Biol. Inl. Wat. Suppl. 2 (Proc. 1st Symp. BSA), 101–108, K. Tojo, K. Tanida and T. Nozaki (eds.)© 2013 Scientific Research Society of Inland Water Biology

Two polycentropodid caddisflies (Trichoptera, Insecta) collected from
Yonaguni-jima, westernmost Japan
Takao NOZAKI1* and Noriyoshi SHIMURA2
1

Midorigaoka 3-16-15, Ninomiya-machi, Naka-gun, Kanagawa 259-0132, Japan
Daisansanhaimu 106, 2-38-14, Nagatsuta, Midori-ku, Yokohama-shi, Kanagawa 226-0027, Japan.
(*) corresponding author: takao.nozaki@nifty.com

2

Abstract
Two Taiwanese caddisflies, Polycentropus nigrospinus and Polycentropus unicus both described by Hsu and Chen
(1996) were collected from Yonaguni-jima, Japan for the first time, and are transferred into the genera Plectrocnemia
and Polyplectropus, respectively. Males and females of both species are redescribed, and their immature stages are described for the first time.
Key words: Trichoptera, Polycentropodidae, new combination, redescription, adult, immature stage, Taiwan

Introduction
Yonaguni-jima is the westernmost island in Japanand very close to Taiwan (Fig. 1). Shimura (2010)provided a fauna list of Ephemeroptera, Plecoptera
and Trichoptera of this island for the first time, andrecorded 16 caddisfly species including two unidentified

polycentropodids(Plectrocnemia

sp.

and

Polyplectropus sp.). After comparison of these unidentified specimens with Taiwanese material which
was kindly provided by Dr. L. Hsu, Dayeh University,
we recognized that they are the same species as
Polycentropus nigrospinus Hsu and Chen, 1996 andPolycentropus unicus Hsu and Chen, 1996, respectively. Based on characters of their wing venation and

Fig. 1. Location of Yonaguni-jima.

male genitalia, they apparently belong to the genera
Plectrocnemia Stephens and Polyplectropus Ulmer,

genitalia were figured after being cleared in a 10%

respectively. In this paper, we redescribe males andsolution of KOH. Morphological terms mainly follow

females of these two species, and describe the imma-

Arefina et al. (2003) and Morse et al. (2012) for the
adult, and Wiggins (2004) for the larva and pupa. De-

ture stages of them for the first time.

positories of the specimens are abbreviated as follows:

Material and methods

Natural History Museum and Institute, Chiba (CBM);
L. Hsu, Dayeh University, Dacun, Taiwan (LH); andImmature stages were associated with the adultauthors (T. Nozaki (TN), N. Shimura (NS)).

by the metamorphotype method. Male and female101Descriptions

with obtuse angle of about 130°; basal half with tworows of very tiny spines ventrally; apical half withseveral dorsal hair-like spines at base, their number

Plectrocnemia nigrospina (Hsu and Chen, 1996)
Figs. 2, 4, 5

and arrangement variable.
Pupa (Figs. 4E–F). Mandibles slender, curved
mesad, without teeth. Anterior hook plates present on

Polycentropus nigrospinus Hsu and Chen, 1996,
120–121, male, female. New combination.

abdominal segments III to VIII, posterior hook platespresent on segment V. Abdominal gills present
anterolaterally, arrangement variable: one male pupa

Adult. Head and body dark brown, antennae
light brown with dark bands. Forewings dark brownbearing gills on segments II to V, all single and fila-with many small pale yellow spots, 5–6 mm long in

mentous; another male pupa bearing gills on segments

male (n=5), 5–7.5 mm long in female (n=10). Fore-

II to VII, those on segments III to V branched. Analwings with forks I, II, III, IV and V; hind wings withprocesses thick, their round apices with many longforks I, II and V; discoidal cell closed in both wings;
median cell closed in forewing.

setae. Pupal cocoon covering rough dome-shaped
shelter constructed of plant pieces and small rock

Male genitalia (Figs. 2A–H). Sternum IX trape-fragments.

fused with semimembranous segment X. Segment X

Specimens examined. JAPAN: Yonaguni-jima:
1 male, 1 female, Dunan-dagi, 13.iv.2011, N. Shimura

tapering to round apex in lateral aspect. Preanal ap-(TN); 4 larvae, 1 male pupa, ibid., 6–13.iv.2011, N.

pendages broad club-like in lateral aspect.
Mesoventral process of each preanal appendage

Shimura (TN); 4 males, 9 females, Urada,
8–11.iv.2011, N. Shimura (2 males, 2 female: CBM;

strongly sclerotized, each divided into two acute

others: TN); 1 larva, ibid., 7.iv.2011, N. Shimura

branches, upper one longer, both rugose. Inferior ap-(NS); 1 male, Urabu, 27.iii.2009, N. Shimura (TN); 2

pendages large, trapezoidal in lateral aspect, withfemales, ibid., 2–3.iv.2010, N. Shimura (1 female: NS;

mesal plate and ventromesal process; mesal plate with

1 female: TN); 3 larvae, Kubura, 5.iv.2011, N. Shi-short dorsal process bearing two spine-like setae;
ventromesal process slender, digitate, with short se-

mura (NS); 1 male pupa, Mantabaru, 8.iv.2011, N.

zoidal in lateral aspect. Tergum IX semimembranous,

tose lobe midway, round apically and with many tiny

Shimura (NS). TAIWAN: 1male, 1 female, WuchengVill., Yuchi, Nantou Co., 8.ix.2003, L. P. Hsu (LH).

teeth. Subphallic sclerite divided into two short lobes

Distribution. Taiwan, Japan (Yonaguni-jima).

withJapanese name. Taiwan-miyama-iwa-tobikera.

short

setae

apically.

Phallus

with

large

Female genitalia (Figs. 1I–J). Ventral lobes ofsternum VIII leaf-like, tapering to blunt apices in ven-

Remarks. This species has a closed discoidal
cell on each fore- and hind wing and apical forks I, II
and V on each hind wing, and these characters suggest

tral aspect. Tergum IX sclerotized laterally, membra-

that it belongs to the genus Plectrocnemia (Oláh andnous dorsally. Vulval scale protruding posteriorly,

Johanson, 2010). Although Hsu and Chen (1996)

T-shaped in ventral aspect, with heart-shaped dark

originallypigmentation in ventral aspect. Vaginal sclerite dia-

Polycentropus, probably in the broad sense (including

mond-shaped in middle.

Plectrocnemia species), the monophyly of the genus
Plectrocnemia was recently supported by the mor-phallobase, with pair of long paramere spines dorsally.

Larva (Figs. 4A–D, 5A–C). Length of larva up
to 15 mm. Head yellowish brown, with dark muscle

assigned

this

species

to

the

genus

phological study (Chamorro and Holzenthal, 2011).

scars. Pronotum wider than length, yellowish brown,

The male of this species is very similar to that ofwith dark muscle scars. In forelegs, tarsus about half

Plectrocnemia divisa Ohkawa and Ito, 2007 describedas long as tibia, with one black stout setafrom central Honshu, Japan, but they are easily dis-

ventrolaterally; tibia with three black setaeapicoventrally. Abdominal segments without gills.

tinguishable from each other by the shape of themesoventral process of each preanal appendage andAnal legs long; each anal claw slender, curved gently,

the subphallic sclerite. Each branch of the mesoventral102

Fig. 2. Adults of Plectrocnemia nigrospina. A, male wings. Male genitalia (B–H): B, left lateral; C, left mesoventralprocessof left preanal appendage, left lateral; D, right inferior appendage, mesal; E, ibid., ventral; F, subphallic sclerite, ventral; G,
phallus, left lateral; H, ibid., dorsal. Female genitalia (I–J): I, left lateral; J, ventral. Abbreviations: X = segment X; inf. =inferior appendage; m.p. = mesal plate of inferior appendage; m.v.p. = mesoventral process of preanal appendage; p.a. =preanal appendage; para. = paramere; s.IX = sternum IX; t.VIII = tergum VIII; t.IX = tergum IX; v.l. = ventral lobe; v.m.p. =ventromesal process of inferior appendage; v.s. = vulval scale.

103

process is spread in P. nigrospina, but parallel in P.

unpigmented posteriorly. Tergum X rectangular indivisa; and the lobes of the subphallic sclerite of P.
nigrospina are longer than those of P. divisa.

lateral aspect, strongly sclerotized but dorsal partsemimembranous. Vaginal sclerite slender, curved

Plectrocnemia qianshanensis Morse, Zhong and Yang,

outward anteriorly in ventral aspect.

2012 recently described from eastern China (Jiang-xi,
An-hui, Shaan-xi) is also very similar to this species.

Larva (Figs. 4G–H, 5D–F). Length of larva up to
8 mm. Indistinguishable from Polyplectropus malickyi

Although we did not examine any specimens of P.

Nozaki, Katsuma and Hattori, 2010, described byqianshanensis, these species can be distinguishedfrom each other by the shape of the mesoventral pro-

Nozaki et al. (2010, fig. 5). Head and pronotum paleyellow, muscle scars weakly pigmented, often indis-

cess of each preanal appendage and the mesal plate oftinct. In forelegs, tarsus nealy same length as tibia,

each inferior appendage.

with one brown stout seta ventrolaterally; tibia withtwo black setae apicoventrally. Abdominal segments

Polyplectropus unicus (Hsu and Chen, 1996)
Figs. 3, 4, 5

without gills. Anal legs long; each anal claw slender,

Polycentropus unicus Hsu and Chen, 1996, 118–120,

base, their number and arrangement variable. Despite

concave margin doglegged, with obtuse angle of about
130°; apical half with several dorsal hair-like spines atmale, female. New combination.

statement by Nozaki et al (2010, indicating lack ofventral teeth on anal claws of P. malickyi), anal claws
of both P. unicus and P. malickyi each bearing two

Adult. Head and body dark brown, antennae
light brown with dark bands. Forewings dark brownwith many small pale yellow spots, 4.2–5.0 mm longrows of very tinny spines ventrally on basal half.

in male (n=4), 4.5–6.0 mm long in female (n=5).

Pupa (Fig. 4I). Indistinguishable from pupa of P.
malickyi described by Nozaki et al. (2010). Mandibles

Forewings with forks I, II, III, IV and V; hind wings

slender, curved mesad, without teeth. Anterior hookwith forks II and V; discoidal cell closed in forewings,

plates present on abdominal segments III to VIII,

but open in hind wings; median cell closed in fore-

posterior hook plates present on segment V. Ab-

wing.

dominal gills filamentous, present on segments II to
IV (often also on V) anterolaterally, those on segment

Male genitalia (Figs. 3G–E). Sternum IX
subtriangular in lateral aspect. Tergum IX narrow,

III (often also on IV) branched. Anal processes shortprotruding posterodorsally. Segment X sclerotized

and lobate, with many long setae apically. Pupal co-laterally, membranous mesally. Preanal appendages

coon covered with rough dome-shaped shelter con-thumb-like in lateral aspect, with long stout spine-likestructed mainly of small rock fragments.

seta and long fine setae apicomesally. Dorsobasal
process of each preanal appendage slender, strongly

Specimens examined. JAPAN: Yonaguni-jima:
1 female, Dunan-dagi, 24.iii.2009, N. Shimura (TN); 2

sclerotized; basal 2/5 directed anteriorly; distal 3/5

males, 2 females, ibid., 27.iii.2009, N. Shimura (TN);curved backward, with acute apex. Inferior appendag-

3males, 1female, ibid., 31.iii.2010 (NS); 1 pupa, ibid.,

es long, curved caudoventrad in middle in lateral as-

1.iv.2010, N. Shimura (NS); 4 larvae, 1 male & 1 fe-

pect, apices sharp, concaved dorsally, with small ven-male pupae, ibid., 6–13.iv.2011 N. Shimura (2 larvae,

tral lobe basally. Subphallic sclerite subrectangular inventral aspect, with notch apicomesally; with 4 pairs

2 pupae: TN, 2 larvae: NS); 2 males, Tabaru-suien,
23–27.iii.2009, N. Shimura (NS); 1 male, ibid.,of long spine-like setae on posterior margin, all

3.IV.2010, N. Shimura (NS); 1 male pupa, Urada,slightly curved, outermost ones longest. Phallus sim-

4.iv.2010 (NS); 1 larva, ibid., 7.iv.2011, N. Shimuraple, sinuate ventrally in lateral aspect, apex curved(NS); 1 female, ibid., 9.iv.2011, N. Shimura (TN); 1

ventrad.

female, Urabu, 3.iv.2010, N. Shimura (CBM); 1 male,

Female genitalia (Figs. 3H–I). Ventral lobes ofsternum VIII leaf-like, tapering to blunt apices in ven-

ibid., 6.iv.2011, N. Shimura (CBM). TAIWAN: 1
male, Sheishan Farm, Hoping, Taichung Co.,

tral aspect. Vulval scale large in ventral aspect,

17.xii.2003, L. P. Hsu (LH).

104

Fig. 3. Adults of Polyplectropus unicus. A, male wings. Male genitalia (B–G): B. left lateral; C, dorsal; D, ventral; E, right
preanal appendage, mesal; F, subphallic sclerite, ventral; G. phallus, left lateral. Female genitalia (H–I): H, left lateral; I,
ventral. Abbreviations: X = segment X; d.b.p. = dorsobasal process of preanal appendage; inf. = inferior appendage; p.a. =preanal appendage; s.IX = sternum IX; t.VIII = tergum VIII; t.IX = tergum IX; v.l. = ventral lobe; v.s. = vulval scale.

Distribution. Taiwan, Japan (Yonaguni-jima).

from Yonaguni-jima in wing venation and genitalic

Japanese name. Nagatoge-iwa-tobikera.

characters. The illustration of the lateral view of male

Remarks. A male specimen determined as thisspecies by Dr. Hsu is identical to the males collected

genitalia provided by Hsu and Chen (1996, fig. 6) was
mistakenly printed upside down. The wing venation
105Fig. 4. Larvae and pupae. Plectrocnemia nigrospina (A–F). A, larva, head, dorsal; B, larva, pronotum, dorsal, C, larva, rightforeleg, right, lateral; D, larva, right anal claw, right lateral; E, pupa, head, frontal; F, pupa, abdominal segment IX, dorsal.
Polyplectropus unicus (Hsu and Chen, 1996) (G–I). G, larva, right foreleg, right lateral; H, larva, right anal claw, right lateral;I, pupa, abdominal segment IX, dorsal.

and male genitalia redescribed here suggest that thisthe species are easily distinguishable from each otherspecies does not belong to the genus Polycentropus

by the male genitalia. The preanal appendage of P.

sensu lato, but to the genus Polyplectropus sensu lato

unicus is thumb-like in lateral aspect and bears a long

(Oláh and Johanson, 2010; Chamorro and Holzenthal,

stout spine-like seta with long fine setae apicomesally,2011).

but that of P. malickyi is triangular in lateral aspect

This species is very similar to Polyplectropus
malickyi described from central Honshu, Japan, but

and bears only long fine setae there.

106Fig. 5. Anal claws. Plectrocnemia nigrospina (A–C): A, right, right lateral; B, left, ventromesal; C, left , dorsal.
Polyplectropus unicus (D–F): D, right, right lateral; E, left, ventromesal; F, left, dorsal.

Acknowledgements

his specimens. SEM photographs were taken at the
Research and Planning Division of Kanagawa Natural

We express our cordial thanks to Dr. Hsu Li-Peng

Environment Conservation Center.

(Dayeh University, Changhua, Taiwan) for the loan of107

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