New species of tube web spiders of the genus Ariadna from South Australia (Araneae, Segestriidae)

Jessica R Marsh,Barbara C Baehr,Richard V Glatz,Volker W Framenau

doi:10.3897/evolsyst.2.29172

Abstract

Two new species in the tube-web spider genus Ariadna Audouin, 1826 (Segestriidae Simon, 1893) are described from South Australia based on morphological features of both males and females. Ariadnaclavatasp. n. and Ariadnatangarasp. n. are widespread and sympatric on eastern Kangaroo Island, where they are found beneath bark, in borer holes in dead wood, and in short burrows under rocks. They have also been found in south-eastern mainland South Australia and bring the total number of described Australian Ariadna to 13 species. We showcase intraspecific variation in both species based on a significant number of specimens, including substantial size variation in females and variations in patterns of leg spination. For male Ariadna, we also establish the previously unknown functions of apophyses and spines on the metatarsi and tibiae on the first legs, which are used during mating to clasp the female.

Highlights

Tube web spiders (Segestriidae Simon, 1893) are medium-sized, six-eyed spiders with a distinctive body form; unlike most other spiders the pair of third legs when resting is directed forward, not rearward (e.g. Simon 1893a)
We found variation between females of different species to be relatively low, considering the amounts of intra-species variation
The type specimen of A. octospinata was morphologically similar to the type specimen of A. tangara sp. n., with the exception of the structure of the preening comb on the fourth metatarsus, which was significantly longer, relative to the tarsus, in A. octospinata

Summary

Introduction

Tube web spiders (Segestriidae Simon, 1893) are medium-sized, six-eyed spiders with a distinctive body form; unlike most other spiders the pair of third legs when resting is directed forward, not rearward (e.g. Simon 1893a). Due to the lack of external genitalia, it is not always easy to assess the maturity of a female, resulting in descriptions based upon immature specimens This is the case, for example, for the type specimen of the Australian segestriid Gippsicola raleighi Hogg, 1900 (Giroti and Brescovit 2017). It is the first Australian study of this genus in which comparatively large number of male and female specimens were available for each species allowing the assessment of intraspecific variation of potentially diagnostic characters. We explore the functional role of the spines and apophyses on the first leg of males

Materials and methods

Discussion