Rhopalopsole mataikan, Stark & Sivec, 2008

Stark, Bill P. & Sivec, Ignac, 2008, Rhopalopsole Mataikan (Plecoptera: Leuctridae), A New Stonefly From Brunei Darussalam, Illiesia 4 (13), pp. 139-142 : 139-141

Rhopalopsole mataikan sp. n.

( Figs. 1-9 )

Material studied. Holotype ♂ from Brunei Darussalam , Sungai Mata Ikan near Kuala Belalong Field Studies Centre , ALS B33-08, 30 June 2008, A.L. Sheldon ( USNM). Paratypes: All from Brunei Darussalam: Sungai Mata Ikan near Kuala Belalong Field Studies Centre, ALS B10-08, 11 June 2008, A.L. Sheldon, 3 ♂ 1 ♀ ( BPS) . Sungai Mata Ikan , Ashton Trail near Kuala Belalong Field Studies Centre, ALS B3-08, 7 June 2008, A.L. Sheldon, 1 ♂ ( USNM) . Same location, ALS B24-08, 22 June 2008, A.L. Sheldon, 1 ♀ ( USNM) . Sungai Esu , upstream Kuala Belalong Field Studies Centre, ALS B31-08, 28 June 2008, A.L. Sheldon, 2 ♂, 2 ♀ ( PMSL) . Sungai Enkabang , ALS B35-08, 2 July 2008, A.L. Sheldon, 3 ♀ ( BPS) .

Adult habitus. General color brown. Head brown with scattered pale spots ( Fig. 1 ). Pronotum with narrow, pale brown bands on either side of median suture bordered by broad pale bands. Wings pale with pale brown veins. Legs pale brown.

Male. Forewing length 4 mm. Lateral spines of tergum 10 forked; arms of fork slightly divergent and upper arm longer than lower ( Figs. 2-3 , 6-7 ). Epiproct slender, curved forward and apically blunt ( Fig. 8 ), cerci with slender apical spine ( Fig. 6 ). Vesicle minute ( Fig. 4 , 9 ).

Female. Forewing length 5 mm. Subgenital plate overlaps basal third of sternum 9; posterior margin and median field of plate darker than adjacent areas

2

( Fig. 5 ). Sternum 9 with a pair of small basal ridges located near subgenital plate apex.

4 5

Larva. Unknown.

Etymology. The species name, based on the type locality, is used as a noun in apposition.

Habitat (based on notes provided by A. L. Sheldon). Adult Rhopalopsole mataikan specimens have been collected along three tributary streams (Sungai Mata Ikan, Sungai Esu, Sungai Enkabang) of Sungai Belalong near the Kuala Belalong Field Studies Centre (04.54822° N, 115.15823° E). Stream channels, located in dense rainforest at 50-70 m asl, are 4-12 m wide during spates, but water levels recede rapidly during times of low rainfall. Reaches of moderate gradient with mixed gravel-cobble-boulder substrate are separated by numerous cascades and waterfalls. Density of Rhopalopsole appears to be low in these streams and considerable effort, requiring 1-2 hours with a beating sheet, was expended in the collection of each adult.

Diagnosis. Males of this species share a forked posterolateral process of tergum 10 with several regional species, including R. sinensis Yang & Yang , R. furcata Yang & Yang , R. baishanzuensis Yang & Li and R. malayana (Banks) ( Jewett 1958; Yang & Yang 1993; Yang & Yang 1994; Yang & Li 2006). It differs from these and other known members of the genus by the very small vesicle on abdominal sternum 9. Females of few species are currently known but the subgenital plate of R. mataikan is distinct from that of R. palawana (Jewett) , R. malayana and R. femina Kawai , the three species known from the Philippine Islands ( Jewett 1958; Kawai 1969).

Figures

Figs. 1-5. Rhopalopsole mataikan adult structures. 1. Head and pronotum, 2. Male, dorsal aspect, 3. Male, lateral aspect, 4. Male, ventral aspect, 5. Female, sterna 8-9.

Figs. 6-9. Scanning electron micrographs of Rhopalopsole mataikan male structures. 6. Terminalia, dorsolateral aspect, 7. Posterolateral process of tergum 10, 8. Epiproct, lateral aspect, 9. Vesicle.