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Thrips
Thrips, which are sometimes called thunder flies, are insects belonging to the order Thysanoptera. They are tiny, narrow bodied insects 1-3 mm long. The legs and antennae are short. They often appear to be wingless since the wings are held flat over the back of the insect and are not easily seen. The two pairs of wings have a narrow strap-like form, with a fringe of long fine hairs on the hind edge, at rest folded back over the body.
In some species the wings have dark markings, giving the thrips a banded appearance. Most thrips are black or blackish brown in colour when adult but the larval stages are usually cream or pale yellowish orange. Note that the name ‘thrips’ is both a singular and plural word (like "sheep"); writing ‘a thrip’ is incorrect.
Species in Britain and Ireland
There are about 160 species of thrips recorded in Britain and Ireland, some of which are introduced species that are found only in glasshouses. Thrips sometimes swarm in huge numbers, especially on humid days in late summer. It is this activity that gives them the name of ‘thunder flies’. The species responsible is usually the cereal thrips, Limothrips cerealium, which migrates away from cereal fields as the plants dry up at harvest time.
Inevitably the species that damage plants have received most attention in gardens. Some common species include gladiolus thrips Thrips simplex, privet/lilac thrips Dendrothrips ornatus, pea thrip Kakothrips pisivorus and onion/leek thrips Thrips tabaci. Thrips which feed on a wide range of plants in greenhouses and on house plants include western flower thrips, Frankliniella occidentalis and glasshouse thrips, Heliothrips haemorrhoidalis. The last mentioned has recently become a problem on some outdoor plants in central London, especially on Viburnum tinus. Most thrips are associated with plants but some live in leaf litter.
Biology
Some thrips are fungal feeders or predators of other small insects and mites but most UK species feed by sucking sap from plants, or they feed on pollen grains in flowers. Some species can damage garden and glasshouse plants, but equaly some thrips can serve as pollinators.
Life cycle
Thrips’ larvae have a shape similar to the adult insects but they lack wings. When the larvae are fully fed, the larvae pass through non-feeding pre-pupal and pupal stages before the adult insect emerges. The pre-pupal and pupal stages, during which the wings and other adult features develop, may be on foliage or flowers alongside the larvae, or they can take place in the soil. Some thrips overwinter as adults, while others do so in one of the earlier stages.
Role of thrips in gardens
The majority of thrips cause no significant damage to plants. Flower-dwelling thrips may play some part in the pollination process when they crawl around in flowers or transfer to other blooms.
Thrips cause a silvery white discoloration of the foliage and may also damage developing flowers.
Above: Left: Grain thrips Limothrips cerealium Centre: Thrips tabaci on left and Frankliniella occidentalis on right. Right: Unidentified thrips nymph.
Left: Thunderflies massed on a daisy head
Thrips damage. Left: Glasshouse thrips Heliothrips haemorrhoidalis on Rhododendron sp. Privet thrips Dendrothrips ornatus on lilac Syringa sp.
Other sources of information
Website
Dr. Manfred Ulitzka’s website on Thysanoptera
RHS page on thrips
Book
Kirk, W. D. J. (1996) Naturalists’ Handbooks 25 Thrips. Richmond Publishing
Page text drafted by Andrew Halstead, reviewed by Andrew Salisbury, compiled by Steve Head
Thrips
Thrips, which are sometimes called thunder flies, are insects belonging to the order Thysanoptera. They are tiny, narrow bodied insects 1-3 mm long. The legs and antennae are short. They often appear to be wingless since the wings are held flat over the back of the insect and are not easily seen. The two pairs of wings have a narrow strap-like form, with a fringe of long fine hairs on the hind edge, at rest folded back over the body.
In some species the wings have dark markings, giving the thrips a banded appearance. Most thrips are black or blackish brown in colour when adult but the larval stages are usually cream or pale yellowish orange. Note that the name ‘thrips’ is both a singular and plural word (like "sheep"); writing ‘a thrip’ is incorrect.
Species in Britain and Ireland
There are about 160 species of thrips recorded in Britain and Ireland, some of which are introduced species that are found only in glasshouses. Thrips sometimes swarm in huge numbers, especially on humid days in late summer. It is this activity that gives them the name of ‘thunder flies’. The species responsible is usually the cereal thrips, Limothrips cerealium, which migrates away from cereal fields as the plants dry up at harvest time.
Inevitably the species that damage plants have received most attention in gardens. Some common species include gladiolus thrips Thrips simplex, privet/lilac thrips Dendrothrips ornatus, pea thrip Kakothrips pisivorus and onion/leek thrips Thrips tabaci. Thrips which feed on a wide range of plants in greenhouses and on house plants include western flower thrips, Frankliniella occidentalis and glasshouse thrips, Heliothrips haemorrhoidalis. The last mentioned has recently become a problem on some outdoor plants in central London, especially on Viburnum tinus. Most thrips are associated with plants but some live in leaf litter.
Above: Left: Grain thrips Limothrips cerealium Right: Thrips tabaci on left and Frankliniella occidentalis on right.
Below: Left: Unidentified thrips nymph Right: Thunderflies massed on a head of ox-eye daisy Leucanthemum vulgare
Biology
Some thrips are fungal feeders or predators of other small insects and mites but most UK species feed by sucking sap from plants, or they feed on pollen grains in flowers. Some species can damage garden and glasshouse plants, but equaly some thrips can serve as pollinators.
Life cycle
Thrips’ larvae have a shape similar to the adult insects but they lack wings. When the larvae are fully fed, the larvae pass through non-feeding pre-pupal and pupal stages before the adult insect emerges. The pre-pupal and pupal stages, during which the wings and other adult features develop, may be on foliage or flowers alongside the larvae, or they can take place in the soil. Some thrips overwinter as adults, while others do so in one of the earlier stages.
Role of thrips in gardens
The majority of thrips cause no significant damage to plants. Flower-dwelling thrips may play some part in the pollination process when they crawl around in flowers or transfer to other blooms.
Thrips cause a silvery white discoloration of the foliage and may also damage developing flowers.
Thrips damage. Left: Glasshouse thrips Heliothrips haemorrhoidalis on Rhododendron sp. Privet thrips Dendrothrips ornatus on lilac Syringa sp.
Other sources of information
Website
Book
Kirk, W. D. J. (1996) Naturalists’ Handbooks 25 Thrips. Richmond Publishing
Page text drafted by Andrew Halstead, reviewed by Andrew Salisbury, compiled by Steve Head
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