A new species of spider (Araneae, Linyphiidae, Islandiana) from a southern Indiana cave

The genus Islandiana (Araneae, Linyphiidae) was erected by Braendegaard in 1932 and is comprised of 14 species, most of which are native to North America. Herein we add a 15th species, Islandiana lewisi sp. n., from southern Indiana, USA. This species resembles both I. flavoides Ivie, 1965 and I. cavealis Ivie, 1965, the latter of which is geographically-close.


Introduction
The linyphiid genus, Islandiana Braendegaard, 1932possesses 14 species (World Spider Catalog 2017), most of which are in the United States.However, two species in the genus, I. falsifica Keyserling, 1886and I. cristata Eskov, 1987, have Holarctic distributions and another, I. princeps Braendegaard, 1932, can be found in North America as well as Greenland and Iceland.The remaining species, 11 out of the 14, are restricted to the US and Canada (World Spider Catalog 2017).Most of the species in Islandiana may be found under rocks near the ground in forests, fields, mountains, beaches, and a variety of other habitats in their known range (Ivie 1965).Four species are known only from caves in the US (Ivie 1965).The genus consisted of only two species, I. falsifica and I. princeps, upon its creation by Braendegaard (1932), but had two species added to it by Kaston (1948;I. flaveola Banks, 1892 andI. longisetosa Emerton, 1882).A revision of the genus was conducted by Ivie (1965) that added nine new species.A single species from Russia, Alaska, and Canada was later added by Eskov (1987).
A re-examination of new distribution records listed for the state of Indiana by Milne et al. (2016) revealed a misidentification of "I.cavealis."These specimens -collected from Stygian River Cave in southern Indiana were found not to be I. cavealis, but an undescribed species within the same genus.Herein we describe this species.

Methods
All measurements are in millimeters.Measurements were taken electronically using a Leica M165C stereoscope, Leica DMC2900 attached digital camera, and associated Leica Application Suite software (LAS Ver. 4.9.0 [Build: 129], Leica Microsystems, Switzerland) at the University of Indianapolis.Photographs were taken with specimens placed in glass dishes containing white sand and ethanol.Carapace width was measured at the widest part of the carapace.Specimens were prepared for SEM photography by dehydration using ethanol solutions that graduated from 70% to 100% over 5-minute intervals.Specimens were then placed in Hexamethyldisilazane (HMDS; 99+%; Alfa Aesar, Heysham, England) for 5 minutes before being removed and placed on filter paper to dry for 5 minutes.Specimens were then mounted on SEM stubs using 12 mm Pelco Tabs (TED PELLA, Inc. -carbon conductive tabs), sputter coated in gold (Cressington Scientific Instruments, Model No. 108) and photographed using a JEOL JCM-6000 NeoScope benchtop scanning electron microscope.The holotype male and paratypes of females and males were deposited at The Field Museum of Natural History (FMNH) in Chicago, IL.Islandiana cavealis, I. flavoides, and I. speophila were examined on loan from The American Museum of Natural History.Type-specimen.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."Description.Male.(N = 2) Carapace 0.88-0.94long, 0.69-0.75wide.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).
Distribution.Known only from the type locality.
Habitat.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.