Barkflies, booklice or psocids
 
Barkflies, also known as barklice, booklice or psocids, are insects belonging to the order Psocoptera.  Psocids are an ancient order of primitive exopterygote insects, related to the lice and true bugs. They are small and soft-bodied, 1-7mm long, with prominent eyes, thin legs and long antennae.  Some species are wingless, while some of the winged species have wings with dark markings on otherwise transparent wings. At rest, the wings are held tent-like over the body.  Barklice are mostly a drab greyish brown colour, but the common Valenzuela flavidus has a yellow abdomen. As a group they are poorly recorded, because although often abundant, they are small and hard to identify, and not any threat to cultivated plants.
 
Species in Britain and Ireland
There are about 100 species of psocids that have been recorded in Britain and Ireland.  Of these more than 30 are normally found inside buildings, where they can infest dry foodstuffs in kitchens.  The name ‘booklice’ given to indoor psocids comes from an association with older books which used starch-based or animal based glues in the bindings.   The outdoor species are known as barkflies or barklice.  They can be found on or under the bark and foliage of many tree and shrubs, including evergreen species.  Other species live in leaf litter or the surface layers of the soil. Even winged species seem more prone to running away than flying when disturbed. The barkfly recording scheme lists 12 species as common in Britain and Ireland, including more than one species in the genera Ectopsocus, Peripsocus and Valenzuela.  Jennifer Owen recorded 18 species of barkflies using malaise traps in her Leicester garden, with Graphopsocus cruciatus, Ectopsocus petersi and Ectopsocus briggsi being the commonest.
 
 
 
Left: Graphopsocus cruciatus    Centre: Ectopsocus petersi   Right: Psocid nymph - note the externally growing wings.
 
Biology
Barkflies feed mainly on fungi, algae, lichen and other microflora.  They can be abundant on foliage that has a coating of sooty moulds following infestation with aphids or another sap-sucking insect. Most species overwinter as eggs but some do so as adults and may become active on mild sunny days.  The peak period for adult barkflies is late summer.
 
Life cycle
Barkflies deposit their eggs in crevices in bark or other suitable substrates.  The eggs are often covered with faecal matter or a sheet of silk threads.  The young nymphs are similar in appearance to the adults, with wing pads developing in the later nymphal instars.  Most garden barkflies have one generation a year but some species have two. Indoor booklice can breed throughout the year and can have many generations in a warm kitchen.
 
Role of barkflies in gardens
Barkflies form part of a healthy garden ecosystem. The abundance of some species means they are likely to be important prey items for many predatory insects and spiders, as well as some birds such as tits.
 
Other sources of information
 
Website
Website of the National Barkfly Recording Scheme
 
Book
New, T.R. (2005) Handbooks for the Identification of British Insects Vol 1 part 7 Psocids, Psocoptera (booklice, barklice). Royal Entomological Society
 
 
Page text drafted by Andrew Halstead, reviewed by Andrew Salisbury, compiled by Steve Head
 
 
Barkflies, booklice or psocids
 
Barkflies, also known as barklice, booklice or psocids, are insects belonging to the order Psocoptera.  Psocids are an ancient order of primitive exopterygote insects, related to the lice and true bugs. They are small and soft-bodied, 1-7mm long, with prominent eyes, thin legs and long antennae.  Some species are wingless, while some of the winged species have wings with dark markings on otherwise transparent wings. At rest, the wings are held tent-like over the body.  Barklice are mostly a drab greyish brown colour, but the common Valenzuela flavidus has a yellow abdomen. As a group they are poorly recorded, because although often abundant, they are small and hard to identify, and not any threat to cultivated plants.
 
Species in Britain and Ireland
There are about 100 species of psocids that have been recorded in Britain and Ireland.  Of these more than 30 are normally found inside buildings, where they can infest dry foodstuffs in kitchens.  The name ‘booklice’ given to indoor psocids comes from an association with older books which used starch-based or animal based glues in the bindings.   The outdoor species are known as barkflies or barklice.  They can be found on or under the bark and foliage of many tree and shrubs, including evergreen species.  Other species live in leaf litter or the surface layers of the soil. Even winged species seem more prone to running away than flying when disturbed. The barkfly recording scheme lists 12 species as common in Britain and Ireland, including more than one species in the genera Ectopsocus, Peripsocus and Valenzuela.  Jennifer Owen recorded 18 species of barkflies using malaise traps in her Leicester garden, with Graphopsocus cruciatus, Ectopsocus petersi and Ectopsocus briggsi being the commonest.
 
 
 
Biology
Barkflies feed mainly on fungi, algae, lichen and other microflora.  They can be abundant on foliage that has a coating of sooty moulds following infestation with aphids or another sap-sucking insect. Most species overwinter as eggs but some do so as adults and may become active on mild sunny days.  The peak period for adult barkflies is late summer.
 
Life cycle
Barkflies deposit their eggs in crevices in bark or other suitable substrates.  The eggs are often covered with faecal matter or a sheet of silk threads.  The young nymphs are similar in appearance to the adults, with wing pads developing in the later nymphal instars.  Most garden barkflies have one generation a year but some species have two. Indoor booklice can breed throughout the year and can have many generations in a warm kitchen.
 
Role of barkflies in gardens
Barkflies form part of a healthy garden ecosystem. The abundance of some species means they are likely to be important prey items for many predatory insects and spiders, as well as some birds such as tits.
 
Other sources of information
 
Website
Website of the National Barkfly Recording Scheme
 
Book
New, T.R. (2005) Handbooks for the Identification of British Insects Vol 1 part 7 Psocids, Psocoptera (booklice, barklice). Royal Entomological Society
 
Page text drafted by Andrew Halstead, reviewed by Andrew Salisbury, compiled by Steve Head
 
 
Double click to edit 
Top left: Graphopsocus cruciatus    Right: Ectopsocus petersi   
 
Left: Psocid nymph - note the externally growing wings.
 
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