Isca purpurea Gillies, 1951

Gong, De-Wen & Zhou, Chang-Fa, 2025, Review of the genus Isca (Ephemeroptera, Leptophlebiidae) from China with a new species and a new species record, ZooKeys 1234, pp. 239-258 : 239-258

publication ID	https://doi.org/10.3897/zookeys.1234.140905
publication LSID	lsid:zoobank.org:pub:70EE2B15-6E8A-4740-897B-BDCE44D02A27
DOI	https://doi.org/10.5281/zenodo.15195801
persistent identifier	https://treatment.plazi.org/id/BADF030C-CCB7-5F0D-ABCE-D2A0225289F9
treatment provided by	ZooKeys by Pensoft
scientific name	Isca purpurea Gillies, 1951
status

Treatment

Isca purpurea Gillies, 1951 View in CoL

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

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

Isca purpurea View in CoL : 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. GoogleMaps • 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. GoogleMaps • 5 nymphs, Jiulian Mountain , Ganzhou City, Jiangxi Province, China, 24.539800°N, 114.467900°E, 2020-IX-14, Zhengxing MA leg. GoogleMaps

Description.

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

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 View Figure 8 ).

Head: prognathous (Fig. 8 A, B View Figure 8 ). 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 View Figure 9 ).

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 View Figure 9 ).

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

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 View Figure 9 ).

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 View Figure 9 ).

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 View Figure 8 ). Claw with 11 denticles 4 on inner side small, 1 on outer side biggest (Fig. 8 F View Figure 8 ). 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 View Figure 8 ).

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

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

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

Legs generally dark brown, mid part of femora slightly lighter than both ends, tarsus of foreleg brownish from base to tip (Fig. 11 C View Figure 11 ). 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 View Figure 11 ). Claw dissimilar, one hooked and acute, one blunt (Fig. 11 F View Figure 11 ).

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 View Figure 11 ).

Abdomen: tergites of both dorsal and ventral view dark brown; tergite IX with posterolateral projection (Fig. 10 View Figure 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 View Figure 11 ).

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 View Figure 12 ).

Egg.

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

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 View Figure 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 View Figure 11 ); cilia present on the posterior margin of the wings (Fig. 11 B View Figure 11 ); abdominal terga and sterna dark brown (Fig. 10 View Figure 10 ); forceps and penes brown (Fig. 11 G View Figure 11 ); and penes separated widely at base, tip hook-like, curved inward (Fig. 11 G View Figure 11 ).