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plant louse,

tiny, usually green, soft-bodied, pear-shaped insect injurious to vegetation. It is also called greenfly and blight. Aphids are mostly under 1-4 in. (6 mm) long. Some are wingless; others have two pairs of transparent or colored wings, the front pair longer than the hind pair. In typical aphids (family Aphididae), two tubes called cornicles project from the rear of the abdomen and exude protective substances. Aphids feed by inserting their beaks into stems, leaves, or roots, and sucking the plant juices. Usually they gather in large colonies.

The life cycle of aphids is complex and varies in different species. In a typical life cycle, several generations of wingless females, which reproduce asexually (see parthenogenesisparthenogenesis
[Gr.,=virgin birth], in biology, a form of reproduction in which the ovum develops into a new individual without fertilization. Natural parthenogenesis has been observed in many lower animals (it is characteristic of the rotifers), especially insects, e.g.
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) and bear live offspring, are followed by a generation of winged females, which bears a sexually reproducing, egg-laying generation of males and females. Mating usually occurs in fall, and the eggs are laid in crevices of the twigs of the host plant; the first generation of wingless females hatches in spring. Different host plants and different parts of the plant may be used at different stages of the life cycle.

Some aphids (e.g., the woolly apple aphid) secrete long strands of waxy material from wax glands, forming a conspicuous woolly coating for their colonies. Gall-making aphids live in gallsgall,
abnormal growth, or hypertrophy, of plant tissue produced by chemical or mechanical (e.g., the rubbing together of two branches) irritants or hormones. Chemical irritants are released by parasitic fungi, bacteria, nematode worms, gall insects, and mites.
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, or swellings of plant tissue, formed by the plant as a reaction to substances secreted by the insects; galls of different aphid species are easily identified (e.g., the cockscomb gall of elm leaves). One group of aphids lives only on conifers (e.g., the eastern spruce gall aphid).

Ant Cows

Many kinds of aphid secrete a sweet substance called honeydew, prized as food by ants, flies, and bees. This substance consists of partially digested, highly concentrated plant sap and other wastes, and is excreted from the anus, often in copious amounts. Certain aphid species have a symbiotic relationship with various species of ants that resembles the relationship of domestic cattle to humans; hence the name "ant cows" for aphids. The ants tend the aphids, transporting them to their food plants at the appropriate stages of the aphids' life cycle and sheltering the aphid eggs in their nests during the winter. The aphids, in turn, provide honeydew for the ants.

Damage to Plants

The damage done by aphids is due to a number of causes, including loss of sap, clogging of leaf surfaces with honeydew, and growth of molds and fungi on the honeydew. Leaf curl, a common symptom of aphid infestation, occurs when a colony attacks the underside of a leaf, causing its desiccation. The downward curl provides protection for the colony, but the leaf becomes useless to the plant. Some species also transmit viral diseases of plants. Among the aphids causing serious damage to food crops are the grain, cabbage, cornroot, apple, woolly apple, and hickory aphids and the alder and beech tree blights. The phylloxeraphylloxera
, small, sap-eating, greenish insect of the genus Phylloxera, closely related to the aphid. Phylloxeras feed on leaves and roots, and many species produce galls on deciduous trees.
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, notorious for its damage to vineyards, is closely related to the aphids.

Many larger insects that feed on aphids, such as ladybird beetles and lacewings, are used as biological controls of aphid infestations. Fungal infection and damp weather also help limit the number of aphids.


Aphids are classified in several families of the phylum ArthropodaArthropoda
[Gr.,=jointed feet], largest and most diverse animal phylum. The arthropods include crustaceans, insects, centipedes, millipedes, spiders, scorpions, and the extinct trilobites.
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, class Insecta, order Homoptera.


(invertebrate zoology)
The common name applied to the soft-bodied insects of the family Aphididae; they are phytophagous plant pests and vectors for plant viruses and fungal parasites.


any of the small homopterous insects of the family Aphididae, which feed by sucking the juices from plants
References in periodicals archive ?
Although ladybugs and their larvae have voracious appetites for aphids and other small insects, don't expect the adults to provide control once you release them from a mailing container into your garden.
The aphids that were not exposed to spore-crystal suspensions remained in constant movement, continued feeding, and did not show any change in color during the first 48 h; after 60 h, these aphids became sessile, and their green color changed to a pale greenish brown (Fig.
Even though that the five used oils showed significant mortality to the aphid at a concentration of 1000 ppm compared with the negative control, DMSO solution, but none of them was as toxic as Actara insecticide did after 24 and 48 hr of treatment (Table 1).
Scientist, National Bureau of Agricultural Important Insects (ICAR), Bengaluru, India for identification of aphid specimens.
As a virion, the virus moves from plants to aphids, through aphids, and back into plants, and the topology of the virion guides the transmission process," Gray says.
The study was conducted in the following two goals: (i) to evaluate the effect of the tested products in reducing the aphid population on infested plants and (ii) to verify the ability of the tested products in preventing the colonization of treated cotton plants exposed to aphid colonization.
Lady beetles reduced aphid densities on goldenrod stems from heavy to light after 24 hr in both years of testing among all species, except that H.
and colleague Michael Dossett of Agriculture and Agri-Food Canada are the first to find and report black raspberry resistance to the large raspberry aphid.
Regarding aphid population the individual effects of varieties, treatments and dates and their interaction effects were highly significant.
I don't know where the ants went (I don't care) and my cherry tree lived a long healthy ant and aphid free life until I George Washingtoned it.
In Brazil, the giant conifer aphid, Cinara atlantica (Wilson, 1919) has damaged commercial plantations of Pinus spp.
Transmitted by green peach aphid (GPA), the combination of virus and aphid feeding has caused considerable damage and crop losses in parts of South Australia and Victoria, and infection has also been detected in southern New South Wales.