THYSANOPTERA (Thrips) Order Description
17 Sep 2016 15:52 #143
Thrips (order Thysanoptera) are minute, slender insects with fringed wings (thus the scientific name, from the Greek θύσανος thysanos ("fringe") + πτερόν pteron ("wing")).[1] Other common names for thrips include thunderflies, thunderbugs, storm flies, thunderblights, storm bugs, corn flies, corn lice and physopods. Thrips species feed on a large variety of plants and animals by puncturing them and sucking up the contents. A large number of thrips species are considered pests, because they feed on plants with commercial value. Some species of thrips feed on other insects or mites and are considered beneficial, while some feed on fungal spores or pollen. Approximately 6,000 species have been described. Thrips are generally tiny (1 mm long or less) and are not good flyers,[citation needed] although they can be carried long distances by the wind. In the right conditions, like indoor growing rooms or greenhouses, many species can exponentially increase in population size and form large swarms because of a lack of natural predators, making them an irritation to humans.
Like the words sheep, deer, and moose, the word thrips is used for both the singular and plural forms, so there may be many thrips or a single thrips.[2] The word thrips is from the Greek θρίψ, meaning "woodworm.
Morphology and classification[edit]
Thysanoptera diagram
Characteristics[edit]
Thrips are small hemimetabolic insects with a distinctive cigar-shaped bauplan. They are elongated with transversely constricted bodies. They range in size from 0.5 to 14 millimetres (0.020 to 0.551 in) in length for the larger predatory thrips, but most thrips are about 1 mm in length. Flight-capable thrips have two similar, strap-like pairs of wings with a ciliated fringe (from which the order derives its name). Their legs usually end in two tarsal segments with a bladder-like structure known as an "arolium" at the pretarsus. This structure can be everted by means of hemolymph pressure, enabling the insect to walk on vertical surfaces.[4][5]
Thrips have asymmetrical mouthparts that are also unique to the group. Unlike the Hemiptera, the right mandible of thrips is reduced and vestigial – and in some species completely absent. The left mandible is larger, and forms a narrow stylet used to pierce the cell wall of tissues.[6] Some species may then inject digestive enzymes as the maxillary stylets and hypopharynx are inserted into the opening to drain cellular fluids.[7][8] This process leaves a distinctive silvery or bronze scarring on the surfaces of the stems or leaves where the thrips feed.[9]
Thysanoptera is divided into two suborders: Terebrantia, and Tubulifera; these can be distinguished by morphological, behavioral, and developmental characteristics. Members of Tubulifera can be identified by their characteristic tube-shaped apical abdominal segment, egg-laying atop the surface of leaves, and three "pupal" stages. Females of the eight families of the Terebrantia all possess the eponymous saw-like ovipositor on the anteapical abdominal segment, lay eggs singly within plant tissue, and have two "pupal" stages.
Evolution and systematics[edit]
The Thysanoptera were first described in 1744 as a genus Physapus by De Geer, and then renamed Thrips by Linnaeus in 1758. In 1836 Haliday promoted the genus to the taxonomic rank of order, renaming them Thysanoptera. There are currently over six thousand species of thrips recognized, grouped into 777 extant genera and sixty fossil genera.[10]
The earliest fossils of thrips date back to Permian (Permothrips longipennis Martynov, 1935). By the Early Cretaceous, true thrips became much more abundant.[11] The extant family Merothripidae most resemble these ancestral Thysanoptera, and are probably basal to the order.[12]
These families are currently (2013) recognized:[13][14]
Suborder Terebrantia
Adiheterothripidae Shumsher, 1946 (11 genera)
Aeolothripidae Uzel, 1895 (29 genera) – banded thrips and broad-winged thrips
Fauriellidae Priesner, 1949 (four genera)
†Hemithripidae Bagnall, 1923 (one fossil genus, Hemithrips with 15 species)
Heterothripidae Bagnall, 1912 (seven genera)
† Jezzinothripidae zur Strassen, 1973 (included by some authors in Merothripidae)
†Karataothripidae Sharov, 1972 (one fossil species, Karataothrips jurassicus)
Melanthripidae Bagnall, 1913 (six genera)
Merothripidae Hood, 1914 (five genera) – large-legged thrips
† Scudderothripidae zur Strassen, 1973 (included by some authors in Stenurothripidae)
Thripidae Stevens, 1829 (292 genera in four subfamilies) – common thrips
† Triassothripidae Grimaldi & Shmakov, 2004 (two fossil genera)
Uzelothripidae Hood, 1952 (one species, Uzelothrips scabrosus)
Suborder Tubulifera
Phlaeothripidae (447 genera in two subfamilies)
Bhatti provides an alternative classification based on morphological characters that would split the group into two orders and forty different families.[15][16][17] This classification has been less accepted by taxonomists as it can be derailed by convergent evolution and does not follow phylogenetic principles of classification.
Ecology[edit]
Scanning electron micrograph of a thrips (Thysanoptera), showing fine structure, the compound eyes, wing construction, and setae. Scale bar represents 10 μm.
Natural history[edit]
Thrips are believed to have descended from a mycetophilic (fungus-feeding) ancestor during the Mesozoic,[11] and many groups still feed upon and inadvertently redistribute fungal spores, but most research has focused on those species feeding on or in association with economically significant crops. Some thrips are predatory, but the majority are phytophagous insects feeding on pollen and the chloroplasts harvested from the outer layer of plant epidermal and mesophyll cells.[9][18] These species are minute organisms that prefer to feed within the tightly packed apical buds of new growth. Feeding usually occurs along the main vein or ribs of leaves and petals.[19][20]
Flower-feeding thrips may be responsible for pollination while feeding,[21][22][23][24][25] but their most obvious contribution to their ecosystem remains the damage they can cause during feeding. This impact may fall across a broad selection of prey items, as there is considerable breadth in host affinity across the order, and even within a species, varying degrees of fidelity to a described host remain.[18][26] Family Thripidae is particularly notorious for members with broad host ranges, and the majority of pest thrips come from this family.[27][28]
While poorly documented, chemical communication is believed to be important to the group.[29] Anal secretions are produced in the hindgut,[30] and released along the posterior setae as predator deterrents.[19][30][31] Many thrips form galls on plants when feeding or laying their eggs. Some of the gall-forming Phlaeothripidae, such as genera Kladothrips[32] and Oncothrips[33] form eusocial groups similar to ant colonies, with reproductive queens and nonreproductive soldier castes.[34][35][36]
Lifecycle[edit]
The rate at which thrips move through their developmental cycles is highly dependent upon environmental conditions, including the temperature and nutrient quality of their food sources. Thrips begin their lives as eggs. These are extremely small (about 0.2 mm long) and kidney-shaped. Hatching may take from as little as a day to several weeks. The females of the suborder Terebrantia are equipped with an ovipositor, which they use to cut slits in plant tissue and then insert their eggs, one per slit. Females of the suborder Tubulifera lack an ovipositor and lay their eggs singly or in small groups on the outside surfaces of plants. Thrips then pass through two wingless instars of nymph.
Nymph stage
As hemimetabolous insects, the Thysanoptera do not actually undergo complete metamorphosis, but pass through a similar stage in which they do not feed and are mostly immobile. Both suborders of thrips will first enter a short prepupal stage lasting a day at most, during which they will seek out dark crevices on plants, hiding in the tightly packed flower buds or bark – or drop off of the plant entirely, burrowing into leaf litter or loose soil. Some thrips will then construct a pupal cell or cocoon. In Terebrantian thrips, a single pupal instar follows, whereas in the Tubulifera, two pupal stages will follow. During these stages, wing-buds and reproductive structures will grow and mature into their adult forms.
All described genera of thrips are haplodiploid organisms capable of parthenogenesis, with some favoring arrhenotoky and others displaying thelytoky.[19][20][37] In some cases the sex-determining bacterial endosymbiont Wolbachia plays a role in defining the reproductive mode for some populations of thrips.[26][37][38] Several normally bisexual species have become established in the United States with only members of a single sex present.[19][20][37][39]
When mating occurs, it may last from minutes to hours. Most female thrips have a preoviposition period lasting from a day to a week during which their eggs mature, and before which they cannot mate.
Thrips (order Thysanoptera) are minute, slender insects with fringed wings (thus the scientific name, from the Greek θύσανος thysanos ("fringe") + πτερόν pteron ("wing")).[1] Other common names for thrips include thunderflies, thunderbugs, storm flies, thunderblights, storm bugs, corn flies, corn lice and physopods. Thrips species feed on a large variety of plants and animals by puncturing them and sucking up the contents. A large number of thrips species are considered pests, because they feed on plants with commercial value. Some species of thrips feed on other insects or mites and are considered beneficial, while some feed on fungal spores or pollen. Approximately 6,000 species have been described. Thrips are generally tiny (1 mm long or less) and are not good flyers,[citation needed] although they can be carried long distances by the wind. In the right conditions, like indoor growing rooms or greenhouses, many species can exponentially increase in population size and form large swarms because of a lack of natural predators, making them an irritation to humans.
Like the words sheep, deer, and moose, the word thrips is used for both the singular and plural forms, so there may be many thrips or a single thrips.[2] The word thrips is from the Greek θρίψ, meaning "woodworm.
Morphology and classification[edit]
Thysanoptera diagram
Characteristics[edit]
Thrips are small hemimetabolic insects with a distinctive cigar-shaped bauplan. They are elongated with transversely constricted bodies. They range in size from 0.5 to 14 millimetres (0.020 to 0.551 in) in length for the larger predatory thrips, but most thrips are about 1 mm in length. Flight-capable thrips have two similar, strap-like pairs of wings with a ciliated fringe (from which the order derives its name). Their legs usually end in two tarsal segments with a bladder-like structure known as an "arolium" at the pretarsus. This structure can be everted by means of hemolymph pressure, enabling the insect to walk on vertical surfaces.[4][5]
Thrips have asymmetrical mouthparts that are also unique to the group. Unlike the Hemiptera, the right mandible of thrips is reduced and vestigial – and in some species completely absent. The left mandible is larger, and forms a narrow stylet used to pierce the cell wall of tissues.[6] Some species may then inject digestive enzymes as the maxillary stylets and hypopharynx are inserted into the opening to drain cellular fluids.[7][8] This process leaves a distinctive silvery or bronze scarring on the surfaces of the stems or leaves where the thrips feed.[9]
Thysanoptera is divided into two suborders: Terebrantia, and Tubulifera; these can be distinguished by morphological, behavioral, and developmental characteristics. Members of Tubulifera can be identified by their characteristic tube-shaped apical abdominal segment, egg-laying atop the surface of leaves, and three "pupal" stages. Females of the eight families of the Terebrantia all possess the eponymous saw-like ovipositor on the anteapical abdominal segment, lay eggs singly within plant tissue, and have two "pupal" stages.
Evolution and systematics[edit]
The Thysanoptera were first described in 1744 as a genus Physapus by De Geer, and then renamed Thrips by Linnaeus in 1758. In 1836 Haliday promoted the genus to the taxonomic rank of order, renaming them Thysanoptera. There are currently over six thousand species of thrips recognized, grouped into 777 extant genera and sixty fossil genera.[10]
The earliest fossils of thrips date back to Permian (Permothrips longipennis Martynov, 1935). By the Early Cretaceous, true thrips became much more abundant.[11] The extant family Merothripidae most resemble these ancestral Thysanoptera, and are probably basal to the order.[12]
These families are currently (2013) recognized:[13][14]
Suborder Terebrantia
Adiheterothripidae Shumsher, 1946 (11 genera)
Aeolothripidae Uzel, 1895 (29 genera) – banded thrips and broad-winged thrips
Fauriellidae Priesner, 1949 (four genera)
†Hemithripidae Bagnall, 1923 (one fossil genus, Hemithrips with 15 species)
Heterothripidae Bagnall, 1912 (seven genera)
† Jezzinothripidae zur Strassen, 1973 (included by some authors in Merothripidae)
†Karataothripidae Sharov, 1972 (one fossil species, Karataothrips jurassicus)
Melanthripidae Bagnall, 1913 (six genera)
Merothripidae Hood, 1914 (five genera) – large-legged thrips
† Scudderothripidae zur Strassen, 1973 (included by some authors in Stenurothripidae)
Thripidae Stevens, 1829 (292 genera in four subfamilies) – common thrips
† Triassothripidae Grimaldi & Shmakov, 2004 (two fossil genera)
Uzelothripidae Hood, 1952 (one species, Uzelothrips scabrosus)
Suborder Tubulifera
Phlaeothripidae (447 genera in two subfamilies)
Bhatti provides an alternative classification based on morphological characters that would split the group into two orders and forty different families.[15][16][17] This classification has been less accepted by taxonomists as it can be derailed by convergent evolution and does not follow phylogenetic principles of classification.
Ecology[edit]
Scanning electron micrograph of a thrips (Thysanoptera), showing fine structure, the compound eyes, wing construction, and setae. Scale bar represents 10 μm.
Natural history[edit]
Thrips are believed to have descended from a mycetophilic (fungus-feeding) ancestor during the Mesozoic,[11] and many groups still feed upon and inadvertently redistribute fungal spores, but most research has focused on those species feeding on or in association with economically significant crops. Some thrips are predatory, but the majority are phytophagous insects feeding on pollen and the chloroplasts harvested from the outer layer of plant epidermal and mesophyll cells.[9][18] These species are minute organisms that prefer to feed within the tightly packed apical buds of new growth. Feeding usually occurs along the main vein or ribs of leaves and petals.[19][20]
Flower-feeding thrips may be responsible for pollination while feeding,[21][22][23][24][25] but their most obvious contribution to their ecosystem remains the damage they can cause during feeding. This impact may fall across a broad selection of prey items, as there is considerable breadth in host affinity across the order, and even within a species, varying degrees of fidelity to a described host remain.[18][26] Family Thripidae is particularly notorious for members with broad host ranges, and the majority of pest thrips come from this family.[27][28]
While poorly documented, chemical communication is believed to be important to the group.[29] Anal secretions are produced in the hindgut,[30] and released along the posterior setae as predator deterrents.[19][30][31] Many thrips form galls on plants when feeding or laying their eggs. Some of the gall-forming Phlaeothripidae, such as genera Kladothrips[32] and Oncothrips[33] form eusocial groups similar to ant colonies, with reproductive queens and nonreproductive soldier castes.[34][35][36]
Lifecycle[edit]
The rate at which thrips move through their developmental cycles is highly dependent upon environmental conditions, including the temperature and nutrient quality of their food sources. Thrips begin their lives as eggs. These are extremely small (about 0.2 mm long) and kidney-shaped. Hatching may take from as little as a day to several weeks. The females of the suborder Terebrantia are equipped with an ovipositor, which they use to cut slits in plant tissue and then insert their eggs, one per slit. Females of the suborder Tubulifera lack an ovipositor and lay their eggs singly or in small groups on the outside surfaces of plants. Thrips then pass through two wingless instars of nymph.
Nymph stage
As hemimetabolous insects, the Thysanoptera do not actually undergo complete metamorphosis, but pass through a similar stage in which they do not feed and are mostly immobile. Both suborders of thrips will first enter a short prepupal stage lasting a day at most, during which they will seek out dark crevices on plants, hiding in the tightly packed flower buds or bark – or drop off of the plant entirely, burrowing into leaf litter or loose soil. Some thrips will then construct a pupal cell or cocoon. In Terebrantian thrips, a single pupal instar follows, whereas in the Tubulifera, two pupal stages will follow. During these stages, wing-buds and reproductive structures will grow and mature into their adult forms.
All described genera of thrips are haplodiploid organisms capable of parthenogenesis, with some favoring arrhenotoky and others displaying thelytoky.[19][20][37] In some cases the sex-determining bacterial endosymbiont Wolbachia plays a role in defining the reproductive mode for some populations of thrips.[26][37][38] Several normally bisexual species have become established in the United States with only members of a single sex present.[19][20][37][39]
When mating occurs, it may last from minutes to hours. Most female thrips have a preoviposition period lasting from a day to a week during which their eggs mature, and before which they cannot mate.
Please Log in to join the conversation.
Optimized FB Like Button
O-Sense
Time to create page: 0.321 seconds
