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Aphids (Superfamily Aphidoidea) Are Small Sap-sucking Insects

Aphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, (not to be confused with “jumping plant lice” or true whiteflies) are small sap-sucking insects and members of the superfamily Aphidoidea.

Aphids are among the most destructive insect pests on cultivated plants

Aphids (Superfamily Aphidoidea) Are Small Sap-sucking Insects
Nymph aphids surrounding the mother aphid

Aphids are among the most destructive insect pests on cultivated plants in temperate regions.The damage they do to plants has made them enemies of farmers and gardeners the world over, but from a zoological standpoint, they are a very successful group of organisms. Their success is in part due to the asexual reproduction capability of some species.

About 4,400 species of 10 families are known. Historically, many fewer families were recognised, as most species were included in the family Aphididae. Around 250 species are serious pests for agriculture and forestry as well as an annoyance for gardeners. They vary in length from 1 to 10 millimetres (0.04 to 0.39 in).
Natural enemies include predatory ladybirds, hoverfly larvae, parasitic wasps, aphid midge larvae, crab spiders, lacewings and entomopathogenic fungi like Lecanicillium lecanii and the Entomophthorales.

Predators of aphids

Aphids are soft-bodied and have a wide variety of insect predators, which are often infected by bacteria, viruses and fungi. They are affected by the weather, such as precipitation, temperature and the wind.

Insects that attack aphids include predatory Coccinellidae (lady bugs or ladybirds), hoverfly larvae (Diptera: Syrphidae), parasitic wasps, aphid midge larvae, “aphid lions” (the larvae of green lacewings), crab spiders and lacewings (Neuroptera: Chrysopidae).

Fungi that attack aphids include Neozygites fresenii, Entomophthora, Beauveria bassiana, Metarhizium anisopliae and entomopathogenic fungi like Lecanicillium lecanii. Aphids brush against the microscopic spores. These spores stick to the aphid, germinate and penetrate the aphid’s skin. The fungus grows in the aphid hemolymph (i.e., the counterpart of blood for aphids). After about 3 days, the aphid dies and the fungus releases more spores into the air. Infected aphids are covered with a woolly mass that progressively grows thicker until the aphid is obscured. Often the visible fungus is not the type of fungus that killed the aphid, but a secondary fungus.

Aphids can be easily killed by unfavourable weather, such as late spring freezes. Excessive heat kills the symbiotic bacteria that some aphids depend on, which makes the aphids infertile. Rain prevents winged aphids from dispersing, and knocks aphids off plants and thus kills them from the impact or by starvation. However, rain cannot be relied on for aphid control.

Credits / references:
From Wikipedia, the free encyclopaedia
Photo by: Shipher Wu (photograph) and Gee-way Lin (aphid provision), National Taiwan University

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