''Chirosia betuleti'' is a species of

fly Flies are insects of the Order (biology), order Diptera, the name being derived from the Ancient Greek, Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwing ...

, which causes knotting gall in ferns. The

gall Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissues, similar to be ...

develops in the terminal shoots of ferns, such as broad buckler fern (''

Dryopteris dilatata ''Dryopteris dilatata'', the broad buckler-fern, is a robust species of deciduous or semievergreen fern in the family Dryopteridaceae, native to Europe, particularly western and central Europe. In southern Europe, it is mostly found in mountainou ...

''), male fern (''

Dryopteris filix-mas ''Dryopteris filix-mas'', the male fern, is a common fern of the temperate Northern Hemisphere, native to much of Europe, Asia, and North America. It favours damp shaded areas in the understory of woodlands, but also shady places on hedge-banks, ...

''), lady fern (''

Athyrium filix-femina ''Athyrium filix-femina'', the lady fern or common lady-fern, is a large, feathery species of fern native to temperate Asia, Europe, North Africa, Canada and the USA. It is often abundant (one of the more common ferns) in damp, shady woodland env ...

''), and ostrich fern (''

Matteuccia ''Matteuccia'' is a genus of ferns with one species: ''Matteuccia struthiopteris'' ( common names ostrich fern, fiddlehead fern, or shuttlecock fern). The species epithet ''struthiopteris'' comes from Ancient Greek words () "ostrich" and () "fe ...

struthiopteris)''.Stubbs, F. B. Edit. (1986) ''Provisional Keys to British Plant Galls''. Pub. Brit Plant Gall Soc. ., p. 80Redfern, Margaret & Shirley, Peter (2002). ''British Plant Galls. Identification of galls on plants & fungi.'' AIDGAP. Shrewsbury : Field Studies Council. , p. 288BioStor
Retrieved: 2011-07-28

The physical appearance of the galls

The fly larva mines the leaves and stems of the fern's frond at the apex. The tip of the frond rolls upwards into a loose, obvious knot or mop-head structure involving many pinnae; inside, a white larva mines along the rachis, eating the

trichomes Trichomes (); ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a plant ...

, causing it to coil. Usually, only one larva is present in the leaf tip, sometimes two. An elongated white egg shell is visible at the centre of the mass.Leaf and Stem Mines
Retrieved : 2011-07-28

Lifecycle

Eggs are laid in the unfurling fronds and the hatched larvae feed on the trichomes in the groove of the rachis, causing the frond to curl inwards. The pupae drop from the gall and remain from autumn and winter to emerge in the spring. Galling rates up to nine fronds in 13 on a single plant have been noted.

Distribution

The knotting gall is found in Cornwall, Wiltshire, Worcester, Hants, Norfolk, Warwickshire, Berkshire, Cardiganshire, Cheshire, Denbighshire, East Norfolk, Suffolk, Easterness, Elgin, Flintshire, North Ayrshire, Herefordshire, Merionethshire, Perth, Yorkshire, Montgomeryshire, Lincolnshire, Somerset, Oxfordshire, Shropshire, Devon, Hampshire, Yorkshire, Stafford, Surrey, Gloucestershire, Kent, Suffolk, and Worcestershire. As shown, the knotting gall has been recorded throughout the United Kingdom, in the Netherlands, the Czech Republic, Denmark, Finland, France, Germany, Italy, Norway, Poland, Russia – north and north-west, Slovakia, Spain, and Sweden.

Parasitoids

Braconid The Braconidae are a family of parasitoid wasps. After the closely related Ichneumonidae, braconids make up the second-largest family in the order Hymenoptera, with about 17,000 recognized species and many thousands more undescribed. One analysis ...

wasps of the genus ''Aphaereta'' and eulophid wasps of the genera ''

Dimmockia ''Dimmockia'' is a genus of hymenopteran insects of the family 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 ...

'' and ''

Elachertus ''Elachertus'' is a genus of hymenopteran insects of the family 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 ...

'' have been identified as

parasitoids In evolutionary ecology, a parasitoid is an organism that lives in close association with its host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionary strategies within parasi ...

of ''C. betuleti''.

The physical appearance of the galls

Lifecycle

Distribution

Parasitoids

References

Further reading