The Milkweed Aphid or Oleander Aphid (Aphis nerii) is commonly found on many milkweed species. These tiny insects feed upon the sap of plants in the dogbane family (Apocynaceae) which includes the milkweeds (formerly in their own family of Asclepiadaceae). These lemon-yellow colored aphids scream "don't eat me" with their bright coloration ... which is probably a deterrent characteristic that has evolved over time because of the poisonous alkaloids that the insect ingests from the milkweed sap and deposits within their own bodies.
Interestingly, larva of predators such as lacewings or lady beetles that do feed upon these yellow-colored aphids may have developmental problems as they morph into adults, such as wing deformities or even failure to morph (death).
This aphid species is what is referred to as "parthenogenetic", meaning that they are able to reproduce without males. Both winged and wingless females are produced by live-birth and are called "nymphs" that are exact genetic copies of the mother ... thus producing clones. Large colonies, as the photo shows, often develop over the summer. As with most aphids, the milkweed aphid secretes a viscous sugary substance called "honeydew" that attracts ants and also leaves a black, sticky, sooty-colored mold.
