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- Jan 27, 2010
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- 800 × 770
- Original date:
- Oct 02, 2006
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"The oleander aphid (Aphis nerii Boyer de Fonscolombe) is a distinct bright yellow aphid with black legs, antennae, cauda (tail-like appendage), and cornicles (tubes that extend from the abdomen). It is thought to originate in the Mediterranean and probably spread as oleanders were introduced around the world. The aphid is now found in tropical and temperate zones worldwide.
When the oleander aphid finds its preferred hosts, plants in the Asclepiadaceae and Apocynaceae, the population explodes. All of the aphids are females; they reproduce by parthenogenesis (clones of the mother) and they bear live young (nymphs). If conditions become too crowded on a plant or the plant declines in health, some of the aphids develop wings and will colonize new plants.
The aphids' bright coloring is a warning to predators. The aphids sequester the cardenolides (cardiac glycosides) produced by the milkweeds and dogbanes. When a predator disturbs the aphids, they exude the cardenolides in a waxy compound through the cornicles. Predators usually back away and clean the defensive compound from their mouthparts.
The amount of cardenolides present in milkweeds and dogbanes varies with the species, the age of the plant, and the season. Aphids that feed on plants with low amounts of the glycosides are more likely to fall prey to generalist predators like spiders, ladybug larvae, and aphid lions (lacewing larvae).
Generalist predators that survive eating the oleander aphids suffer the effects of the cardenolides. Fewer aphid lions survive to become lacewings and reproduce. Ladybugs develop deformed wings. And spiders weave strange disrupted webs.
The Bug Guide has posted a great photograph of oleander aphids taken by Lynette Schimming. To view these aphids on a milkweed, click on the link:"
bugguide.net/node/view/10569/bgpage
Wikipedia Article
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 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.
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