Thrips (
order Thysanoptera) are minute (mostly long or less), slender
insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...
s with fringed wings and unique asymmetrical mouthparts. Different thrips species feed mostly on plants by puncturing and sucking up the contents, although a few are predators.
Entomologists
Entomology () is the scientific study of insects, a branch of zoology. In the past the term "insect" was less specific, and historically the definition of entomology would also include the study of animals in other arthropod groups, such as arach ...
have
described approximately 6,000 species. They fly only weakly and their feathery wings are unsuitable for conventional flight; instead, thrips exploit an unusual mechanism,
clap and fling, to create lift using an unsteady circulation pattern with transient
vortices
In fluid dynamics, a vortex ( : vortices or vortexes) is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices form in stirred fluids, and may be observed in smoke rings, whirlpools in th ...
near the wings.
Many thrips species are
pests of commercially important crops. A few species serve as
vectors for over 20 viruses that cause
plant disease
Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomy ...
, especially the
Tospoviruses
''Orthotospovirus'' is a genus of negative-strand RNA viruses, in the family ''Tospoviridae'' of the order ''Bunyavirales,'' which infects plants. Tospoviruses take their name from the species '' Tomato spotted wilt orthotospovirus'' (TSWV) which ...
. Some species of thrips are beneficial as pollinators or as predators of other insects or
mite
Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear evid ...
s. In the right conditions, such as in greenhouses, many species can exponentially increase in population size and form large swarms because of a lack of natural predators coupled with their ability to reproduce asexually, making them destructive to crops. In addition to damaging plants, thrips may invade houses and infest household objects such as furniture, bedding and computer monitors – in the latter case by forcing their way in between the
LCD and its glass covering.
Their identification to species by standard morphological characteristics is often challenging.
Etymology
The first recorded mention of thrips is from the 17th century and a sketch was made by Philippo Bonanni, a Catholic priest, in 1691. Swedish entomologist Baron
Charles De Geer
Baron Charles de Geer (the family is usually known as De Geer with a capitalized "De" and is pronounced "de yer"); Finspång in Risinge 30 January 1720 – Stockholm 7 March 1778) was a Swedish industrialist and entomologist.
Life
De Geer, w ...
described two species in the
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
''Physapus'' in 1744 and
Linnaeus
Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...
in 1746 added a third species and named this group of insects ''Thrips''. In 1836 the Irish entomologist
Alexander Henry Haliday
Alexander Henry Haliday (1806–1870, also known as Enrico Alessandro Haliday, Alexis Heinrich Haliday, or simply Haliday) was an Irish entomologist. He is primarily known for his work on Hymenoptera, Diptera, and Thysanoptera, but worked on ...
described 41 species in 11 genera and proposed the
order name of Thysanoptera. The first monograph on the group was published in 1895 by
Heinrich Uzel who is considered the father of Thysanoptera studies.
The generic and English name ''thrips'' is a direct transliteration of the ancient Greek , ''thrips'', meaning "woodworm". Like some other animal names such as ''sheep'', ''deer'', and ''moose'', in English the word thrips is both the singular and plural
forms
Form is the shape, visual appearance, or configuration of an object. In a wider sense, the form is the way something happens.
Form also refers to:
*Form (document), a document (printed or electronic) with spaces in which to write or enter data
* ...
, so there may be many thrips or a single thrips. Other common names for thrips include thunderflies, thunderbugs, storm flies, thunderblights, storm bugs, corn fleas, corn flies, corn lice, freckle bugs, harvest bugs, and physopods.
The older group name "physopoda" is with reference to the bladder like tips to the
tarsi of the legs. The name of the order Thysanoptera is constructed from the ancient Greek words , ''thysanos'', "tassel or fringe", and , ''pteron'', "wing", for the insects' fringed wings.
Morphology
![Thrips physapus](https://upload.wikimedia.org/wikipedia/commons/8/8c/Thrips_physapus.jpg)
Thrips are small
hemimetabolic insects with a distinctive cigar-shaped
body plan
A body plan, ( ), or ground plan is a set of morphological features common to many members of a phylum of animals. The vertebrates share one body plan, while invertebrates have many.
This term, usually applied to animals, envisages a "blueprin ...
. They are elongated with transversely constricted bodies. They range in size from 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 fringe of bristles. The wings are folded back over the body at rest. 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
Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod (invertebrate) body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which ...
pressure, enabling the insect to walk on vertical surfaces.
They have compound eyes consisting of a small number of ommatidia and three ocelli or simple eyes on the head.
![Heliothrips asymmetric mouthparts](https://upload.wikimedia.org/wikipedia/commons/7/7b/Heliothrips_asymmetric_mouthparts.jpg)
Thrips have asymmetrical
mouthparts unique to the group. Unlike the
Hemiptera
Hemiptera (; ) is an order (biology), order of insects, commonly called true bugs, comprising over 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, Reduviidae, assassin bugs, Cimex, bed bugs, and shield bugs. ...
(true bugs), the right
mandible
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...
of thrips is reduced and vestigial – and in some species completely absent.
The left mandible is used briefly to cut into the food plant; saliva is injected and the maxillary stylets, which form a tube, are then inserted and the semi-digested food pumped from ruptured cells. This process leaves cells destroyed or collapsed, and a distinctive silvery or bronze scarring on the surfaces of the stems or leaves where the thrips have fed.
Thysanoptera is divided into two suborders, Terebrantia and Tubulifera; these can be distinguished by morphological, behavioral, and developmental characteristics. Tubulifera consists of a single family,
Phlaeothripidae
Phlaeothripidae is a family of thrips with hundreds of genera. They are the only extant family of the suborder Tubulifera, alongside the extinct family Rohrthripidae and are themselves ordered into two subfamilies, the Idolothripinae with 80 g ...
; members can be identified by their characteristic tube-shaped apical abdominal segment, egg-laying atop the surface of leaves, and three "pupal" stages. In the Phlaeothripidae, the males are often larger than females and a range of sizes may be found within a population. The largest recorded phlaeothripid species is about 14 mm long. Females of the eight families of the Terebrantia all possess the eponymous saw-like (see
terebra
''Terebra'' is a genus of small to large-sized predatory sea snails, marine gastropod molluscs in the subfamily Terebrinae of the family Terebridae, the auger snails.
Species in this genus do not possess a radula.
Species
Species in the gen ...
)
ovipositor
The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typical ...
on the anteapical abdominal segment, lay eggs singly within plant tissue, and have two "pupal" stages. In most Terebrantia, the males are smaller than females. The family Uzelothripidae has a single species and it is unique in having a whip-like terminal antennal segment.
Evolution
The earliest fossils of thrips date back to the
Permian
The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...
(''
Permothrips longipennis''). By the
Early Cretaceous
The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma.
Geology
Pro ...
, true thrips became much more abundant.
[ The extant ]family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
Merothripidae
Merothripidae is a family of thrips in the order Thysanoptera. There are at least 4 genera and 20 described species in Merothripidae.
Genera
These four genera belong to the family Merothripidae:
* '' Damerothrips'' Hood, 1954
* '' Merothrips'' H ...
most resembles these ancestral Thysanoptera, and is probably basal to the order. There are currently over six thousand species of thrips recognized, grouped into 777 extant and sixty fossil genera.
Phylogeny
Thrips are generally considered to be the sister group to Hemiptera
Hemiptera (; ) is an order (biology), order of insects, commonly called true bugs, comprising over 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, Reduviidae, assassin bugs, Cimex, bed bugs, and shield bugs. ...
(bugs).
The phylogeny of thrips families has been little studied. A preliminary analysis in 2013 of 37 species using 3 genes, as well as a phylogeny based on ribosomal DNA and three proteins in 2012, supports the monophyly of the two suborders, Tubulifera and Terebrantia. In Terebrantia, Melanothripidae may be sister to all other families, but other relationships remain unclear. In Tubulifera, the Phlaeothripidae and its subfamily Idolothripinae are monophyletic. The two largest thrips subfamilies, Phlaeothripinae and Thripinae, are paraphyletic and need further work to determine their structure. The internal relationships from these analyses are shown in the cladogram.
Taxonomy
The following families are currently (2013) recognized:
* Suborder Terebrantia
Terebrantia is a suborder of thrips (order Thysanoptera). Order Thysanoptera includes 5,500 species classified into two suborders distinguished by the ovipositor. Terebrantia have a well-developed conical ovipositor, while the Tubulifera do not. ...
:* Adiheterothripidae
Adiheterothripidae is a family of thrips belonging to the order Thysanoptera.
Genera:
* ''Exitelothrips'' Strassen, 1973
* ''Neocomothrips'' Strassen, 1973
* ''Progonothrips'' Strassen, 1973
* ''Rhetinothrips'' Strassen, 1973
* ''Scaphothrips'' S ...
(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 ...
(29 genera) – banded thrips and broad-winged thrips
:* Fauriellidae (four genera)
:* † Hemithripidae (one fossil genus, '' Hemithrips'' with 15 species)
:* Heterothripidae
Heterothripidae is a family of thrips in the order Thysanoptera
Thrips (order Thysanoptera) are minute (mostly long or less), slender insects with fringed wings and unique asymmetrical mouthparts. Different thrips species feed mostly on pl ...
(seven genera, restricted to the New World)
:* † Jezzinothripidae (included by some authors in Merothripidae
Merothripidae is a family of thrips in the order Thysanoptera. There are at least 4 genera and 20 described species in Merothripidae.
Genera
These four genera belong to the family Merothripidae:
* '' Damerothrips'' Hood, 1954
* '' Merothrips'' H ...
)
:* † Karataothripidae (one fossil species, '' Karataothrips jurassicus'')
:* Melanthripidae
Melanthripidae is a family of thrips belonging to the order Thysanoptera
Thrips (order Thysanoptera) are minute (mostly long or less), slender insects with fringed wings and unique asymmetrical mouthparts. Different thrips species feed most ...
(six genera of flower feeders)
:* Merothripidae
Merothripidae is a family of thrips in the order Thysanoptera. There are at least 4 genera and 20 described species in Merothripidae.
Genera
These four genera belong to the family Merothripidae:
* '' Damerothrips'' Hood, 1954
* '' Merothrips'' H ...
(five genera, mostly Neotropical and feeding on dry-wood fungi) – large-legged thrips
:* † Scudderothripidae (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 ante ...
(292 genera in four subfamilies, flower living) – common thrips
:* † Triassothripidae (two fossil genera)
:* Uzelothripidae
''Uzelothrips'' is a genus of thrips, and the only genus in the family Uzelothripidae. Up until 2012 it contained a single species, ''U. scabrosus'', known from Belém, Brazil; Brisbane, Australia; Singapore, and Angola. In 2012 a new extinct sp ...
(one species, ''Uzelothrips scabrosus
''Uzelothrips'' is a genus of thrips, and the only genus in the family Uzelothripidae. Up until 2012 it contained a single species, ''U. scabrosus'', known from Belém, Brazil; Brisbane, Australia; Singapore, and Angola. In 2012 a new extinct spe ...
'')
* Suborder Tubulifera
Phlaeothripidae is a family of thrips with hundreds of genera. They are the only extant family of the suborder Tubulifera, alongside the extinct family Rohrthripidae and are themselves ordered into two subfamilies, the Idolothripinae with 80 g ...
:* Phlaeothripidae
Phlaeothripidae is a family of thrips with hundreds of genera. They are the only extant family of the suborder Tubulifera, alongside the extinct family Rohrthripidae and are themselves ordered into two subfamilies, the Idolothripinae with 80 g ...
(447 genera in two subfamilies, fungal hyphae and spore feeders)
The identification of thrips to species is challenging as types are maintained as slide preparations of varying quality over time. There is also considerable variability leading to many species being misidentified. Molecular sequence based approaches have increasingly been applied to their identification.
Biology
Feeding
Thrips are believed to have descended from a fungus-feeding ancestor during the Mesozoic, and many groups still feed upon and inadvertently redistribute fungal spores. These live among leaf litter or on dead wood and are important members of the ecosystem
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
, their diet often being supplemented with pollen
Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...
. Other species are primitively eusocial
Eusociality (from Greek εὖ ''eu'' "good" and social), the highest level of organization of sociality, is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping gen ...
and form plant galls and still others are predatory on mites and other thrips.[ Two species of ''Aulacothrips'', ''A. tenuis'' and ''A. levinotus'', have been found to be ectoparasites on aetalionid and membracid plant-hoppers in Brazil.
''Mirothrips arbiter'' has been found in paper wasp nests in Brazil. The eggs of the hosts including ''Mischocyttarus atramentarius'', ''Mischocyttarus cassununga'' and ''Polistes versicolor'' are eaten by the thrips. Thrips, especially in the family ]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 ...
, are also predators, and are considered beneficial in the management of pests like the codling moth
The codling moth (''Cydia pomonella'') is a member of the Lepidopteran family Tortricidae. They are major pests to agricultural crops, mainly fruits such as apples and pears. Because the larvae are not able to feed on leaves, they are highly d ...
s.
Most research has focused on thrips species that feed on economically significant crops. Some species are predatory, but most of them feed on pollen and the chloroplasts harvested from the outer layer of plant epidermal and mesophyll cells. They prefer tender parts of the plant, such as buds, flowers and new leaves. Besides feeding on plant tissues, the common blossom thrips feeds on pollen grains and on the eggs of mites. When the larva supplements its diet in this way, its development time and mortality is reduced, and adult females that consume mite eggs increase their fecundity and longevity.
Pollination
Some flower-feeding thrips pollinate the flowers they are feeding on, and some authors suspect that they may have been among the first insects to evolve a pollinating relationship with their host plants. ''Scirtothrips dorsalis
The 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 literat ...
'' carries pollen of commercially important chili pepper
Chili peppers (also chile, chile pepper, chilli pepper, or chilli), from Nahuatl '' chīlli'' (), are varieties of the berry-fruit of plants from the genus ''Capsicum'', which are members of the nightshade family Solanaceae, cultivated for ...
s. Darwin found that thrips could not be kept out by any netting when he conducted experiments by keeping away larger pollinators.
''Thrips setipennis'' is the sole pollinator of ''Wilkiea huegeliana
''Wilkiea huegeliana'' is a common small tree of rainforest in eastern Australia. Common names include common wilkiea, tetra beech, and veiny wilkiea. Originally described by French naturalist Louis René Tulasne, it was given its current name b ...
'', a small, unisexual annually flowering tree or shrub in the rainforests of eastern Australia. ''T. setipennis'' serves as an obligate pollinator for other Australian rainforest plant species, including ''Myrsine howittiana
''Myrsine howittiana'', the brush muttonwood or muttonwood, is a shrub or small tree in the family Primulaceae. The species is endemic to eastern Australia.
It grows to between 3 and 10 metres in height and has smooth, often whitish, bark. Th ...
'' and '' M. variabilis.'' The genus '' Cycadothrips'' is a specialist pollinator of cycad
Cycads are seed plants that typically have a stout and woody (ligneous) trunk with a crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants of a species are either male o ...
s, the cones of which are adapted for pollination by small insects. Thrips are likewise the primary pollinators of heathers in the family ''Ericaceae
The Ericaceae are a family of flowering plants, commonly known as the heath or heather family, found most commonly in acidic and infertile growing conditions. The family is large, with c.4250 known species spread across 124 genera, making it th ...
'', and play a significant role in the pollination of pointleaf manzanita. Electron microscopy has shown thrips carrying pollen grains adhering to their backs, and their fringed wings are perfectly capable of allowing them to fly from plant to plant.[
]
Damage to plants
Thrips can cause damage 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 host. Family 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 ante ...
in particular is notorious for members with broad host ranges, and the majority of pest thrips come from this family. For example, ''Thrips tabaci
''Thrips tabaci'' is a species of very small insect in the genus ''Thrips'' in the order Thysanoptera. It is commonly known as the onion thrips, the potato thrips, the tobacco thrips or the cotton seedling thrips. It is an agricultural pest that ...
'' damages crops of onion
An onion (''Allium cepa'' L., from Latin ''cepa'' meaning "onion"), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus ''Allium''. The shallot is a botanical variety of the onion ...
s, potato
The potato is a starchy food, a tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial in the nightshade family Solanaceae.
Wild potato species can be found from the southern Unit ...
es, tobacco
Tobacco is the common name of several plants in the genus '' Nicotiana'' of the family Solanaceae, and the general term for any product prepared from the cured leaves of these plants. More than 70 species of tobacco are known, but the ...
, and cotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus ''Gossypium'' in the mallow family Malvaceae. The fiber is almost pure cellulose, and can contain minor perce ...
.
Some species of thrips create galls, almost always in leaf tissue. These may occur as curls, rolls or folds, or as alterations to the expansion of tissues causing distortion to leaf blades. More complex examples cause rosettes, pouches and horns. Most of these species occur in the tropics and sub-tropics, and the structures of the galls are diagnostic of the species involved. A radiation of thrips species seems to have taken place on ''Acacia
''Acacia'', commonly known as the wattles or acacias, is a large genus of shrubs and trees in the subfamily Mimosoideae of the pea family Fabaceae. Initially, it comprised a group of plant species native to Africa and Australasia. The genus na ...
'' trees in Australia; some of these species cause galls in the petioles, sometimes fixing two leaf stalks together, while other species live in every available crevice in the bark. In ''Casuarina
''Casuarina'' is a genus of 17 tree species in the family Casuarinaceae, native to Australia, the Indian subcontinent, southeast Asia, islands of the western Pacific Ocean, and eastern Africa. It was once treated as the sole genus in the fami ...
'' in the same country, some species have invaded stems, creating long-lasting woody galls.
Social behaviour
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 In Australia, aggregations of male common blossom thrips have been observed on the petals of ''Hibiscus rosa-sinensis
''Hibiscus rosa-sinensis'', known colloquially as Chinese hibiscus, China rose, Hawaiian hibiscus, rose mallow and shoeblack plant, is a species of tropical hibiscus, a flowering plant in the Hibisceae Tribe (biology), tribe of the family (biol ...
'' and ''Gossypium hirsutum
''Gossypium hirsutum'', also known as upland cotton or Mexican cotton, is the most widely planted species of cotton in the world. Globally, about 90% of all cotton production is of cultivars derived from this species. In the United States, the wo ...
''; females were attracted to these groups so it seems likely that the males were producing pheromone
A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
s.
In the phlaeothripids that feed on fungi, males compete
Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, indivi ...
to protect and mate with females, and then defend the egg-mass. Males fight by flicking their rivals away with their abdomen, and may kill with their foretarsal teeth. Small males may sneak in to mate while the larger males are busy fighting. In the Merothripidae and in the Aeolothripidae, males are again polymorphic with large and small forms, and probably also compete for mates, so the strategy may well be ancestral among the Thysanoptera.
Many thrips form galls on plants when feeding or laying their eggs. Some of the gall-forming Phlaeothripidae
Phlaeothripidae is a family of thrips with hundreds of genera. They are the only extant family of the suborder Tubulifera, alongside the extinct family Rohrthripidae and are themselves ordered into two subfamilies, the Idolothripinae with 80 g ...
, such as genera ''Kladothrips
''Kladothrips'' is a genus of Australian gall thrips. It is notable for including some of the few organisms outside of Hymenoptera that exhibit eusociality.
Diversity
The following species of ''Kladothrips'' are recognized:
*''Kladothrips acaci ...
'' and '' Oncothrips'', form eusocial
Eusociality (from Greek εὖ ''eu'' "good" and social), the highest level of organization of sociality, is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping gen ...
groups similar to ant
Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of ...
colonies, with reproductive queens
Queens is a borough of New York City, coextensive with Queens County, in the U.S. state of New York. Located on Long Island, it is the largest New York City borough by area. It is bordered by the borough of Brooklyn at the western tip of Long ...
and nonreproductive soldier castes.
Flight
Most insects create lift by the stiff-winged mechanism of insect flight
Insects are the only group of invertebrates that have evolved wings and flight. Insects first flew in the Carboniferous, some 350 to 400 million years ago, making them the first animals to evolve flight. Wings may have evolved from appenda ...
with steady state
In systems theory, a system or a process is in a steady state if the variables (called state variables) which define the behavior of the system or the process are unchanging in time. In continuous time, this means that for those properties ''p' ...
aerodynamics
Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dy ...
; this creates a leading edge
The leading edge of an airfoil surface such as a wing is its foremost edge and is therefore the part which first meets the oncoming air.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 305. Aviation Supplies & Academics, ...
vortex
In fluid dynamics, a vortex ( : vortices or vortexes) is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices form in stirred fluids, and may be observed in smoke rings, whirlpools in th ...
continuously as the wing
A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expres ...
moves. The feathery wings of thrips, however, generate lift by clap and fling, a mechanism discovered by the Danish zoologist Torkel Weis-Fogh
Torkel Weis-Fogh (25 March 1922 – 13 November 1975) was a Danish zoologist and Professor at the University of Cambridge and the University of Copenhagen. He is best known for his contributions to the understanding of insect flight, especially ...
in 1973. In the clap part of the cycle, the wings approach each other over the insect's back, creating a circulation of air which sets up vortices and generates useful forces on the wings. The leading edges of the wings touch, and the wings rotate around their leading edges, bringing them together in the "clap". The wings close, expelling air from between them, giving more useful thrust. The wings rotate around their trailing edges to begin the "fling", creating useful forces. The leading edges move apart, making air rush in between them and setting up new vortices, generating more force on the wings. The trailing edge vortices, however, cancel each other out with opposing flows. Weis-Fogh suggested that this cancellation might help the circulation of air to grow more rapidly, by shutting down the Wagner effect which would otherwise counteract the growth of the circulation.
Clap and fling flight mechanism after Sane 2003">
File:Clap and Fling 1- clap 1.svg, Clap 1: wings close over back
File:Clap and Fling 2- clap 2.svg, Clap 2: leading edges touch, wing rotates around leading edge
The leading edge of an airfoil surface such as a wing is its foremost edge and is therefore the part which first meets the oncoming air.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 305. Aviation Supplies & Academics, ...
, vortices form
File:Clap and Fling 3 - clap 3.svg, Clap 3: trailing edges close, vortices shed, wings close giving thrust
File:Clap and Fling 4- fling 1.svg, Fling 1: wings rotate around trailing edge to fling apart
File:Clap and Fling 5- fling 2.svg, Fling 2: leading edge moves away, air rushes in, increasing lift
File:Clap and Fling 6- fling 3.svg, Fling 3: new vortex forms at leading edge, trailing edge vortices cancel each other, perhaps helping flow to grow faster (Weis-Fogh 1973)
Apart from active flight, thrips, even wingless ones, can also be picked up by winds and transferred long distances. During warm and humid weather, adults may climb to the tips of plants to leap and catch air current. Wind-aided dispersal of species has been recorded over 1600 km of sea between Australia and South Island of New Zealand. It has been suggested that some bird species may also be involved in the dispersal of thrips. Thrips are picked up along with grass in the nests of birds and can be transported by the birds.
A hazard of flight for very small insects such as thrips is the possibility of being trapped by water. Thrips have non-wetting bodies and have the ability to ascend a meniscus
Meniscus may refer to:
*Meniscus (anatomy), crescent-shaped fibrocartilaginous structure that partly divides a joint cavity
*Meniscus (liquid)
The meniscus (plural: ''menisci'', from the Greek for "crescent") is the curve in the upper surface ...
by arching their bodies and working their way head-first and upwards along the water surface in order to escape.
Lifecycle
Thrips lay extremely small eggs, about 0.2 mm long. Females of the suborder Terebrantia
Terebrantia is a suborder of thrips (order Thysanoptera). Order Thysanoptera includes 5,500 species classified into two suborders distinguished by the ovipositor. Terebrantia have a well-developed conical ovipositor, while the Tubulifera do not. ...
cut slits in plant tissue with their ovipositor, and insert their eggs, one per slit. Females of the suborder Tubulifera
Phlaeothripidae is a family of thrips with hundreds of genera. They are the only extant family of the suborder Tubulifera, alongside the extinct family Rohrthripidae and are themselves ordered into two subfamilies, the Idolothripinae with 80 g ...
lay their eggs singly or in small groups on the outside surfaces of plants.
Thrips are hemimetabolous
Hemimetabolism or hemimetaboly, also called incomplete metamorphosis and paurometabolism,McGavin, George C. ''Essential Entomology: An Order-by-Order Introduction''. Oxford: Oxford University Press, 2001. pp. 20. is the mode of development of certa ...
, metamorphosing gradually to the adult form. The first two instar
An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ...
s, called larvae or nymphs, are like small wingless adults (often confused with springtail
Springtails (Collembola) form the largest of the three lineages of modern hexapods that are no longer considered insects (the other two are the Protura and Diplura). Although the three orders are sometimes grouped together in a class called Ento ...
s) without genitalia; these feed on plant tissue. In the Terebrantia, the third and fourth instars, and in the Tubulifera also a fifth instar, are non-feeding resting stages similar to pupa
A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in thei ...
e: in these stages, the body's organs are reshaped, and wing-buds and genitalia are formed.[ The adult stage can be reached in around 8–15 days; adults can live for around 45 days.][ Adults have both winged and wingless forms; in the grass thrips ''Anaphothrips obscurus'', for example, the winged form makes up 90% of the population in spring (in temperate zones), while the wingless form makes up 98% of the population late in the summer.] Thrips can survive the winter as adults or through egg or pupal diapause
In animal dormancy, diapause is the delay in development in response to regular and recurring periods of adverse environmental conditions.Tauber, M.J., Tauber, C.A., Masaki, S. (1986) ''Seasonal Adaptations of Insects''. Oxford University Press I ...
.
Thrips are haplodiploid
Haplodiploidy is a sex-determination system in which males develop from unfertilized eggs and are haploid, and females develop from fertilized eggs and are diploid. Haplodiploidy is sometimes called arrhenotoky.
Haplodiploidy determines the se ...
with haploid males (from unfertilised eggs, as in Hymenoptera
Hymenoptera is a large order (biology), order of insects, comprising the sawfly, sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are Par ...
) and diploid females capable of parthenogenesis
Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and development ...
(reproducing without fertilisation), many species using arrhenotoky
Arrhenotoky (from Greek -τόκος ''-tókos'' "birth of -" + ἄρρην ''árrhēn'' "male person"), also known as arrhenotokous parthenogenesis, is a form of parthenogenesis in which unfertilized eggs develop into males. In most cases, parthe ...
, a few using thelytoky
Thelytoky (from the Greek ''thēlys'' "female" and ''tokos'' "birth") is a type of parthenogenesis in which females are produced from unfertilized eggs, as for example in aphids. Thelytokous parthenogenesis is rare among animals and reported in a ...
. In '' Pezothrips kellyanus'' females hatch from larger eggs than males, possibly because they are more likely to be fertilized. The sex-determining bacterial endosymbiont
An ''endosymbiont'' or ''endobiont'' is any organism that lives within the body or cells of another organism most often, though not always, in a mutualistic relationship.
(The term endosymbiosis is from the Greek: ἔνδον ''endon'' "within ...
''Wolbachia
''Wolbachia'' is a genus of intracellular bacteria that infects mainly arthropod species, including a high proportion of insects, and also some nematodes. It is one of the most common parasitic microbes, and is possibly the most common reproducti ...
'' is a factor that affects the reproductive mode. Several normally bisexual species have become established in the United States with only females present.
Human impact
As pests
Many thrips are pests of commercial crops due to the damage they cause by feeding on developing flowers or vegetables, causing discoloration, deformities, and reduced marketability of the crop. Some thrips serve as vectors for plant diseases, such as tospoviruses. Over 20 plant-infecting viruses are known to be transmitted by thrips, but perversely, less than a dozen of the described species are known to vector tospoviruses. These enveloped viruses are considered among some of the most damaging of emerging plant pathogens around the world, with those vector species having an outsized impact on human agriculture. Virus members include the tomato spotted wilt virus
Transmission and lifespan
TSWV, which is transmitted by thrips, causes serious losses in economically important crops and it is one of the most economically devastating plant viruses in the world. The circulative propagative transmission of T ...
and the impatiens necrotic spot viruses. The western flower thrips, ''Frankliniella occidentalis
The western flower thrips 'Frankliniella occidentalis'' (Pergande)is an invasive pest insect in agriculture. This species of thrips is native to the Southwestern United States but has spread to other continents, including Europe, Australia (whe ...
'', has spread until it now has a worldwide distribution, and is the primary vector of plant diseases caused by tospoviruses. Other viruses that they spread include the genera ''Ilarvirus
''Ilarvirus'' is a genus of positive-strand RNA viruses in the family ''Bromoviridae''. Plants serve as natural hosts. There are 22 species in this genus.
Structure
Viruses in the genus ''Ilarvirus'' are non-enveloped, with icosahedral and quas ...
'', '' (Alpha, Beta, Gamma)carmovirus'', '' Sobemovirus'' and '' Machlomovirus.'' Their small size and predisposition towards enclosed places makes them difficult to detect by phytosanitary inspection
Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomy ...
, while their eggs, laid inside plant tissue, are well-protected from pesticide sprays. When coupled with the increasing globalization
Globalization, or globalisation (Commonwealth English; see spelling differences), is the process of interaction and integration among people, companies, and governments worldwide. The term ''globalization'' first appeared in the early 20t ...
of trade and the growth of greenhouse
A greenhouse (also called a glasshouse, or, if with sufficient heating, a hothouse) is a structure with walls and roof made chiefly of Transparent ceramics, transparent material, such as glass, in which plants requiring regulated climatic condit ...
agriculture, thrips, unsurprisingly, are among the fastest growing group of invasive species in the world. Examples include ''F. occidentalis'', ''Thrips simplex
''Thrips simplex'' is a species of insect in the genus ''Thrips (genus), Thrips'' in the order Thysanoptera. It is commonly known as the gladiolus thrips and infests gladiolus plants as well as various other monocotyledonous plants such as Liliu ...
'', and ''Thrips palmi
''Thrips palmi'' is an insect from the genus ''Thrips'' in the order Thysanoptera. ''.
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
''Frankliniella'' is a genus of thrips belonging to the family Thripidae.
The genus was first described by Karny in 1910.
The genus has cosmopolitan distribution. ''Frankliniella'' species can be quite variable in appearance, making identific ...
'' and ''Limothrips cerealium
''Limothrips'' is a genus of insects belonging to the family 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 ...
'') to "bite" humans under such circumstances. Although no species feed on blood and no known animal disease is transmitted by thrips, some skin irritation has been described.
Management
Thrips develop resistance to insecticides easily and there is constant research on how to control them. This makes thrips ideal as models for testing the effectiveness of new pesticides and methods.
Due to their small sizes and high rates of reproduction, thrips are difficult to control using classical biological control. Suitable predators must be small and slender enough to penetrate the crevices where thrips hide while feeding, and they must also prey extensively on eggs and larvae to be effective. Only two families of parasitoid
In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...
Hymenoptera
Hymenoptera is a large order (biology), order of insects, comprising the sawfly, sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are Par ...
parasitize eggs and larvae, the Eulophidae
The Eulophidae are a large family of hymenopteran insects, with over 4,300 described species in some 300 genera. The family includes the genus '' Elasmus'', which used to be treated as a separate family, "Elasmidae", and is now treated as a s ...
and the Trichogrammatidae
The Trichogrammatidae are a family of 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, with species of '' Megaphragma'' having an adult body length ...
. Other biocontrol agents of adults and larvae include anthocorid bugs of genus ''Orius
The genus ''Orius'' (commonly called minute pirate bug) consists of omnivorous bugs in the family Anthocoridae (pirate bugs). Adults are 2–5 mm long and feed mostly on smaller insects, larva and eggs, such as spider mites, thrips, ...
'', and phytoseiid
The Phytoseiidae are 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. Because of their usefulness as biological control agents, interest in Phytoseiidae has ...
mites. Biological insecticides such as the fungi '' Beauveria bassiana'' and '' Verticillium lecanii'' can kill thrips at all life-cycle stages. Insecticidal soap Insecticidal soap is used to control many plant insect pests. Soap has been used for more than 200 years as an insect control. Because insecticidal soap works on direct contact with pests via the disruption of cell membranes when the insect is pen ...
spray is effective against thrips. It is commercially available or can be made of certain types of household soap. Scientists in Japan report that significant reductions in larva and adult melon thrips occur when plants are illuminated with red light.
References
External links
Thrips of the World checklist
Thrips species wiki
Thrips images from the "Pests and Diseases Image Library (PaDIL)" of Australia
* ttp://keys.lucidcentral.org/keys/v3/thrips_of_california/Thrips_of_California.html University of California Thrips Identification* CISR: Center for Invasive Species Research Fact Sheets
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Avocado Thrips
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* Thrips links on the UF / IFAS Featured Creatures Web site
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schultzei'', common blossom thrips
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{{Authority control
Agricultural pest insects
Extant Permian first appearances
Taxa named by Alexander Henry Haliday
Condylognatha