Order Hemiptera - Suborder Homoptera

• Aphid or Greenfly
• Whitefly
• Mealybug
• Scale Insect
• Froghopper or Spittlebug
• Leafhopper
• Treehopper
• Cicada
• Lantern Fly
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Description. Up to 3 mm long. Body colour rather variable, from yellowish through green to dark brown. Legs and antennae usually more or less black. Cornicles always black. Like most aphids, it has winged and wingless forms.

Biology. Found on cereals and grasses, usually feeding on the underside of leaves and on the flower heads. May cause considerable crop losses when feeding on the ripening ears of wheat, oats and other cereals. It is also a vector of some cereal and grass virus diseases. Reproduction is generally asexual, with several generations during the year. The asexual females give birth to live young. Winged asexual forms are produced at certain times of year, particularly in summer and autumn, and these fly off to colonise new plants. Sexual forms (males and females) are sometimes produced in autumn and after mating the sexual females lay overwintering eggs, which hatch in the following spring. This is a fairly typical aphid, similar to many of the species commonly found on vegetable crops and ornamental plants, and known as greenfly, blackfly or plant lice. The life cycle of some species is even more complex than that of the Grain Aphid, involving alternation and migration between different summer and winter host plants. For example, the Black Bean Aphid (Aphis fabae) lives on beans, spinach, docks and other herbaceous plants during the summer, but migrates to spindle (Euonymous sp.) and a few other trees in autumn, to spend the winter. There is a return migration to the summer host plants in spring.

Distribution. The Grain Aphid occurs throughout Europe and the British Isles. Also found in North America and Japan.

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Winged, asexual female

Wingless, asexual female
and a young nymph

Description. Small insects, 1-2 mm long, with the body and wings dusted with a white powdery wax.

Biology. A damaging pest found on the undersides of leaves and infesting many glasshouse and indoor plants, especially tomatoes and cucumbers. Sometimes occurs on outdoor plants and weeds in summer. Breeding continues throughout the year in heated glasshouses and is mainly asexual. Adults may live for a month or more and each female lays up to 200 eggs on the undersides of leaves. The young nymphs crawl about on plants for a few hours after hatching, but then settle to feed. Their legs and antennae degenerate and they become immobile scales which feed for about 2 weeks before entering a non-feeding stage from which the adults emerge. Development from egg to adult takes about 3-4 weeks in warm conditions. Biological control is widely used in commercial glasshouses, by introduction of a small parasitic wasp, Encarsia formosa, which attacks and kills the whitefly scales. Other biological controls becoming available to gardeners include a small black ladybird, Delphastus sp., and a small predatory bug, Macrolophus sp.

Distribution. Native of Central America, but has been imported and spread by trading and now occurs in North America, Europe, Britain and other temperate regions, where it can survive harsh winters in heated glasshouses.

Photo: V.J. Stanek ©

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Adults

Scale-like nymph
(non-feeding stage)

Description. Wingless females and young stages (illustrated) are up to 6 mm long and covered with a white or yellowish wax secretion. The males are 1-2 mm long, lemon-yellow in colour, with a single pair of white wings.

Biology. This and several other similar species are common pests of glasshouse and conservatory plants. They live on leaves, stems, buds, flowers and fruits. Persistent infestations weaken the plant and cause fouling of the plant surfaces with sticky honeydew on which sooty moulds tend to grow. Females lay batches of 100-150 eggs protected by a covering of woolly wax. In warm conditions, eggs may hatch in a few days and the young mealybugs then crawl over the plant for a few hours before settling to feed. They often remain immobile for long periods whilst feeding, but can move to new feeding sites when necessary. Development from egg to adult may be as short as three weeks. The winged males emerge from delicate white cocoons, but are short-lived, surviving just a few days for the purpose of mating.

Distribution. Cosmopolitan, but confined to glasshouses in colder climates.

Photo: V.J. Stanek ©

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Nymphs and adult females

Description. Females sessile, living under brownish, mussel-shaped scales, up to 3 mm long, and form dense colonies on woody stems. Males tiny, about 1 mm long, but quite mobile and active, with a single pair of wings; body and wings mainly whitish in colour, with pale yellow antennae, legs and thorax.

Biology. These insects attack many deciduous trees and shrubs, including apples and other fruit and ornamental trees. Infestations are most severe on older trees and may impair plant growth and vigour. Eggs are laid under the scales in late summer. These overwinter and hatch in the following spring. After hatching, the first stage nymphs crawl about over the plant and are responsible for the dispersal of the insects. Legs are lost after this stage and older nymphs then remain sessile, attached to the plant only by their mouthparts. At this stage they start to form their protective scales. In Britain, whereas the female scales have a very wide host range, the males are often found more commonly on certain food-plants, such as broom (Sarothamnus, = Cytisus), bilberries (Vaccinium) and heathers (Erica). The adult male insects emerge in summer, but live only a few days for the purpose of mating. Usually one generation a year outdoors in temperate regions.

Distribution. British Isles and many parts of Europe. The insect has also become a pest in North America, where it is known as the Oystershell Scale.

Photo credit ©

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Female scales

Male

Description. Adults about 10 mm long, black with bright red markings on the forewings (there are several very common froghoppers of similar form, but dull brown in colour and much less conspicuous). Young stages are pale yellowish-green.

Biology. The soft-bodied young stages (nymphs) develop in a frothy, protective envelope of their own making, in most cases attached around plant stems and leaf stalks and commonly known as 'cuckoo-spit'. Hence, such locally common names as spittlebugs and cuckoo-spit insects. However, the nymphs of Cercopis species live underground, feeding communally on plant roots and surrounded by solidified froth. The adults are known as froghoppers, from their leaping ability and vaguely frog-like appearance, particularly when poised to jump.

Distribution. Central Europe, although very similar red and black species occur elsewhere in Europe and in the British Isles (e.g., the common and widespread, Cercopis vulnerata).

Photo: V.J. Stanek ©

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Adult

Description. About 6 mm long, head and legs pale yellow-green, thorax and wings blue-green with bright red spots and banding. Nymphs bright yellow.

Biology. Feeds on the buds, young leaves and shoots of rhododendrons, azaleas, forsythia and other ornamental shrubs. There is no obvious feeding damage to plants, but attacks by this pest seem to encourage fungal infections, especially the spread of bud blast disease in rhododendrons and azaleas (caused by the fungal pathogen, Pycnostysanus azaleae). Adults appear in late summer. They sit on buds and leaves, jumping and flying briefly when disturbed but soon re-settling. Females lay their eggs in shallow slits cut into the outer scales of flower buds. The eggs overwinter and hatch the following spring. The nymphs feed on the undersides of leaves and mature by the end of summer.

Distribution. British Isles, northern Europe, eastern parts of North America.

Photo: D.C. Stager ©

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Adult

Description. About 14 mm long, coloured green, with reddish borders around the edges of its body and on the thorn-like process of its thorax. The thorax extends backwards to form a sort of hood over the wings and abdomen.

Biology. Treehoppers are mainly tropical insects and usually live on trees. They show many examples of protective resemblance, as in the species illustrated, which in shape mimics the thorns of its food-plant. Like other hoppers, they have the ability to leap away when disturbed, sometimes to a considerable distance relative to their size.

Distribution. Central and South America.

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Adult

Description. Adult 35-40 mm long, mottled brown with large clear wings. This species has conspicuous black spots at the junctions of some of the wing veins.

Biology. Cicadas are mainly tropical and sub-tropical species, well known for their shrill, noisy 'singing'. The adults are fairly short-lived, lasting only a few weeks, but the nymphs, which live underground feeding on plant roots, may take several years to complete their development. An extreme example is the so called Periodical Cicada of North America, Magicicada septendecim, where nymphal development takes 17 years.

Distribution. The species illustrated comes from Europe.

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Adult

Description. Adult about 50-60 mm long, with a bladder-like outgrowth at the front of the head. Mainly brown in colour, but with a striking 'eye-spot' pattern on each hindwing.

Biology. Despite its name, it is not a fly and does not produce light. Many species have the head enlarged and protruding forward between the eyes. In some cases, this outgrowth is almost as long as the rest of the body and decorated with spines, bumps and curious patterning. The example illustrated is a large South American species, in which the outgrowth resembles the head of an alligator or crocodile. The purpose of such an elaborate feature is unknown.

Distribution. South America.

Photo: H. Schultz ©

Head and thorax of the adult