(Figs. 5-11)

Material examined. Holotype ♂ and 1 pinned ♀ paratype from Indonesia, East Kalimantan, Long Tua, Bahan River, 3° 10’ N, 115° 47’ E, 440 m, 5-9 April 1994, IIS 940526, B. Hubley, D.C. Darling (MZB). Paratypes: Indonesia: East Kalimantan, Balungan, Kayan Mentarang Nature Reserve, Lalut Birai Research Station, 115° 48’ E, 02° 51’ N, 355 m, 20 February-4 March 1993, IIS 930000, D.C. Darling, 1 ♂ pinned (ROM).

Adult habitus. General color pale brown. Head pale brown but with obscure darker spot between ocelli; lappets and triangular area forward of M-line brown; dusky area and small pale spot define obscure M-line (Fig. 5). Basal two antennal segments pale brown, flagellum dark brown; basal palpal segments pale, apical segments brown. Pronotum brown with slightly darker rugosities. Wing membrane pale amber, veins brown. Femora pale brown, darker on dorsum and at narrow knee band; tibiae and tarsi dark brown.

Male. Forewing length 13 mm. Process of tergum 7 wide and notched; apex lined with a few large sensilla basiconica. Median sclerite of tergum 8 slightly raised, weakly sclerotized and bearing a pair of sensilla basiconica patches. Median field of tergum 9 bearing a boomerang shaped mound, slightly sclerotized at each end, and bearing a few sensilla basiconica. Hemitergal tips turned abruptly inwards, posterolateral margins bearing dense row of short stout bristles and a lateral notch; finger lobes slender, relatively long, directed strongly mesad and curved slightly (Fig. 6). Aedeagal tube poorly sclerotized, plump and sparsely armed with small scale-like spines below and forward of bulb and in a narrow mid-dorsal band; apex of tube armed with a pair of dorsolateral spiny lobes. Everted aedeagal sac with large basoventral spiny lobe, large cushion-like basodorsal spiny lobe and a pair of small lateral spiny lobes at midlength; apex of sac bearing a subapical ring of large spines and, near bases of lateral lobes on dorsal margin, a pair of small patches of ca. 5-6 large spines; much of sac surface covered with fine spinules grading into small spines (Figs. 7- 8).

Female. Forewing length 17 mm. Subgenital plate scarcely produced, posterior margin of sternum 8 almost straight but with two widely separated small projecting points on either side of a slightly scalloped area (Fig. 9). Vagina approximately circular with tiers of internalwrinkles; mostofvaginal areawithbrown lining; spermatheca J-shaped without apical hook (Fig. 10).

Egg. Outline oval, collar short but distinctly stalked; rim of collar flanged and emarginate (Fig. 11). Chorion finely punctate throughout; equatorial region with obscure follicle cell impressions enclosing punctations.

Larva. Unknown.

Etymology. The patronym honors our friend and colleague Professor Dr. Peter Zwick in recognition of his major contributions to the systematics of Neoperla (e.g. Zwick 1980, 1981, 1983, 1988) and in the study of Bornean stoneflies (Zwick 1986).

Diagnosis and Discussion. Neoperla peterzwicki is a member of the “Borneensis Subgroup” of the Montivaga Group of Neoperla. As defined by Zwick (1986), males of the subgroup have a notched or bifurcate process of tergum 7 and the hemiterga have relatively wide bases. The subgroup is presently known only from Borneo and includes seven species or subspecies recognized and described by Zwick (1986). Externally the new species is quite similar to N. harina Navas, N. furcifera Klapálek, N. bilobata Zwick and N. furcata Zwick and less similar to other members of the complex. The aedeagal lobing and armature are suggestive of N. bilobata and N. harina; from the latter, the new species differs in having a much more prominent dorsobasal spiny cushion and in having small spines scattered over most of the sac surface; from the former species it differs in having a larger ventrobasal spiny lobe and in having the largest spines in the apical region arranged in a circumlinear subapical patch rather than along the dorsal margin in a more linear arrangement. The following key is offered for males of the subgroup.