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 : 143-145

First-instar nymph of Discochiton expansum Green

( Fig. 60 )

Material examined. CHINA, Hong Kong, Braemar Hill Road, Choi Sai Wou Park, on Machilus / Litsea sp. 1.xii.2003, S.K. Lau & J.H. Martin #7887A ( BMNH): 1/15 first-instar nymphs (g).

Note. The description is based on a range of specimens.

Slide-mounted specimen. Body oval. Length 495–525 µm, width 275–285 µm.

Dorsum. Derm membranous. Dorsal setae absent. Dorsal simple pores not detected. A pair of trilocular pores present near margin anteriorly on head. Dorsal microducts present, each side with a submarginal line of 11 microducts; and a submedial line of 6 microducts with 1 duct head, 1 on each thoracic segment and 3 on abdomen. Anal plates each with 2 short setae on inner margin, another short seta on posterolateral margin and a long apical seta, 100–200 µm long; length of plates 60–63 µm, combined width 58–60 µm. Anal fold with 1 pair of small setae along anterior margin, each lateral margin with 1 seta posteriorly. Anal ring with 3 pairs of setae.

Margin. Marginal ornamentation absent. Marginal setae finely spinose and curved, each 7–8 µm long; with about 12 setae between anterior stigmatic clefts, each side with 1 between stigmatic clefts, and 8 along abdominal margin. Stigmatic clefts quite broad and deep, each with a sclerotised inner margin and 3 blunt, parallel-sided stigmatic spines, median spine much the longest, each median spine 23–25 µm long, each lateral spine very narrow, 7–8 µm long, arising much nearer to margin. Eyespots located on margin on dorsum, each about 11–12 µm wide.

Venter. Derm membranous. Multilocular disc-pores absent. Spiracular disc-pores small, each with mostly 4 or 5 loculi, present in a narrow band between margin and each spiracle, with 4 pores in each band. Ventral microducts very small, only detected submarginally on head, between pro- and mesocoxae and 1 laterad to metacoxae. Ventral setae: with 1 pair of interantennal setae; 1 pair of long setae on abdominal segment VII, plus pairs of shorter setae medially on segments V and VI; 1 fairly long seta associated with each mesocoxa; a line of 7 short submedial setae present between anal area and each spiracle; submarginal setae few, with 1 on each side between stigmatic clefts. Antennae each 6 segmented; total length 178–186 µm; segments IV and V each without a setose seta. Clypeolabral shield 75 µm long. Spiracles: width of each peritreme 8 µm. Legs well developed; dimensions of hind leg (µm): coxa 43–48, trochanter + femur 71–73, tibia 40–42 (with 2 distinct spinules), tarsus 43–45; claw about 8–10; prothoracic legs each with 2 tarsal digitules, each with a capitate apex, 1 slightly narrower than other; meso- and metathoracic legs each with 2 digitules, offset, 1 much thicker than other, each subequal in length to claw digitules; claw digitules dissimilar, with one broader than other; claw with a shallow denticle. Setal distribution: coxa 5; trochanter 1, quite long; femur 1; tibia 0 and tarsus 3.

Comments. There appears to be very little variation in these data between species. The nymphs of D. quadratum were very young (the coxae had yet to attain full length) whilst that of D. martini was probably fully grown.

For a comparison with first-instar nymphs of other Paralecaniini, see the main discussion of immature stages below on p. 156.

Figures

FIGURE 60. Discochiton expansum (Green), first-instar nymph.