Six months ago a number of the volunteer plants climbing our chain link fence were suddenly covered by bright yellow, corpulent aphids with black legs, antennae, cauda (tail-like appendage), and cornicles (tubes that extend from the abdomen).
When these aphids encounter suitable host plants, the population explodes. All of the aphids are females. Each reproduces by parthenogenesis (virgin birth), producing many live young (nymphs). If 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 warns predators of the toxic cardenolides (cardiac glycosides) produced by the host plants, that are then incorporated into aphids’ tissues. Predators that feed on aphids avoid these bad tasting insects.
The mortality rate in lacewings that consume these aphids is quite high, while ladybug larvae that feed on these aphids often develop deformed wings prior to their final molt. Spiders that feed on these aphid produce abnormal webs.