Soon after I first saw them, the monarch caterpillars disappeared off the milkweed in my yard. Oleander aphids (Aphis nerii) soon took their place.
These orange-yellow blobs suck milkweed sap, slowly expanding in size. They have sharply contrasting black legs and black cornicles. Cornicles are the short horn-like tubes you see sticking out of the back of each aphid. They are used to secrete an alarm pheremone that warns other aphids of the presence of a predator.
These aphids do have natural predators including wasps and bugs, but I did not see any on my plants.
Only female oleander aphids have been found in the wild. Females give live birth to their young, which may be born containing babies of their own. Since no eggs or fertilization are involved, all oleander aphids on a plant are clones.
When an aphid molts, it leaves behind a white exoskeleton, which you can see in the photo below.
When aphids sense that it is time to move on, either because of crowding or because the plant isn’t doing so well, they produce winged forms. Winged aphids can fly to another plant to start a new colony.
I found a red aphid among all the yellow. This is probably the red sunflower aphid (Uroleucon helianthicola), which has fallen off a nearby sunflower plant.
So what happened to the milkweed caterpillars? They could have been taken by a predator. They could have been washed off the plant or died of natural causes. Or they could have been forced off the plant because the owner wanted to convert it to condos and flip it. No, wait, that’s what happened to me.