- For the type genus
In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...
, see Thrips (genus)Thrips is a genus of thrips.-Ecology:Species in the genus Thrips feed on pollen, and can be major agricultural pests, with several being vectors of tospoviruses.-Etymology:...
.
Thrips (Order
Thysanoptera) are tiny, slender
insectInsects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s with fringed wings (thus the
scientific nameBinomial nomenclature is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages...
, from the
GreekGreek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
thysanos (fringe) + pteron (wing)). Other common names for thrips include
thunderflies,
thunderbugs,
storm flies,
thunderblights, and
corn lice. Thrips species feed on a large variety of sources, both plant and animal, by
puncturingIn coding theory, puncturing is the process of removing some of the parity bits after encoding with an error-correction code. This has the same effect as encoding with an error-correction code with a higher rate, or less redundancy...
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
miteMites, along with ticks, are small arthropods belonging to the subclass Acari and the class Arachnida. The scientific discipline devoted to the study of ticks and mites is called acarology.-Diversity and systematics:...
s and are considered beneficial, while some feed on fungal spores or pollen. So far around 5,000 species have been described. Thrips are generally tiny (1 mm long or less) and are not good flyers, although they can be carried long distances by the wind. In the right conditions, many species can exponentially increase in population size and form large swarms, making them an irritation to humans.
Like the words sheep, swan or moose, the word thrips is used for both the singular and plural
formsIn linguistics, grammatical number is a grammatical category of nouns, pronouns, and adjective and verb agreement that expresses count distinctions ....
. So while there may be many thrips there can also be a solitary thrips. The word thrips is from the Greek, meaning wood louse.
Characteristics
They are small hemimetabolic insects with a distinctive cigar-shaped bauplan: elongate with transversely constricted bodies. They range in size from 0.5 to 14 mm (0.0196850393700787 to 0.551181102362205 in) in length for the larger predatory thrips, but most thrips are approximately a millimetre 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
tarsalThe arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa , trochanter , femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus ,...
segments with a bladder-like structure known as an arolium at the pretarsus. This structure can be everted by means of
hemolymphHemolymph, or haemolymph, is a fluid in the circulatory system of some arthropods and is analogous to the fluids and cells making up both blood and interstitial fluid in vertebrates such as birds and mammals...
pressure, enabling the insect to walk on vertical surfaces.
Thrips have asymmetrical
mouthpartInsects exhibit a range of mouthparts, adapted to particular modes of feeding. The earliest insects had chewing mouthparts...
s that are also unique to the group. Unlike the
HemipteraHemiptera is an order of insects most often known as the true bugs , comprising around 50,000–80,000 species of cicadas, aphids, planthoppers, leafhoppers, shield bugs, and others...
, the right
mandiblethumb|250px|The mandibles of a [[Bull ant]]The mandible of an arthropod is either of a pair of mouthparts used for biting, cutting and holding food. Mandibles are often simply referred to as jaws. Mandibles are present in the extant subphyla Myriapoda , Crustacea and Hexapoda...
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. Some species may then inject digestive enzymes as the maxillary stylets and hypopharynx are inserted into the opening to drain cellular fluids. This process leaves a distinctive silvery or bronze scarring on the surface of the stems or leaves where the thrips feed.
Thysanoptera is divided into two suborders: Terebrantia, and Tubulifera. These two suborders 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
ovipositorThe ovipositor is an organ used by some animals for oviposition, i.e., the laying of eggs. It consists of a maximum of three pairs of appendages formed to transmit the egg, to prepare a place for it, and to place it properly...
on the anteapical abdominal segment, lay eggs singly within plant tissue, and have two "pupal" stages.
Evolution and systematics
The Thysanoptera were first described in 1744 as a
genusIn biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Physapus by
De GeerBaron Charles de Geer was a Swedish industrialist and entomologist.- Life :...
, and then renamed Thrips by Linnaeus in 1758. In 1836
HalidayAlexander Henry Haliday, also known as Enrico Alessandro Haliday and Alexis Heinrich Haliday sometimes Halliday , was an Irish entomologist. He is primarily known for his work on Hymenoptera, Diptera and Thysanoptera, but Haliday worked on all insect orders and on many aspects of entomology.Haliday...
promoted the genus to the
taxonomic rankIn biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...
of
orderIn scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
, renaming them
Thysanoptera.
The earliest fossils of thrips date back to
PermianThe PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
(Permothrips longipennis Martynov, 1935). By the
Early CretaceousThe Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
true thrips became much more abundant. The extant
familyIn biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Merothripidae most resemble these ancestral Thysanoptera, and are probably basal to the order.
The following families are currently (2006) recognized:
- Suborder Terebrantia
- Adiheterothripidae Shumsher, 1946 (11 genera)
- Aeolothripidae
The Aeolothripidae are a family of thrips. They are particularly common in the holarctic region, although several occur in the drier parts of the subtropics, including dozens in Australia. Adults and larvae are usually found in flowers, but they pupate on the ground...
Uzel, 1895 (29 genera) - banded thrips and broad-winged thrips
- Fauriellidae Priesner, 1949 (4 genera)
- †Hemithripidae Bagnall, 1923 (1 fossil genus, Hemithrips with 15 species)
- Heterothripidae Bagnall, 1912 (7 genera)
- † Jezzinothripidae zur Strassen, 1973 (included by some authors in Merothripidae)
- †Karataothripidae Sharov, 1972 (1 fossil species, Karataothrips jurassicus)
- Melanthripidae Bagnall, 1913 (6 genera)
- Merothripidae Hood, 1914 (5 genera) - large-legged thrips
- † Scudderothripidae zur Strassen, 1973 (included by some authors in Stenurothripidae)
- Thripidae
The Thripidae are the most speciose family of thrips, with over 290 genera representing just over two thousand species. They can be distinguished from other thrips by a saw-like ovipositor curving downwards, narrow wings with two veins, and antennae of six to ten antennomeres with stiletto-like...
Stevens, 1829 (292 genera in four subfamilies) - common thrips
- † Triassothripidae Grimaldi & Shmakov, 2004 (2 fossil genera)
- Uzelothripidae Hood, 1952 (1 species, Uzelothrips scabrosus)
- Suborder Tubulifera
- Phlaeothripidae
Phlaeothripidae is a family of thrips with hundreds of genera. They are the only family of the suborder Tubulifera, and are themselves ordered into two subfamilies, the Idolothripinae with 80 genera, and the Phlaeothripinae with almost 400...
(447 genera in two subfamilies)
Ecology
Natural history
Thrips are believed to have descended from a mycetophilic ancestor during the Mesozoic, 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. 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.
Flower-feeding thrips may be responsible for pollination while feeding, 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 there remains varying degrees of fidelity to a described host. Family
ThripidaeThe Thripidae are the most speciose family of thrips, with over 290 genera representing just over two thousand species. They can be distinguished from other thrips by a saw-like ovipositor curving downwards, narrow wings with two veins, and antennae of six to ten antennomeres with stiletto-like...
is particularly notorious for members with broad host ranges, and the majority of pest thrips come from this family.
While poorly documented, chemical communication is believed to be important to the group. Anal secretions are produced in the hindgut, and released along the posterior setae as predator deterrents. Some Phlaeothripidae form
eusocialEusociality is a term used for the highest level of social organization in a hierarchical classification....
groups similar to
antAnts are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
-colonies, with reproductive
queensA queen ant is an adult, reproducing female ant in an ant colony; generally she will be the mother of all the other ants in that colony. Some female ants do not need to mate to produce offspring, reproducing through asexual parthenogenesis or cloning and all of those offspring will be female.Ant...
and non-reproductive soldier castes. Many thrips form
gallGalls or cecidia are outgrowths on the surface of lifeforms caused by invasion by other lifeforms, such as parasites or bacterial infection. Plant galls are abnormal outgrowths of plant tissues and can be caused by various parasites, from fungi and bacteria, to insects and mites...
s on plants when feeding or laying their eggs.
Life cycle
The rate at which thrips move through their developmental cycle is highly dependent upon environmental conditions, including the temperature and nutrient quality of their food source. Thrips begin their lives as eggs. These are extremely small (about 0.2 mm long) and kidney-shaped. It may take from as little as a day to several weeks before hatching. 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 surface of plants. Thrips then pass through two wingless
instarAn instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...
s of nymph.
As hemimetabolous insects, the Thysanoptera do not actually undergo
complete metamorphosisHolometabolism, also called complete metamorphism, is a term applied to insect groups to describe the specific kind of insect development which includes four life stages - as an embryo or egg, a larva, a pupa and an imago or adult. Holometabolism is a monophyletic trait that all insects in the...
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 plant, hiding in the tightly packed bud of flowers 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-budsAn imaginal disc is one of the parts of a holometabolous insect larva that will become a portion of the outside of the adult insect during the pupal transformation. Contained within the body of the larva, there are pairs of discs that will form, for instance, the wings or legs or antennae or other...
and reproductive structures will grow and mature into their adult forms.
All described genera of thrips are haplodiploid organisms capable of
parthenogenesisParthenogenesis is a form of asexual reproduction found in females, where growth and development of embryos occur without fertilization by a male...
, with some favoring
arrhenotokyArrhenotoky or arrhenotokous parthenogenesis is a form of parthenogenesis in which unfertilized eggs develop into haploid males.This form is observed in some marine invertebrates, beetles, scorpions, mites, bees, etc....
and others displaying
thelytokyThelytoky comes from the Greek thely, meaning "female", and tokos, meaning "birth". Thelytokous parthenogenesis is a type of parthenogenesis in which females are produced from unfertilized eggs. It is rare in the animal kingdom and has only been reported in about 1500 species...
, although it remains possible that the sex-determining bacterial
endosymbiontAn endosymbiont is any organism that lives within the body or cells of another organism, i.e. forming an endosymbiosis...
WolbachiaWolbachia is a genus of bacteria which infects arthropod species, including a high proportion of insects , as well as some nematodes. It is one of the world's most common parasitic microbes and is possibly the most common reproductive parasite in the biosphere...
may also play a role in defining sex-ratios for some populations of thrips. Several normally bisexual species have become established in the United States with only members of a single sex present.
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.
Human impact
Many thrips are pests of commercial crops due to the damage caused by feeding on developing flowers or vegetables, causing discoloration, deformities, and reduced marketability of the crop. Thrips may also serve as vectors for plant diseases, such as Tospoviruses. Over 20 plant infecting viruses are known to be transmitted by thrips. These enveloped viruses are considered among some of the most damaging of emerging plant pathogens around the world. Virus members include the tomato spotted wilt virus and the Impatiens necrotic spot viruses. The western flower thrips,
Frankliniella occidentalisThe western flower thrips is an important pest insect in agriculture. This species of thrips is native to North America but has spread to other continents including Europe, Australia, and South America via transport of infested plant material...
, now has a worldwide distribution and is considered the primary vector of plant diseases caused by Tospoviruses.
This global explosion in thrips species' range is not uncommon, as their small size and predisposition towards enclosed places makes them difficult to detect by phytosanitary inspection. When coupled with the increasing
globalizationGlobalization refers to the increasingly global relationships of culture, people and economic activity. Most often, it refers to economics: the global distribution of the production of goods and services, through reduction of barriers to international trade such as tariffs, export fees, and import...
of trade and the growth of
greenhouseA greenhouse is a building in which plants are grown. These structures range in size from small sheds to very large buildings...
agriculture, it is no surprise that thrips are among the fastest growing group of
invasive species"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
in the world. Examples include
Scirtothrips dorsalisThe chilli thripsThis is the more common international spelling of "chilli" outside of the United States. This spelling has been preserved in the common name for the insect by entomologists in the United States in deference to the body of literature already published for this species by...
and
Thrips palmiThrips palmi is an insect from the Thrips genus .It is a primary vector of plant viruses. Also known as the melon thrips, T...
.
Flower feeding thrips are routinely attracted to bright floral colors (including white, blue, and especially yellow), and will land and attempt to feed. It is not uncommon for some species (e.g., Frankliniella tritici and Limothrips cerealium) to "bite" humans under such circumstances. Although no species feed on blood and there is no known animal disease vectored by thrips, some skin irritation has been described.
Due to their small size and thigmotaxic behavior, many persons first encounter thrips when shelter-seeking insects become trapped within the glass panes of their LCD monitors.
Management
Due to their small size and high rate of reproduction, thrips are difficult to control using
classical biological controlBiological control of pests in agriculture is a method of controlling pests that relies on predation, parasitism, herbivory, or other natural mechanisms...
. All predators must be small and slender enough to penetrate the crevices that thrips hide in while feeding, and then prey extensively on eggs and larvae. Only two families of
parasitoidA parasitoid is an organism that spends a significant portion of its life history attached to or within a single host organism in a relationship that is in essence parasitic; unlike a true parasite, however, it ultimately sterilises or kills, and sometimes consumes, the host...
hymenoptera Hymenoptera is one of the largest orders of insects, comprising the sawflies, wasps, bees and ants. There are over 130,000 recognized species, with many more remaining to be described. The name refers to the heavy wings of the insects, and is derived from the Ancient Greek ὑμήν : membrane and...
are known to parasitize eggs and larvae, the
EulophidaeEulophidae is a large family of hymenopteran insects, with over 4,300 described species in some 300 genera . The family as presently defined also includes the genus Elasmus, which was previously treated as a separate family, "Elasmidae", and is now treated as a subfamily of Eulophidae...
and the
TrichogrammatidaeThe family Trichogrammatidae are tiny wasps in the Chalcidoidea that include some of the smallest of all insects, with most species having adults less than 1 mm in length. There are over 840 species in ca. 80 genera worldwide. Trichogrammatids parasitize the eggs of many different orders of insects...
. Other biocontrol agents of adults and larvae include aphid wasps,
anthocorid bugsThe Anthocoridae are a family of bugs, commonly called minute pirate bugs or flower bugs.-Name:The vernacular name probably stems from the notion that these very small animals can do much pain to humans, just like small pirate vessels can do so to big ships.The scientific name is a combination of...
of genus
OriusThe genus Orius consists of omnivorous bugs in the family Anthocoridae . Adults are 2–5 mm long and feed mostly on spider mites, thrips, and their eggs, but will also feed on pollen and vascular sap .These predators are common in gardens and landscapes...
, and
PhytoseiidPhytoseiidae is a family of mites which feed on thrips and other mite species. They are often used as a biological control agent for managing mite pests.-Subfamilies:* Amblyseiinae Muma, 1961* Phytoseiinae Berlese, 1916* Typhlodrominae Scheuten, 1857...
mites. For this reason, many growers are occasionally forced to make limited use of pesticides to control thrips populations in the field and in greenhouses.
Another effective strategy for pest thrips are biological insecticides, including
Beauveria bassianaBeauveria bassiana is a fungus that grows naturally in soils throughout the world and acts as a parasite on various arthropod species, causing white muscardine disease; it thus belongs to the entomopathogenic fungi. It is being used as a biological insecticide to control a number of pests such as...
or Verticillium lecanii. These demonstrate a clear effect on eggs, larvae and adults of thrips.
External links
- Thrips links on the UF
The University of Florida is an American public land-grant, sea-grant, and space-grant research university located on a campus in Gainesville, Florida. The university traces its historical origins to 1853, and has operated continuously on its present Gainesville campus since September 1906...
/ IFASThe University of Florida’s Institute of Food and Agricultural Sciences is a federal-state-county partnership dedicated to developing knowledge in agriculture, human and natural resources, and the life sciences, and enhancing and sustaining the quality of human life by making that information...
Featured Creatures Web site