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Thysanoptera THRIPS Life   Insecta

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Fruit Pests Groups Insecta Insect orders Nearctic Insecta other North American Invasives Thrips

Kinds

Aeolothripidae Heterothripidae Idolothripinae Merothripidae Phlaeothripidae Thripidae

Index

They are abundant in the tropical and temperate regions of the world and approximately 5,000 species have been described. Thrips have an economic importance, for some species may transmit plant viruses, reduce productivity of plant, reduce flowers and fruits, or skelatonize (eat) plant leaves. On the other hand, a few species prey on destructive mites and scale insects, and a number may aid in the pollination of flowers and, indirectly, in the formation of leaf mold. The larvae of thrips tend to be colored brightly the adults range from whitish to brown or black. Adults have extensible bladders on the tarsi of the legs, thus they are also commonly referred to as bladder feet. The order Thysanoptera is divided into two distinct suborders. The suborder Terebrantia contains four families and the suborder Tubulifera contains two.

The order is divided based on the presence or absence of an ovipositor (egg laying tube). The females of the Terebrantia have retained the ovipositor whereas the females of the Tubulifera have undergone a secondary loss with the abdominal (most posterior) segment fusing into a tube. Fossil thrips are known from only as far back in time as the Jurassic period, making them relatively modern as far as insects are concerned.

Identification Thrips have several defining characteristics that one may look for.

• asymmetrical mouthparts with right mandible lost
• two or three quiescent, pre-imaginal instars
• pretarsus with protrusible "bladder", which balloons out as leg makes contact with the ground.
• wing linear with long marginal setae

The principle morphological feature to look for is the asymmetrical mouth. In which the left mandible appears much larger than the vestigial right.

Photographs

[Species: E. americanus.]	[Species: Frankliniella fusca]	[Species: Frankliniella trictici]	[Species: Gynaikothrips ficorum]

Thysanoptera damage	Thysanoptera life stages	Thysanoptera	Thysanoptera damage	Order: Thysanoptera Photo Copyright Tree of Life

[Species: Limothrips cerealium]	Thysanoptera damage	Thysanopteran female	Thysanopteran setae
Order: Thysanoptera Photo Copyright Rhodes University	Species:Franklinothrips vespiformis Photo Copyright Mark S Hoddle	Thrips Life Cycle Photo Copyright Mark S Hoddle	Order: Thysanoptera Photo Copyright Bugpeople
Family: Phlaeothripidae Photo Copyright Honey Bee Lab	Species:Scirtothrips perseae Photo Copyright Mark S. Hoddle	Species:Frankliniella occidentalis Photo Copyright Mark S Hoddle	Species:Heliothrips haemorrhoidalis Photo Copyright Mark S Hoddle

Geographic distribution Thrip's occurances are diverse in distribution. Families can be present on several continents. Aeolothripids are widely distributed and occur in Europe, Asia, Africa, Hawaii, and North America. However, the only common species of Merothripidae, Merothripidae morgani, is endemic to the eastern United States. Heterothripids occur mainly in North America. Species in the genus Oligothrips occur mainly in Oregon and California. However, the genus Heterothrips ia widely distributed across the continent. Thripidae is another family that is widely distributed occurring in many temperate and tropical regions. Phlaeothipids occur in both Australia and North America.

Natural history The development of thrips takes place in the egg, in two larval stages, during which all the immature feeding occurs, and in one, two, or three pupal stages in which no feeding has been observed. Although the changes that occur in pupae of Thysanoptera resemble those that occur in insects that undergo complete metamorphosis, thrips belong to a group of insects that usually undergo simple metamorphosis. Thrips main reproductive strategy is sexual reproduction. Parthenogenesis is known but rare. Also, ovoviparity can occur in some members of the order Tubulifera. The males are shorter lived than females, therefore, mating often takes place early in the life span. Eggs are elongated, oval to kidney shaped, faintly to distinctly sculptured, and, as is the case in other minute insects, are proportionately large, often occupying two or three abdominal segments of the female before laying.

Eggs are inserted into tissues of living plants, pushed under bark, inserted in or between flowers and leaf sheaths or glued onto leaf or bark surfaces, etc. The strategy used to lay eggs depends on the species and hence the presence or absence and the shape of the ovipositor. Eggs may take as many as sixteen days to hatch. Although similar in overall form to the adult, the larvae of thrips are weaker and simpler in structure. The long anal bristles characteristic of larvae may hold droplets of excreted liquid that are deposited on leaf surfaces. The first stage is short (a few days); the second may last up to many months when estivation or hibernation occurs. Depending on the family, the larvae may transform directly into the prepupal form or may pass through an abbreviated intermediate form called the primpupa.

Click here to see the Thrip life cycle.

The prepupal stage is of short duration (a few hours to several days) and gives rise to the final pupal stage, of short or long duration, that eventually produces the adult.

Pupation takes place in the ground in earthen cells, in cocoons, or on a host plant. Some thrips, for example, the ear thrips, have only one generation per year; others such as the onion thrips may have several generations each growing season.

In regions having winter cold, thrips hibernate as adults or immature forms in detritus, hollow stems, or in the ground. Those that perish with the cold are replaced each year by spring migrants from warmer areas. In the tropics many thrips exhibit seasonal fluctuations, being more active in the wet than in the dry seasons. Some thrips are sensitive to relative humidity. Larvae are generally found in shady locations, on the underside of leaves or branches. Adults occasionally occur on the upper side of leaves in bright light. Most thrips rest tightly against leaf veins or in crevices. They are primarily active during the daylight hours. Thrips are preyed upon by many insects (including other thrips), mites, birds, salamanders, and lizards. Heavy rains, winds, and dust are, however, probably as destructive to thrips as are predators.

How to encounter Thrips may be found in flowers, foliage, fruits, bark, fungi, and in debris. Aeolothripids occur on various plants but are particularly common on the flower heads of clover. Merothripids occur under bark, in debris, and in fungi. Heterothripids can be found mainly in trees (e.g. oak, willow), in flowers (e.g. azalea, jack-in-the-pulpit) or in the buds of the wild grape. Members of the family Thripidae can be found attacking pears, plums, cherries,onions,tobacco, beans, or grains. They are a large and diverse group and different species target different portions of the plant. The presence of dark colored spots of excreta adjacent to light colored feeding zones are some typical signs of thrips damage. They may be collected by a variety of means. For example, species found on vegetation may be collected by sweeping.

Links to other sites

• NC State AgNIC Systematic Entomology
• HYPP Zoology page on Thysanoptera
• For natural history information about Thysanoptera, visit John R. Meyer's site at NC State University, Department of Entomology.

• Borror J., Triplehorn C. A., and Johnson N. An Introduction to the study of insects. Sixth Edition. Order Thysanoptera Saundera College Publishing Chicago, IL 350-356
• www.britannica.com
• www.earthlife.net

Thanks to Sabina Gupta, Denise Lim, and Dr. John Pickering for technical and web support in developing this page.