of abdomen. Anal plates each slightly longer than wide, with a sharp bend in outer margin; each plate with 3 or 4 small setae near apex plus another near inner margin medially; without small pores; length of plates 85– 93 µm, combined width 75–80 µm. Anal fold with a 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 each broadening at apex and slightly fimbriate, 8 µm long; with 17–23 setae between anterior stigmatic clefts, each side with 5–7 between clefts and 12–18 along abdominal margin. Stigmatic clefts narrow but quite shallow, each with a sclerotised inner margin and 3 short, blunt, parallel-sided stigmatic spines, subequal in length, each 16–20 µm. Eyespots not detected.

Venter. Derm membranous. Multilocular disc-pores absent. Spiracular disc-pores small, each mostly with 4 or 5 loculi, present in a narrow band between margin and each spiracle, with 5 or 6 pores in each band. Ventral microducts very small, distribution uncertain. 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; 1 or 2 small setae associated with each coxa; a line of 7 short submedial setae between anal area and each spiracle; submarginal setae sparse. Antennae each 4 segmented, with apical 3 segments fused; total length 125–135 µm; antennal setae reduced, without setose setae on segments IV and V. Clypeolabral shield 80–85 µm long. Spiracles: width of each peritreme 14–15 µm. Legs well developed; dimensions of hind leg (µm): coxa 55–58, trochanter + femur 80–86, tibia 38–41, tarsus 50–55; claw about 7; tarsal digitules offset, subequal in length to claw digitules; claw digitules dissimilar, one clearly broader than other; claw without a denticle. Setal distribution: coxa 4 or 5; trochanter 1, quite long; femur 1; tibia 0 and tarsus 3.

Comments. The above description is very different from that of the second-instar male of D. vacuum described below. For a comparison with other second-instar male nymphs of Discochiton and those of Paralecanium , see under the discussion on immature stages below on p. 156.

Figures

FIGURE 61. Discochiton martini Hodgson, spec. n., second/third-instar female.

FIGURE 62. Discochiton martini Hodgson, spec. n., second-instar male.