Aphids

More than 1,300 species in North America north of Mexico

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several yellow aphids on plant
Aphids are soft-bodied, plump, pear-shaped, and tiny. They suck plant juices. They have two tubelike projections on the hind end of the body, called cornicles, which aid in defense. Aphids are commonly green, yellow, or brown, but the color varies among the many, many species.
Donna Brunet
Family

Aphididae (aphids) in the order Hemiptera (true bugs)

Description

Because of their complex life cycle, a single species of aphid can have different body forms, some four-winged, but mostly wingless. Overall, they are soft-bodied, plump, pear-shaped, and tiny. All aphids have two tubelike projections on the hind end of the body, called cornicles or siphunculi, which apparently emit scents that warn other aphids of danger or can emit a defensive goo to deter predators. Aphids are commonly green, yellow, or brown, but the color is quite variable among the many, many species. Most aphids are slow-moving and sedentary.

Size

Length: to about 1/4 inch (varies with species).

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Green lacewing larva eating aphids
Green Lacewing Larva (Aphid Lion) With Aphids
Green lacewing larvae are long, flattened, segmented, and lizard-like, with six legs and sickle-shaped mouthparts. "Aphid lions" are insatiable predators of aphids, grasping them with grooved, caliper-shaped jaws, lifting them in the air, and letting the aphid's fluids drain into the aphid lion's mouth.

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Several black aphids being tended by golden-brown ants
Aphids With Ants
Ants tend aphids, collecting their sugary secretions. Note that a few of these aphids are giving birth to live young, and the aphids at left are juveniles.

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Several yellow aphids on the underside of a milkweed leaf
Aphids on Milkweed Leaf
Aphids jab the pointed tubes of their mouths into a leaf, flower, or stem, then suck sap from the plant. Aphids are sometimes called “plant lice.”

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Lady beetle larva with aphids
Lady Beetle Larva With Aphids
Lady beetle larvae are long, segmented, soft-bodied, and lizard-like, with six legs, and are often gray, tan, black, and brown, with small bristles. They devour aphids, which suck the sap from plants.
Habitat and conservation

Aphids are usually found on their host plants. Some species require certain types of plants and can be indentified, in large part, by naming the plant they are on. Other species aren’t so particular. Many aphids are serious agricultural and garden pests, as their feeding deprives the plant of nutrients and the punctures they make injure the plant’s veins. Aphids sometimes transmit diseases to plants, the way mosquitoes and ticks can transmit diseases to people.

Foods

Aphids, like all members of the “true bug” family, have strawlike mouthparts specialized for piercing and sucking. They jab the pointed tubes of their mouths into a leaf, flower, or stem, then suck the sap from the plant. Because this is essentially what lice do to animals, aphids are sometimes called “plant lice.” Because plant juices are high in sugar, excess sugars are excreted by aphids, sometimes abundantly. This fluid, called honeydew, is collected as food by ants and other insects.

image of Aphids Distribution Map
Distribution in Missouri

Statewide.

Status

Common.

Life cycle

Aphids have a complex life cycle. After overwintering as eggs, the aphids that hatch in spring are all females and reproduce asexually (without mating). Their offspring, which are born live (not hatching from eggs), are genetically identical to their mothers. At some point, the females give birth to aphids that develop wings, which can disperse from the original colony. Late in the season, male and female forms are born. These mate, and eggs are laid to overwinter for the next season.

Human connections

Aphids can cause serious damage to crops and garden plants, wilting them and sometimes transmitting diseases. The honeydew they excrete can cause sooty mold on plants and can leave spots on cars and other objects. Fortunately, many insects prey on aphids and keep them in check without help from us.

Ecosystem connections

Lacewings, lady beetles, and hordes of other insects prey on sweet, juicy aphids. Other insects, especially certain ants, collect the honeydew, an important food source for them. Some ants stroke aphids, “milking” them for honeydew, and repay their aphid “herds” by defending them from harm.