Family STYLONISCIDAE Vandel, 1952

Styloniscus commensalis

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Family STYLONISCIDAE Vandel, 1952

Introduction

Members of Styloniscus Dana and Notoniscus Chilton typically inhabit litter and rotting wood in wet forests. Styloniscus also occurs in damp places in more open habitats (Green 1971) and is present in caves where both epigean and troglobitic species have been collected. One unnamed species has been found associated with ants. The family encircles the Southern Hemisphere with some remote islands included in its distribution. North of the equator it is less widespread. Two species of Styloniscus have been introduced to Britain.

Styloniscidae Vandel, 1952, is a replacement name for Patagoniscidae Verhoeff, 1939, and is conserved under ICZN Article 40. Dana (1853) established Styloniscus with two included species, S. magellanicus and S. longistylis. Jackson (1941) selected the latter as the type species and, although this subsequent designation is valid, the choice would create taxonomic havoc if followed. Styloniscus longistylis is now regarded as a member of Olibrinus Budde-Lund, 1913 (Olibrinidae) (Taiti & Ferrara 1991). Vandel's (1952) later designation of S. magellanicus as type species can not replace that of Jackson but, for practical reasons, this species rather than S. longistylis has been regarded as 'typical' (Green 1961). An application to the International Commission on Zoological Nomenclature (Lehtinen et al. 1994) to replace Jackson's type species with S. magellanicus, so as to reflect modern usage of the genus name, has not been acted on.

In spite of this, the genus is understood clearly and now includes 40 named species and others to be established. Modern authors follow the definition of Vandel (1952) who contrasted it with Trichoniscus.

Diagnosis

Animal does not conglobate. Head with supra-antennal line present, frontal line absent. Eye usually composed of 3 ommatidia, but may be reduced or absent. Antenna 2 flagellum with 3–10 articles in Australasian species. Mandible with molar process. Dactylar organ present on each pereopod. Male with single penis containing 2 ducts which join to lead to 1 median aperture. Pleopods 1 and 2 of male modified as copulatory structures. Pleopod 1 of male with protopod very large, operated by conspicuous muscles from sternite 1. Without pleopodal lungs. Telson trapezoidal.