Isca purpurea Gillies, 1951

Figs 6 B, 8, 9, 10, 11, 12

Isca purpurea Gillies, 1951: 21–130, figs 15–22 (male, female). Type: male, from China (Hong Kong) and India (Mirik).

Isca purpurea: Peters and Edmunds 1970: 159–240, figs 71, 106, 330, 350–357 (nymph, male).

Material examined.

• 55 nymphs, Chebaling Mountain, Shaoguan City, Guangdong Province, China, 460 m a. s. l., 24.701644°N, 114.190687°E, 2024-IV-2-14, Dewen Gong, Xuhongyi Zheng leg. • 10 male imagoes, 3 female subimagoes, 3 nymphs, Laipoli, Jinan District, Fuzhou City, Fujian Province, China, 390 m a. s. l., 26.251947°N, 119.283899°E, 2024-IV-25, Xuhongyi Zheng leg. • 5 nymphs, Jiulian Mountain, Ganzhou City, Jiangxi Province, China, 24.539800°N, 114.467900°E, 2020-IX-14, Zhengxing MA leg.

Description.

Nymph (in alcohol, first formal description): Body length 4.0– 4.5 mm (Fig. 8 A, B).

General coloration brownish, thorax light brown, abdomen brownish, without any specific pattern, ventral surface much lighter. Wingpad dark brown, legs uniformly yellowish (Fig. 8 A, B).

Head: prognathous (Fig. 8 A, B). Labrum ca. 1.8 times wider than long, anterior margin concaved in the middle, lateral-anterior angle rounded, lateral-posterior margin shrunken inward; dorsal side with two rows of setae anteriorly, anterior row denser than posterior row but length of them subequal (Fig. 9 A).

Mandible with rounded outer margin, with 14 setae in the middle; outer incisor of left mandible with 3 apical teeth, inner incisor with 3 teeth, prostheca with a spur and a tuft of spines; outer incisor of right mandible with 3 teeth, inner incisor with 2 teeth and a denticle aside, prostheca with a relatively small spur and a tuft of spines, 4 long setae under the molar (Fig. 9 B).

Hypopharynx: superlinguae with concave lateral margins, apex with setal tufts, lateral angles rounded (Fig. 9 C).

Maxilla covered with dense crown of setae, galea-lacinia with row of setae, margin of cardo with 5 long setae; maxillary palp 3 - segmented, length ratio of 3 segments from I to III = 1.6: 1.0: 1.2, outer margin of segment I with 5 setae, segment II with a seta on the tip, segment III with 2 setae, tip of segment III with tuft of relatively short setae (Fig. 9 D).

Labium like other Isca species, the ratio of 3 segments of labial palp from I to III = 1.3: 0.9: 1.0 (Fig. 9 E).

Thorax: Setae on outer margin of femur strong, relatively longer than that on inner margin; inner margin of tibiae and tarsi with stout setae; outer margin of tibiae and tarsi with hair-like setae, those on tibia of hindleg with extra stout setae (Fig. 8 C – E). Claw with 11 denticles 4 on inner side small, 1 on outer side biggest (Fig. 8 F). Ratio of femora: tibiae: tarsi of forelegs = 2.0: 1.8: 1.0, that of midlegs is 2.3: 1.9: 1.0, and hindlegs = 2.5: 2.2: 1.0 (Fig. 8 C – E).

Abdomen: posterior surface of each tergite with contiguous acute spines, posterolateral projection on segment IX only (Fig. 8 A, B). Gills present on segments II to VII of ventral abdomen (Fig. 8 B). Gills II to VI similar morphologically, consisted of two slender and unbranched lamella, gill VII with single slender lamella (Fig. 8 G, H).

Male imago (in alcohol; also see Gillies 1951 and Peters and Edmunds 1970):

Body length 4.5 mm, generally brownish (Fig. 10). Head: Compound eyes contiguous basally, upper part separated with dark stripes around facets (Fig. 11 A).

Legs generally dark brown, mid part of femora slightly lighter than both ends, tarsus of foreleg brownish from base to tip (Fig. 11 C). Ratio of femur: tibia: tarsus of foreleg = 1.0: 3.1: 3.1, those of midleg and hind leg = 2.9: 2.2: 1.0 and 3.2: 2.5: 1.0, ratio of foretarsal segments from I to V = 1.0: 13.7: 12.5: 8.0: 3.0 (Fig. 11 C – E). Claw dissimilar, one hooked and acute, one blunt (Fig. 11 F).

Wing brown, transparent; veins clear, posterior margin with cilia, vein MA forked slightly more than 1 / 2 of distance from base to margin (Fig. 11 B).

Abdomen: tergites of both dorsal and ventral view dark brown; tergite IX with posterolateral projection (Fig. 10). Genitalia: forceps brownish, segment I longest, midpart slightly protuberant inward; segment II slightly longer than III. Penes brownish; broad at base, gradually narrowing to tip; base separated; tips sharp, bend inward; length of penes about 2 / 5 of forceps (Fig. 11 G).

Female (in alcohol): Body length 4.2 mm, terminal filaments brown with spine-like setae. Coloration like male, apex of sternum IX deeply concave (Fig. 12).

Egg.

Egg oval, length about 100 μm, width about 50 μm, surface covered with subequal small protuberances (Fig. 6 B).

Biology.

Like I. acutata, nymphs of I. purpurea were found under stones with coarse surfaces in slow flowing mountain stream; the stream was about 2 m wide with good shade (Fig. 13).

Diagnosis.

The nymph of I. purpurea can be distinguished from other Isca species by the following characters: abdominal terga brown, and abdominal sterna light brown. The male imago of I. purpurea can be distinguished by vein MA forked slightly more than 1 / 2 of the distance from base to margin (Fig. 11 B); cilia present on the posterior margin of the wings (Fig. 11 B); abdominal terga and sterna dark brown (Fig. 10); forceps and penes brown (Fig. 11 G); and penes separated widely at base, tip hook-like, curved inward (Fig. 11 G).

Distribution.

China (Hong Kong, Guangdong, Fujian, Jiangxi); India.