Bedfordshire Scale Insects

A brief guide to the scale insects (Hemiptera: Coccoidea) recorded in Bedfordshire

Photo of Phenacoccus aceris to aid identification Young female Parthenolecanium corni
Scale insects are plant-sap feeding insects, closely related to the aphids, whiteflies and jumping plant lice or psyllids. They are among the most highly specialised of all plant parasites and feed on all parts of the plant including the roots, stems, leaves, buds and fruit. The adult females do not look like typical insects as they retain the immature external morphology at sexual maturity. Adult males, however, resemble small flies but never feed and die within a day or two of emergence.

Twenty-two species of scale insect belonging to six families have been recorded in Bedfordshire; the majority collected by the author between 1992-5 when he lived in Luton (collection details will be published in a separate article). Fourteen of the species recorded in Beds are native, two are naturalized introductions, and six are introduced species established on indoor plantings. This may, however, represent only half of the species that are actually present in the county. For comparison, the author has recently recorded 35 native, 4 naturalized introductions and 24 introduced species established on indoor plantings in Yorkshire. Although Yorkshire covers a much larger area, it is located further north where a lower number of species would be expected to occur.

Exotic scale insects are regularly dispersed between countries as a consequence of trade and are one of the most successful arthropod groups in terms of invading new geographical areas. Climate change also appears to be having an influence on the distribution of scale insects within Europe, as species once restricted to the Mediterranean are expanding their range into more northerly latitudes. Several exotic species have appeared in Greater London in recent years and it is probably just a matter of time before they expand their range northwards to Bedfordshire.

Under-recording of native scale insect species in Bedfordshire and the potential for the introduction of exotic species means that there is plenty of scope for recording species new to the county or even the country. Unfortunately the lack of easily accessible literature on scale insects can be a deterrent to their study so brief descriptions and photographs of all the scale insect species recorded in the county so far are provided below. Scale insects are found by careful examination of plant material and may be observed throughout the year on woody hosts. I hope that this information will encourage the recording of this fascinating group of insects as some of the common and/or most distinctive species can be identified in the field. Positive identification of most species, however, requires microscopic examination of slide mounted adult females and it is always advisable to retain voucher specimens. I would be delighted to receive any samples of scale insects and assist with their identification.

NATIVE AND INTRODUCED NATURALIZED SPECIES

PSEUDOCOCCIDAE Mealybugs

Photo of Phenacoccus aceris to aid identification Phenacoccus aceris ovisac
Photo of Phenacoccus aceris to aid identification Phenacoccus aceris adult female
Polyphagous tree mealybug Phenacoccus aceris
Adult female oval, greenish yellow, covered in white to grey mealy wax, with 18 pairs of short marginal wax filaments; up to 4.3 mm long. This species occurs widely in Britain and is locally common. It is broadly polyphagous on woody plants and an occasional pest of ornamental and fruit trees. In Beds it has been found in Dunstable Downs, Luton, Luton Hoo and Sandy on hawthorn, ivy and sycamore.

COCCIDAE Soft scales

Photo of Eulecanium douglasi to aid identification Eulecanium douglasi adult female
Current soft scale Eulecanium douglasi
Adult female, oval, convex, anteriorly rounded, posteriorly flattened, yellowish-brown to dark brown, shiny; up to 9.0 mm long; it is highly variable depending on the host species. This species is rarely recorded in Britain. It is polyphagous on woody plants and in Beds it has been found in Luton on a plum tree.

Photo of Eulecanium tiliae to aid identification Eulecanium tiliae mature adult female
Photo of Eulecanium tiliae to aid identification Eulecanium tiliae young adult female
Nut scale Eulecanium tiliae
Adult female, oval, strongly convex, yellowish-brown to dark brown, shiny; up to 6.5 mm long. This species is widespread and locally common in Britain. It is broadly polyphagous on woody plants, particularly on Rosaceae, and occasionally enormous populations develop that damage woody ornamentals and fruit trees. In Beds it has been found in Dunstable Downs, Luton and Whipsnade; on apple, hawthorn and hornbeam.

Photo of Palaeolecanium bituberculatum to aid identification Palaeolecanium bituberculatum mature adult female
Photo of Palaeolecanium bituberculatum to aid identification Palaeolecanium bituberculatum young adult female
Bituberculate scale Palaeolecanium bituberculatum
Adult females oval, convex, with two pairs of knob-like tubercles, the anterior tubercles much larger and more prominent than the posterior ones, reddish-brown; up to 8 mm long. This species occurs widely in Britain but is rarely recorded. It is polyphagous on woody plants, particularly on Rosaceae. In Beds it has been found in Dunstable Downs, Luton and Sharpenhoe on hawthorn.

Photo of Parthenolecanium corni to aid identification Parthenolecanium corni mature female
Photo of Parthenolecanium corni to aid identification Parthenolecanium corni young female
European fruit lecanium Parthenolecanium corni
Adult females variable in shape, size and colour; usually oval, strongly convex, brown; up to 6.5 mm long. This species is locally common throughout Britain. It is broadly polyphagous and is an important pest of orchard, ornamental and forestry trees. In Beds it has been found in Luton and Sandy; on firethorn and honeysuckle.

Photo of Parthenolecanium pomeranicum to aid identification Parthenolecanium pomeranicum adult female
Yew scale Parthenolecanium pomeranicum
Adult females broadly oval, somewhat tapering at both extremities, strongly convex, shiny dark or reddish brown; up to 5 mm long. This species occurs widely in Britain, but is rarely recorded. It feeds on yew and in Beds it has been found in Sandy and Swiss Cottage.

Photo of Physokermes hemicryphus to aid identification Physokermes hemicryphus adult female
Small spruce bud scale Physokermes hemicryphus
Adult females bud-like, shiny, dark or reddish brown; up to 4.5 mm long. This species occurs widely in Britain, but is rarely recorded. It feeds on spruce and in Beds it has been found in Luton and Luton Hoo.

Photo of Pulvinaria regalis to aid identification Pulvinaria regalis mature female
Photo of Pulvinaria regalis to aid identification Pulvinaria regalis young female
Horse-chestnut scale Pulvinaria regalis
Adult females oval, moderately convex, grey or brown with transverse pale and dark stripes, becoming uniform dark brown with maturity; up to 10 mm long. Ovisac forms beneath female body, which is tilted upwards; ovisac convex, white, about 7 mm long. This species probably originates in Asia, but has become widespread in central and northwest Europe since the 1960s. It is broadly polyphagous on woody plants. It is the most common coccid in urban areas throughout most of Britain but also occurs at low densities in rural areas. In Beds it has been found in Bedford, Bigglesworth, Caddington, Dunstable, Flitwick, Leighton Buzzard, Luton, Luton Hoo, Sandy, Swiss Cottage and Whipsnade; on bay laurel, elm, ivy, horse chestnut, lime, maple and sycamore.

Photo of Pulvinaria vitis to aid identification Pulvinaria vitis male tests
Photo of Pulvinaria vitis to aid identification Pulvinaria vitis adult female with ovisac
Woolly vine scale Pulvinaria vitis
Adult females oval, moderately convex, with transverse wrinkles, dark brown; up to 9 mm long. Ovisac forms beneath female body, which is tilted upwards; ovisac strongly convex, white, about 8 mm long. This species is locally common throughout Britain and feeds on a wide range of woody plants. It is an occasional pest of grapevine, peach and currants. In Beds it has been found in Luton, Luton Hoo and Sandy on hawthorn.

ERIOCOCCIDAE Felt Scales

Photo of Cryptococcus fagisuga to aid identification Cryptococcus fagisuga adult female
Beech scale Cryptococcus fagisuga
Adult female body covered by cream coloured cottony wax secretion; about 1 mm long. It occurs throughout Britain on beech, frequently in very high densities. This species is associated with the transmission of beech bark disease. In Beds it has been found in Luton, Luton Hoo, Sandy, Swiss Cottage and Whipsnade.

Photo of Pseudochermes fraxini to aid identification Pseudochermes fraxini adults females
Photo of Pseudochermes fraxini to aid identification Pseudochermes fraxini adult females
Ash bark scale Pseudochermes fraxini
Adult female covered by cream coloured felt-like ovisac; about 1 mm long. This species occurs throughout Britain on ash, frequently in very high densities and often becomes a pest in urban areas. In Beds it has been found in Dunstable Down, Luton, Luton Hoo, Swiss Cottage and Whipsnade.

ASTEROLECANIIDAE Pit Scales

Photo of Asterodiaspis quercicola to aid identification Asterodiaspis quercicola empty pit gall
Photo of Asterodiaspis quercicola to aid identification Asterodiaspis quercicola adult female
Golden pit scale Asterodiaspis quercicola
Female test circular, slightly convex, greenish-yellow or yellow, translucent, with whitish marginal filaments; up to 1.6 mm in diameter. This species is common throughout Britain on oak and is an occasional pest. In Beds it has been found in Luton, Luton Hoo, Sandy and Swiss Cottage.

DIASPIDIDAE Armoured Scales

Photo of Carulaspis minima to aid identification Carulaspis minima adult female
Minute cypress scale Carulaspis minima
Adult female cover convex, circular to oval, white; exuviae central, yellow; up to 1.3 mm long. This is a Mediterranean species that feeds on Cupressaceae and is locally common in southern England. In Beds it has been found on Leyland cypress in Sandy.

Photo of Chionaspis salicis to aid identification Chionaspis salicis adult females
Willow scale Chionaspis salicis
Adult female cover convex, oyster-shell shaped, white; exuviae marginal, yellowish brown; up to 3 mm long. This species is very common and widespread in Britain. It is broadly polyphagous and often a pest of forest and ornamental trees and of currant bushes. In Beds it has been found in Bedford, Luton, Luton Hoo, Sandy, Swiss Cottage and Whipsnade; on ash, willow, lilac and lime.

Photo of Diaspidiotus zonatus to aid identification Diaspidiotus zonatus zonatus adult female partially hidden beneath epidermis
Zonate armoured scale Diaspidiotus zonatus
Adult female cover circular to broadly oval, strongly convex, grey, brown or grayish-black; exuviae sub-central, orange; up to 2.8 mm long. This species occurs widely in Britain on oak but is rarely recorded, possibly because it is highly cryptic. This species is often completely hidden beneath the upper epidermal layers of its host. In Beds it has been found in Luton.

Photo of Lepidosaphes ulmi to aid identification Lepidosaphes ulmi adult females
Mussel scale Lepidosaphes ulmi
Adult female cover elongate mussel-shell shaped, convex, brown, dark grey or black; exuviae terminal, orange to brown; up to 3.5 mm long. This species is very common throughout Britain, particularly on Rosaceae and is a serious pest of orchards, forest and ornamental trees. In Beds it has been found in Dunstable Downs, Luton, Luton Hoo and Sandy; on apple, cherry, hawthorn and whitebeam.

INTRODUCED SPECIES ESTABLISHED ON INDOOR PLANTINGS

MONOPLEBIDAE Giant scales

Photo of Icerya purchasi to aid identification Icerya purchasi adult hermaphrodites
Cottony cushion scale Icerya purchasi
Adult hermaphrodites have bright orange-red, yellowish or brown bodies that are partially or entirely covered with yellowish or white wax; up to 6 mm long. They produce a large conspicuous fluted egg sac that may be two and a half times longer than the body. This species has recently become naturalized in the London area and is broadly polyphagous, although it may be restricted to indoor-plantings in Beds. It has been found at a nursery in Sandy on lemon plants imported from Portugal, where it was breeding for several months.

PSEUDOCOCCIDAE Mealybugs

Photo of Planococcus citri to aid identification Planococcus citri adult female
Citrus mealybug Planococcus citri
Adult female oval, grayish, often with a mid-dorsal longitudinal darker stripe, lightly covered in a layer of mealy wax, with 18 pairs of short marginal wax filaments; body length up to 2.5 mm long and 1.5 mm wide. This is a cosmopolitan polyphagous pest that is very common on indoor plantings throughout Britain. In Beds it has been found in Luton on a money plant.

Photo of Pseudococcus viburni to aid identification Pseudococcus viburni adult female
Glasshouse mealybug Pseudococcus viburni
Adult female oval, pinkish or greyish, lightly covered in a layer of mealy wax, with 17 pairs of marginal wax filaments, the caudal pair may be up to half as long as the body; body length up to 2.5 mm long and 1.5 mm wide. It is broadly polyphagous and is a very common pest in Britain of ornamentals grown indoors and outdoors in sheltered situations. In Beds it has been found in Caddington on Carpobroctus, Graptopetalum bellum and a money plant.

COCCIDAE Soft scales

Photo of Coccus hesperidum to aid identification Coccus hesperidum adult female
Brown soft scale Coccus hesperidum
Adult females are oval, flattish, translucent pale-yellow to yellow-brown, often mottled with brown spots; body length up to 5 mm and width 2.5 mm. This species is broadly polyphagous and a common, often serious pest of ornamental and crop plants in Britain. Although it is most commonly recorded on indoor plantings it also frequently occurs outdoors, particularly on bay laurel and ivy. In Beds it has been found in Caddington, Luton and Sandy; on bay laurel, ivy, lemon and umbrella plant.

Photo of Saissetia coffeae to aid identification Saissetia coffeae female and first instars
Hemispherical scale Saissetia coffeae
Post-reproductive females oval, hemispherical, smooth, glossy, yellowish-brown to dark reddish brown; body length up to 4.5 mm and width 4.5 mm. The nymphs and young adults have a distinct characteristic 'H' shaped ridge on the dorsum. It is very common on indoor plantings throughout Britain and is a broadly polyphagous pest of ornamental plants. In Beds it has been found in Caddington on spider plant.

DIASPIDIDAE Armoured Scales

Photo of Pinnaspis buxi to aid identification Pinnaspis buxi adult females
Screwpine scale Pinnaspis buxi
Adult female cover elongate pear-shaped, flattish, brown; exuviae terminal, orange to brown; up to 1.5 mm long. It is established at several botanical collections in Britain. It is broadly polyphagous but most commonly recorded on Palmae. In Beds it has been found at a plant nursery in Sandy on Cordyline imported from Costa Rica.

Further Reading:

"The scale insects and whiteflies (Hemiptera: Coccoidea, Aleyrodidae) of Bedfordshire" by C Malumphy (The plates) was published in The British Journal of Entomology and Natural History 23, 2010. Reproduced here by kind permission of The British Entomological and Natural History Society.

Chris Malumphy
All images © Fera 2009