Order THYSANOPTERA

Thysanoptera

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World Thysanpotera

Order THYSANOPTERA

Thrips

Compiler and date details

January 2012 - L..A. Mound, Australian National Insect Collection

August 2010 - Updated by ABRS with data provided by L.A. Mound

July 2008 - Updated by L.A. Mound

1996 - Laurence A. Mound, CSIRO Entomology, Canberra, Australian Capital Territory, Australia

Introduction

Thrips, the insects of the order Thysanoptera, are commonly thought of as flower-living, but this is a misleading summary of their biological diversity. Almost half of the 6000 known species of thrips feed only on fungi, either in leaf litter or on dead branches, a considerable number feed only on green leaf tissues, and a few are predators of other arthropods (Mound & Teulon 1995; Mound 2004a). Although in addition to the 6000 recognised species, another 1500 species-group names are in synonymy (Gaston & Mound 1993; Mound 2008a), and many more species remain undescribed, particularly in tropical countries (Mound & Marullo 1996). Similarly, the total of 738 species recorded here from Australia, together with a further 180 synonyms, possibly represents little more than 50% of the total thrips fauna of this continent.

Background Information
General introductions to thrips structure and biology are provided by Priesner (1964, Egypt), Mound & Heming (1991, Australia), Mound & Marullo (1996, Neotropics), and Hoddle et al. (2008, California); also the computer driven identification systems for pest thrips by Moritz et al. (2001, 2004) contain extensive information. Lewis (1973) provided an outstanding summary of the literature on thrips ecology, and Lewis (1997) edited a multiauthor volume that provides a rich source of information about the biology of pest thrips. A citation index is available to about half of the species described worldwide (Jacot-Guillarmod 1970–1979; Jacot-Guillarmod & Brothers 1986), a complete list and publication details of all described Thysanoptera taxa is available on the web (Mound 2008a), and an overview of the Australian thrips fauna was provided by Mound (2004b).

Classification
Nine extant families in two suborders, the Terebrantia and the Tubulifera, are currently recognised worldwide (Mound et al. 1980; Mound & Morris 2007). This classification contrasts with an essentially phenetic classification recognising many small families and two sub-orders suggested by Bhatti (1994, 2006). Some of the problems associated with such a classification have been indicated by Mound & Marullo (1996). For example, recognition of Xaniothripidae (see Bhatti 1994) for the Australian genus Xaniothrips implies that the species included in that Australian genus comprise a lineage that separated from all other Phlaeothripidae before the radiation of the several hundred other genera in that family. As further discussed by Mound et al. (2008), there is no evidence to support such an evolutionary scenario, and this catalogue retains the more conservative classification.

Five of the nine families of Thysanoptera occur in Australia (Merothripidae, Melanthripidae, Aeolothripidae, Thripidae and Phlaeothripidae), and these are all found in many other parts of the world. In contrast, each of the four families that are not represented in Australia has a restricted distribution. The Uzelothripidae includes a single species from South America that apparently has been introduced to Singapore. The Heterothripidae includes about 70 species in four New World genera, including one species that is uniquely ectoparasitic (Izzo et al. 2002). The Adiheterothripidae includes three small genera, of which one comprises four species from date palms in western Asia and the Mediterranean, and two genera from California. The Fauriellidae includes five species in four genera with a disjunct distribution between South Africa, California and southern Europe, but the phylogenetic significance of these families remains in doubt (Mound et al. 2008).

Previous Studies on Australian Thrips
Between the years 1750 and 1995, the number of thrips species that were described during each 50 year period, and that are now recorded from Australia, was 2, 5, 14, 380 and 172. Most of the earliest names are for European insects introduced to Australia. Of the native fauna, only the Giant Thrips, Idolothrips spectrum (and two of its synonyms), was named before 1900, apparently from specimens collected by Charles Darwin. By 1915 less than 20 Australian species had been described, although in the following ten years more than 100 species were named, and over 160 species in the four years 1926–1929. The final wave of this descriptive activity from the first half of the century appeared as late as 1968 when a manuscript by the Californian, Dudley Moulton (1878–1951), was published posthumously; of the 20 new species described therein, eight are now placed in synonymy, and a further eight allocated to different genera.

Up until the 1960s, studies on the Australian thrips fauna were focussed sharply onto one or other of two separate disciplines, with little interdisciplinary communication. One focus produced a series of outstanding ecological studies on the Plague Thrips, Thrips imaginis (see Andrewartha 1934; Evans 1935). The other produced descriptive taxonomic papers that were largely devoid of biological observations, and were often superficial even by the descriptive standards of the period.

Notorious amongst the group of descriptive taxonomists was A.A. Girault. This author made available 139 species-group names for Australian thrips in a series of privately published, unillustrated, notes that were as remarkable for their outrageously expressed opinions on a wide range of topics as they were for their lack of descriptive detail (Gordh et al. 1979). His slide preparations are exceptionally poor, often with specimens of different species under one cover-glass, and with a surprising number of these cover-glasses broken; also the labels are poorly written and sometimes misleading. He appears to have recognised species largely from colour, rather than from structural details; for example, the specimens he labelled as Thrips lacteicorpus involve three species, Thrips australis, T. imaginis and T. tabaci. Although he was employed at one time to study the biology and control of banana thrips, his descriptive taxonomy is based largely on single specimens with no biological information. Consequently, 75 of the species he described are now placed in synonymy.

Most of the descriptive taxonomy of Australian thrips was published by workers in the Northern Hemisphere with little knowledge of Australian biology. These descriptions were often based on single specimens, sometimes damaged and poorly mounted onto slides (Mound 2008b), with varietal names being erected for particularly large or small individuals. Field observations in Australia by Froggatt (1904) on variation in Idolothrips spectrum, were rejected by the English thrips specialist Bagnall (1916) who would not accept that a single species could vary so much in size and shape. As a result, many of the names from the five major authors of the first half of the century are now placed in synonymy. The number of Australian species-group names erected by each of them, together with the percentage of these names currently recognised as synonyms, is: Girault 139 (54%); Bagnall 63 (33%); Karny 40 (42%); Hood 47 (17%); and Moulton 39 (33%).

Taxonomic studies on thrips within Australia failed to develop, partly due to the technical problems of producing adequate reference collections, but also due to the lack of any useful overview of the subject. Kelly accumulated many notes about thrips, and after his death these were compiled into a book (Kelly & Mayne 1934). Unfortunately, this includes many errors, as does a list of thrips associated with fruit trees in the region of Perth (Newman 1935). In contrast, the keys to common Australian thrips by H. Vevers Steele (1935) (Mrs Andrewartha) proved particularly useful. Her work recognised that certain biological characteristics of thrips (e.g. vagility, variable host-range, intra-specific variation) create problems for species identification. Unfortunately, biological insights from H.G. Andrewartha's ecological studies did not penetrate further into thrips taxonomy for many years.

It was not until the mid 1960s that the concept of inter- and intra-population variation, together with an appreciation that ecology and taxonomy are inter-related aspects of an organism's evolutionary biology, was applied to Australian thrips. Taxonomic studies on the species associated with galls on Acacia trees (Mound 1971a) led to a particularly intensive series of biological studies on this interesting ecological system. These culminated in a major volume that used Acacia thrips as a 'model clade' to examine the evolution of ecological and behavioural diversity (Crespi et al. 2004), and studies on this clade have continued (Bono & Crespi 2006, 2008). Specifically taxonomic studies have focussed either on particular ecosystems, such as leaf litter and dead wood (Mound 1974, 2007; Mound & Minaei 2006), and the gall-inducing suite on the leaves of Geijera parviflora trees (Mound 1971b), or on particular genera (Odontothripiella—Pitkin 1972; Anaphothrips—Pitkin 1978; Thrips—Mound & Masumoto 2005), or higher taxa (Haplothripini—Mound & Minaei 2007; Urothripini—Mound 1972). From these focussed studies, based on considerable field work and extensive collections, various patterns of resource utilisation by thrips emerged.

Thrips and Flowers
The native thrips fauna in flowers remains poorly known. In much of the southern half of Australia this habitat is dominated by the plague thrips, Thrips imaginis, although north of Brisbane this species is replaced by the closely related Thrips safrus. In the eastern rainforests the most common flower thrips is Thrips setipennis, but in the flowers of Eucalyptus and some other Myrtaceae Thrips australis predominates. Cranothrips, Odontothripiella and Thrips have each developed a range of host-specific species, but the biological significance of most of the described species placed in Pseudanaphothrips remains conjectural (Mound & Palmer 1981). Cycadothrips includes three described species that breed only in the male cones of Macrozamia cycads in eastern, western and central Australia, and the genus Anaphothrips and its relatives is known to involve at least 50 species that live in the flowers of many different species of plants.

Thrips as Pollinators
Kirk (1997) summarised the available information on pollination by thrips species, and indicated that the importance of these insects as pollinators had probably been overlooked. Since then other studies have emphasised the significance of thrips, including Williams et al. (2001) for a rainforest tree, Wilkiea huegeliana, in eastern Australia, and Mound & Terry (2001) for Macrozamia cycads. The close association of particular thrips species with particular flowers, coupled with the mobility of these insects, suggests that pollination by thrips is more general than has been proven experimentally. For example, Thrips knoxi is abundant in the flowers of various Lomandra species, and Thrips wellsae is abundant in the flowers of various Epacridaceae in the south-eastern mountains (Mound & Masumoto 2005), but only in New Guinea has pollination been demonstrated by a member of this genus (Zerega et al. (2004).

Thrips and Green Leaves
In the moist tropics and eastern coastal regions of Australia, many species of Phlaeothripidae are known to feed on green leaves or apical buds (Mound 2008b). Moreover, there are many such species in the dry areas, particularly on the foliage of Casuarina and Acacia species (Mound 1970; Crespi et al. 2004). Leaf-feeding Phlaeothripidae are usually host-specific, and thus few members of this family are considered pests. In contrast, some leaf-feeding species of Thripidae, Thripinae are polyphagous, with many introduced species being pests of non-native cultivated plants. Particularly noteworthy is the absence of thrips associated with the leaves of Eucalyptus species, the solitary exception being the polyphagous panchaetothripine species, Australothrips bicolor. The Thripidae subfamily Panchaetothripinae is primarily tropical in distribution, with few species occurring in southern Australia. Members of another thripid subfamily, the Dendrothripinae, are also leaf-feeding, and there are several endemic species and genera (Mound 1999). The fourth thripid subfamily, the Sericothripinae, is also well represented in Australia, with both native and introduced species.

Thrips and Galls
Minimising water loss is an esssential survival strategy for small insects in dry areas. Many thrips species achieve this either by inducing galls or else by invading galls induced by other insects. On some phyllodinous Acacia trees one suite of thrips species induces pouch galls, and some of these species are considered to be eusocial with a caste of non-breeding wingless individuals that function as soldiers to repel intruding insects, particularly a suite of kleptoparasitic thrips species (Crespi et al. 2004). An extensive suite of Phlaeothripidae species on Acacia trees invade galls and leaf mines induced by other insects, including Hymenoptera and Coleoptera. A further suite of species on these trees have the remarkable ability of glueing or sewing together two or more phyllodes to produce a domicile within which to breed (Bono & Crespi 2008), and these domiciles are invaded by a different group of kleptoparasitic thrips. The many galls on various trees of the eastern forests are little studied (Mound 2008b), but on several Casuarina tree species there are Phlaeothripidae that induce large woody galls; one of these in Western Australia is invaded by a kleptoparasitic thrips that is noteworthy for dimorphism in the male genitalia (Mound et al. 1999).

Thrips and Fungi
Fungi are available to thrips on the surface of dead twigs and branches, and also in leaf-litter on the ground. Both of these habitats are exploited in Australia, although the second probably includes the larger number of species. Not only are thrips on dead bark more exposed to desiccation, they are probably also more exposed to a wide range of predators such as birds, lizards, ants and spiders. As a result, these thrips species exist as widely dispersed populations, and are rarely collected (Mound, 2008b). Leaf-litter in Australia, even shallow Eucalyptus litter, often contains a wide range of thrips taxa. The completely wingless species in litter sometimes exist as a mosaic of slightly different looking forms, presumably due to limited gene flow between localised demes; their taxonomy remains particularly doubtful (Mound 1972). The members of one subfamily, Idolothripinae, feed only on fungal spores (Mound 2007).

Thrips as Predators
A few species of thrips, in all three major families, act as predators, and the range of prey includes thrips larvae, mites and their eggs, scale-insects and whitefly nymphs. These thrips are generally facultative predators, taking prey as well as feeding on plant tissues (Mound & Teulon 1995), as in various species of Aeolothripidae and also the pest species, Thrips tabaci and Frankliniella occidentalis. However, several groups of thrips are obligate predators, such as Aleurodothrips fasciapennis (Franklin) and some species of Karnyothrips that attack scale insects (Palmer & Mound 1991). Haplothrips bituberculatus, a widespread and common species apparently feeding on mites on dead branches, is a native predator, but Scolothrips sexmaculatus, that attacks mites on leaves, is introduced.

Introduced Thrips Species
Of the species of thrips recorded from Australia, at least 60 are introduced from other countries. This includes the common grass-living Thripidae of Europe, Aptinothrips, Chirothrips and Limothrips species, also the leaf-feeding tropical species such as those in the genera Chaetanaphothrips, Heliothrips, Hercinothrips, Parthenothrips, Selenothrips and some Scirtothrips and Thrips. Most of these probably have been established in Australia for many years, but more recent introductions are the Western Flower Thrips, Frankliniella occidentalis, the Oriental Rice Thrips, Stenchaetothrips biformis, the Melon Thrips, Thrips palmi, and the Lily-bulb Thrips, Liothrips vaneeckei. More difficult to evaluate are the increasing numbers of South-east Asian thrips species being newly recorded in Australia, such as Gynaikothrips ficorum, the leaf-rolling thrips of cultivated Ficus microcarpa trees (Mound 1996), the Oriental Lily-flower Thrips Taeniothrips eucharii (Mound & Tree, 2008), and the panchaetothripine Helionothrips errans that has been found at Perth and at Newcastle on orchid leaves. Given the continuing lack of knowledge of the thrips fauna of northern Australia, it is not possible to know if the northern coastal areas of this continent are part of the natural distribution of these and other Asian insects.

Faunal Relationships
Faunal relationships among Australian Thysanoptera are considered in Austin et al. (2004), but a large proportion of taxa are probably endemic. Despite this, in the Melanthripidae, the genus Dorythrips includes two species in Western Australia and one in Chile, whereas Cranothrips includes a series of species across Australia and one in South Africa. Similarly, Jacotia in the Phlaeothripidae has one species in South Africa and several in Australia (Mound 1995). Amongst the Phlaeothripidae, idolothripines such as Mecynothrips, Malesiathrips, Bactrothrips, Nesothrips and Carientothrips, show close relationships to the faunas of Papua New Guinea and the Pacific islands. In contrast, a few taxa show relationships to New Zealand (Mound 2006). Endemism, however, is also obvious. Thus of the 23 genera of Aeolothripidae worldwide, five are known only from Australia. In the Thripidae, the genera Odontothripiella and Pseudanaphothrips represent endemic Australian radiations, and this is also true of several new genera that are similar to Anaphothrips. In the semi-arid parts of Australia, the fauna of Phlaeothripidae includes several endemic radiations, including those on Acacia, Casuarina and Geijera (Mound 1971bet al.; Mound et al. 1999; Crespi et al. 2004).

Database Notes
The information on the Australian Faunal Directory site for the Thysanoptera originally was derived from the Zoological Catalogue of Australia, Volume 26, published on 22 May 1996 as (Mound 1996). Since then, it has been updated on several occasions, the most recent being in August 2010.

All species that are considered to have been validly recorded are included, together with all names that have been used for the Australian fauna. However, the many extralimital synonymies for certain widespread species are not included.

Common names follow Naumann (1993).

Limital Area
Distribution data in the Directory is by political and geographic region descriptors and serves as a guide to the distribution of a taxon. For details of a taxon's distribution, the reader should consult the cited references (if any) at genus and species levels.

Australia is defined as including Lord Howe Is., Norfolk Is., Cocos (Keeling) Ils, Christmas Is., Ashmore and Cartier Ils, Macquarie Is., Australian Antarctic Territory, Heard and McDonald Ils, and the waters associated with these land areas of Australian political responsibility. Political areas include the adjacent waters.

Terrestrial geographical terms are based on the drainage systems of continental Australia, while marine terms are self explanatory except as follows: the boundary between the coastal and oceanic zones is the 200 m contour; the Arafura Sea extends from Cape York to 124°E; and the boundary between the Tasman and Coral Seas is considered to be the latitude of Fraser Island, also regarded as the southern terminus of the Great Barrier Reef.

Distribution records, if any, outside of these areas are listed as extralimital. The distribution descriptors for each species are collated to genus level. Users are advised that extralimital distribution for some taxa may not be complete.

Diagnosis

Thrips differ from other insects in the asymmetry of their mouth parts. The right mandible does not develop beyond the embryo, although the left mandible forms an elongate, solid stylet in larvae and adults. The maxillary stylets (laciniae) are also asymmetric, and are linked together by a tongue and groove system to produce a (sometimes very long) feeding tube with a sub-apical aperture and one central channel.

On each leg, adult and larval thrips have an eversible, adhesive, pretarsal arolium, from which the old name Physapoda (bladder-foot) is derived. The modern ordinal name, Thysanoptera (fringe-wings), is derived from the long cilia that border the slender wings of adults, although in many species adults are wingless.

The life history of thrips is also unlike that of other insects. Following two actively feeding larval stages, there are two (or three, depending on the family) non-feeding pupal stages before the adult is produced. These pupal stages are found at ground level in most flower-living species, but normally occur on the food substrate in leaf- and fungus-feeding species..