Holotype male and paratype males and females (FMNH, Cat. No. #3260642), in 90% alcohol, with genitalia in separate microvial. Label: “O’Bannon Woods State Park, Stygian River Cave, N38°10', W086°18', (parking lot). Islandiana lewisi.” Specimen collected by M. Milne on 23 October 2016. Type-locality: USA, Indiana: Harrison County, Harrison-Crawford State Forest, Stygian River Cave (N38°10', W86°18'; exact coordinates hidden due to the ecological sensitivity of the type locality).

Islandiana cavealis: USA: Kentucky: Fayette County, Picadome Cave (N37°, W84°) 1 female (AMNH_IZC 00328222); collected by C. Krekeler and J. Rittmann on 1 July 1957. Islandiana speophila: USA: West Virginia: Pendleton County, Trout Cave (N38°, W79°) 1 female (AMNH_IZC 00328223); collected by L.G. Conrad on 4 March 1961. Islandiana flavoides: USA: New York: Orient (N41°, W72°) 1 male (AMNH_IZC 00328224); collected by C.R. Crosby and S.C. Bishop on 21 June 1934.

The species name is a patronym in honor of our friend and colleague Dr Julian J. Lewis, a cave and karst specialist, a leading expert in North American isopod taxonomy, and the original collector of the species.

This species is most similar to I. flavoides Ivie, 1965, a species native to New York, USA and keys out to this species using the key provided by Ivie (1965). However, the males of I. lewisi sp. n. possesses a sinuous embolus not present in I. flavoides (Figs 2A, 3 vs. fig. 27 in Ivie 1965). Moreover, the two enlarged setae on the paracymbium are thinner in I. lewisi sp. n. (Fig. 2B, 3C vs. fig. 27 in Ivie 1965) than in I. flavoides, and the pointed tibial apophysis is rounded in this new species (Fig. 2E vs. fig. 28 in Ivie 1965) compared to I. flavoides. The males and females of I. lewisi sp. n. are also larger (mean of 2 mm for the male and 2.2 mm for the female vs. 1.5 mm male and 1.8 mm female in I. flavoides). The female also differs from I. flavoides females in that the epigynum of the new species has a slightly longer scape, lacks the large circular posterior plate, and possesses ovoid spermathecae compared to the circular spermathecae in I. flavoides (Figs 2C–D, and 4). The female epigynum also resembles that of I. cavealis, but the I. lewisi sp. n. epigynum is more flattened posteriorly and the spermethecae are set more anteriorly than in I. cavealis (Figs 2C–D, and 4 vs. figs 50–51 in Ivie 1965).

Male. (N = 2) Carapace 0.88–0.94 long, 0.69–0.75 wide. Total length 1.90–2.00. Carapace concolorous dusky yellow to tan with a small amount of black surrounding each eye. Five short setae along median line of carapace from fovea leading up to eyes, other setae between posterior median eyes and other eyes leading back to fovea. Abdomen light gray (Fig. 1B). Posterior median eyes about half the size of other eyes. Chelicerae dusky yellow with seven teeth on promargin and five denticles on retromargin. Chelicerae with mastidion low-set near teeth. Stridulatory file present with 14 stridulae. Maxillae concolorous and yellow with labium also dusky yellow. Sternum dusky yellow. Spination is as follows (only surfaces bearing spines listed): femora: I, II, III, IV v0-0-2; patellae: I, II, III, IV d0-0-1; tibiae: I, II, III d1-0-1; IV d1-0-0.

Mature male palp with tibial apophysis rather short and stout (Fig. 2E). Paracymbium notched, curved in a thick “C”-shape, and with two long thin setae and two short thin setae emanating from a deep section of the structure (Figs 2B, 3C). Large tegulum above subtegulum that extends out past subtegulum. Embolus within embolic membrane curves around in full 360° loop near anterior end of cymbium. Suprategular apophysis projects anteriorly within the center of the embolic loop. Ventral and medial processes project anteriorly from embolic division (Fig. 3).

Female. (N = 4) Carapace 0.88–1.00 long, 0.69–0.79 wide. Total length 2.1–2.3. Carapace coloration and setae pattern same as male. Abdomen light yellowish to tan (Fig. 1A). Chelicerae dusky yellow with six teeth on promargin and five denticles on retromargin. Chelicerae lacking mastidion. Stridulatory file present with 16 –18 stridulae. Maxillae, labium, and sternum coloration same as in male. Spination same as in male.

Epigynum similar to I. cavealis. Epigynum protruding ventrally at distal portion; conical shape, posterior sclerite wider distally with flattened triangular shape proximally (Figs 2C–D, 4). Triangular shape of sclerite difficult to see using light microscopy.

Known only from the type locality.

Stygian River Cave is short and consists of a room filled with large, wet, muddy rocks and boulders. Because of the short length of the cave, the biota is likely heavily influenced by low winter humidity. The cave sits at the confluence of the Blue and Ohio rivers and at least part of the cave is regularly underwater when these rivers rise. These specimens were largely found in webs in between the large boulders within the largest room of the cave. The type locality was only visited once and were therefore only collected once, on October 23^rd, 2016.

Figure 1. 

Habitus of Islandiana lewisi sp. n. A female B male.

Figure 2. 

Illustrations of Islandiana lewisi sp. n. structures. A Left palp of male, medial view B Left palp of male, lateral view C Epigynum, ventral view D Epigynum, flipped – dorsal view E Tibial apophysis of left palp of male. E = Embolus; R = radix; SA = suprategular apophysis; ST = subtegulum; T = tegulum; PC = paracymbium; S = spermathecae; PS = posterior sclerite.

Figure 3. 

SEM micrographs of the left palp of Islandiana lewisi sp. n. A Ventral B Medial C Lateral. E = Embolus; ED = Embolic division; EM = Embolic membrane; MP = medial projection of ED; VP = ventral projection of ED; R = radix of ED; SA = suprategular apophysis; ST = subtegulum; T = tegulum; PC = paracymbium.

Figure 4. 

SEM micrographs of the epigynum of Islandiana lewisi sp. n. A Epigynum, ventral view B Epigynum, flipped – dorsal view. PS = posterior sclerite.