is pollinated by Thrips setipennis''.
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, their diet often being supplemented with
pollen. Other species are primitively
eusocial and form plant
galls, while 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.
Akainothrips francisi of Australia is a parasite within the colonies of another thrips species
Dunatothrips aneurae that makes silken nests or domiciles on
Acacia trees. A number of thrips in the subfamily Phlaeothripinae that specialize on
Acacia hosts produce silk with which they glue together phyllodes to form domiciles inside which their semi-social colonies live.
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, are also predators, and are considered beneficial in the management of pests like the
codling moths. 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 leaves rolled up by
Hoplandrothrips (
Phlaeothripidae) damage 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. Amber fossils of
Gymnopollisthrips from the
Early Cretaceous show them to be coated in
Cycadopites-like pollen.
Scirtothrips dorsalis carries pollen of commercially important
chili peppers. 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, 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 and
M. variabilis. The genus
Cycadothrips is a specialist pollinator of
cycads, which are normally wind pollinated but some species of
Macrozamia are able to attract thrips to male cones at some times and repel them so that they move to female cones. Thrips are likewise the primary pollinators of heathers in the family
Ericaceae, 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 allow them to fly from plant to plant. 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 in particular is notorious for members with broad host ranges, and the majority of pest thrips come from this family. For example,
Thrips tabaci damages crops of
onions,
potatoes,
tobacco, and
cotton. colonies of
Kladothrips live in
galls induced on
Acacia trees. 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 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 trees in the same country, some thrips 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 and
Gossypium hirsutum; females were attracted to these groups so it seems likely that the males were producing
pheromones. In the phlaeothripids that feed on fungi, males
compete 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, such as genera
Kladothrips and
Oncothrips, form
eusocial groups similar to
ant colonies, with reproductive
queens and nonreproductive soldier castes.
Flight lands on
ladybird beetle eggs, getting stuck. It took an hour to unstick its wings and fly away. Most insects create lift by the stiff-winged mechanism of
insect flight with
steady state aerodynamics; this creates a
leading edge vortex continuously as the
wing moves. The feathery wings of thrips, however, generate lift by
clap and fling, a mechanism discovered by the Danish zoologist
Torkel Weis-Fogh 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. 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, 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 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. 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 by arching their bodies and working their way head-first and upwards along the water surface in order to escape.
Life cycle Thrips lay extremely small eggs, about 0.2 mm long. Females of the suborder
Terebrantia cut slits in plant tissue with their ovipositor, and insert their eggs, one per slit. Females of the suborder
Tubulifera lay their eggs singly or in small groups on the outside surfaces of plants. Some thrips such as
Elaphothrips tuberculatus are known to be facultatively ovoviviparous, retaining the eggs internally and giving birth to male offspring. Females in many species guard the eggs against cannibalism by other females as well as predators. Thrips are
hemimetabolous, metamorphosing gradually to the adult form. The first two
instars, called larvae or nymphs, are like small wingless adults (often confused with
springtails) 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
pupae: 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. Thrips can survive the winter as adults or through egg or pupal
diapause. In
Pezothrips kellyanus females hatch from larger eggs than males, possibly because they are more likely to be fertilized. The sex-determining bacterial
endosymbiont Wolbachia 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==