Psalidothrips Priesner, 1932

Wang, Jun, Mound, Laurence A. & Tree, Desley J., 2019, Leaf-litter thrips of the genus Psalidothrips (Thysanoptera, Phlaeothripidae) from Australia, with fifteen new species, Zootaxa 4686 (1), pp. 53-73 : 54-55

Psalidothrips Priesner

Psalidothrips Priesner, 1932: 61 . Type-species: P. amens Priesner , by monotypy.

Although extensive morphological diagnoses of this genus are available ( Okajima 1983, 2006; Mound & Walker 1986; Dang et al. 2014), each of these indicates many exceptions to various character states. As a result, these diagnoses are not entirely effective for distinguishing membership of the genus. The only character states shared by all the species listed in Psalidothrips are plesiomorphies, and no single autapomorphy occurs in all of the species allocated to the genus. The genus comprises small and often weakly sclerotised and rather pale species that tend to be flattened dorso-ventrally, and on the head the genae are usually incut just behind the eyes and never bear stout setae. The species from Australia differ in several respects from their congeners in other parts of the world: they appear to be rather less dorso-ventrally compressed, and most available specimens of both sexes are apterae; antennal segment III bears only one or two, instead of three sense cones; the major pair of setae ventrally on the head do not always arise between the tentorial pits; the pronotal anteromarginal and anteroangular setae are not always reduced; the mesopresternum is reduced and commonly absent, and the anterior border of the mesoeusternum sometimes eroded; the fore wings are usually only weakly constricted medially or are parallel sided; the abdominal tergites usually have only one pair of wing-retaining setae, and in macropterae of a few species these setae are small and straight; the sternal discal setae are not always minute; males commonly have tergite IX S2 setae long, instead of short and stout as in typical Phlaeothripinae . The variation in some characters is as follows:

Antennal segments: Species of this genus have 8-segmented antennae and segment VIII varies between species from broadly connected to VII, or scarcely narrower than the apex of VII, through weakly narrowed to the base and shorter than VII, to slender and even with a distinct pedicel. The length of the antennae varies among species, and although segment III is usually longer than wide and longer than segment IV, it is short and wider than long in one species described below.

Antennal sense cones: Species of this genus in the northern hemisphere have 3 sense cones on segment III, and 3 or 4 on segment IV. In contrast, species in Australia generally have 1 or 2 sense cones on III (rarely 0), and usually 2 on IV (sometimes 3 or even 4). In some species, the number is variable among individuals, and even differs between the left and right antennae in some individuals. In one Australian species, antennal segment III bears 0, 0+1, 0 1 +1, or 1+1 sense cones. In one of the species with 3 sense cones on segment III, bipictus described below, one of the paratypes has a fourth small sense cone on this segment.

Sculpture of head and thorax: The dorsal surface of the head is usually smooth, or with weak sculpture only near the posterior margin, but one species has weak to strong net-like reticulation anteromedially on the vertex. The meso and metanota are usually without any sculpture.

Maxillary stylets: Maxillary stylets are usually short, reaching approximately half way to the postocular setae and placed far apart, often V-shaped or U-shaped. But the position of these stylets is commonly disrupted in slidemounted specimens and is thus not a reliable character state for taxonomic decisions.

Pronotal setae: All the species considered here have three pairs of setae elongate (ml, epim, pa), with their apices varying from acute, through bluntly pointed, to weakly capitate. Most species of this genus in other parts of the world have the am and aa setae short, and although this is true of most species of this genus from Australia the am setae are long in three species. In contrast, the aa setae are well-developed in 10 species from Australia, but they are sometimes variable in length such that this character state is difficult to use for species recognition.

Mesopresternum: In the species from Australia considered here the mesopresternum is rarely complete and boat-shaped. Even macropterae of some species have this sclerite partially eroded on the posterior margin, and in apterae it is commonly more extensively or even completely eroded and thus absent. The mesoeusternum anterior margin is similarly variably eroded and incomplete medially, and in some species does not extend laterally.

Pelta: This sclerite, representing abdominal tergite I, is variable in shape amongst the species considered here. It ranges from almost D-shaped with short posterolateral lobes, or widely transverse along the anterior margin of tergite II, to weakly eroded posteromedially, to completely eroded and absent.

Tergite IX setae: In females the major setae S1 and S2 have sharply pointed apices. Males of Psalidothrips are unusual amongst Phlaeothripinae in commonly having setae S2 almost as long as S1 rather than short and stout.

Tube: The tenth abdominal segment is usually shorter than the head. It is short and broad in some species, but more elongate in others. The anal setae are commonly longer than the tube.

Male sternite VIII: One of the species considered here lacks a pore plate on this sternite. Among the other species the pore plate varies from small and almost oval medially, to broadly or narrowly transverse fully across the sternite, or divided into two lateral transverse areas.

Relationships. Within the Phlaeothripinae , Psalidothrips is a member of the Phlaeothrips -lineage ( Mound & Marullo 1996) of fungus-feeding species. It shares with typical members of that lineage the production of species that exhibit dimorphism associated both with sex and also with the presence/absence of wings. Moreover, some species are structurally variable in association with body size. The genus is most closely related to the worldwide genus Hoplothrips in which some species, such as H. pergandei (Hood) from North America, are particularly similar in structure to some species of Psalidothrips . Not all the species of Hoplothrips are closely related to the type species of that genus, H. corticis (de Geer) , but we here restrict the genus to those species which resemble H. corticis in having the maxillary stylets long and close together in the middle of the head. In contrast, the species of Psalidothrips have the maxillary stylets wide apart and low in the head, or else about one third of the head width apart and parallel medially, and with the maxillary palps exceptionally small.

Acknowledgements. A manuscript concerning the Australian members of this genus was first drafted by LAM in 1970, subsequent to visiting Australia in 1967–68 from the British Museum (Natural History) on a research visit sponsored by D.F. Waterhouse, the Chief of CSIRO Entomology. Over subsequent years, further specimens of the genus were collected and slide-mounted. In 2014 Dang Lihong from Beijing, China, whilst working on her PhD, sorted the slides of this genus in ANIC, and drafted a new key to species. Desley Tree, as part of her MSc degree at the University of Queensland, developed and sorted an extensive collection of litter-living thrips. We are grateful to Mark Schutze of Queensland Primary Industries Insect Collection, Brisbane, for arranging the loan to Canberra of all the Psalidothrips slides held at QDPC. The authors are particularly grateful to Alice Wells who collected and processed many litter samples through CSIRO Berlese funnels at Canberra. We also acknowledge research facilities provided by CSIRO, as well as the support to LAM by many CSIRO staff over the past 40 years.