How does the oleander aphid protect herself?

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By Chelsie Vandaveer

April 13, 2005

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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.

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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:

http://bugguide.net/node/view/10569/bgpage

This is wonderful 'bug' site. Follow links on the page to learn about all sorts of insects.

(Compiled from: "Effects of variation among plant species on the interaction between a herbivore and its parasitoid", S.E. Helms, S.J. Connelly, and M.D. Hunter, Ecological Entomology, Vol 29, Royal Entomological Society, 2004; "Oleander Aphid", Drees and Jackman, Field Guide to Texas Insects, 1999, published on the internet by Texas Cooperative Extension, Texas A&M University; and "Aphids", Institute of Food and Agricultural Sciences, University of Florida, 2002.)

killerPlants Tendrils: ~~1~~2~~3~~4~~5~~

Suggested Reading:

Oleander (Nerium oleander Linnaeus) Plant of the Week - September 22, 2003
What is the polka-dot wasp moth? Renfield's Garden - October 8, 2003
Desert Rose (Adenium obesum) Plant of the Week - August 26, 2002
What is a hairy potato? Renfield's Garden - October 10, 2001
What are witches' brooms? Weird Plants - October 31, 2002

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