Milkweed and insects

Title Info
Common name Milkweed
Scientific name Asclepias curassavica
Taxonomic group Asclepiadaceae
Source Dan L. Perlman
Ecological interactions Herbivory; Competition
Organisms Animals
Animals Insects
Date 1988
Location Monteverde,Puntarenas,Costa Rica,North America

Milkweed and insects: mutualists, herbivores, or competitors, Monteverde, Costa Rica. This brightly colored milkweed is being visited by representatives of four different insect orders: an ant, a beetle, a true bug, and a group of aphids (the yellow dots in the back on the right). Determining the relationships among them may not be simple. The yellow aphids in the background on the right are sucking a tremendous amount of sap from the plant and could easily be seen as herbivores, except that some species of aphids attract ants that tend them and also protect the host plant against other herbivores (an overall benefit for the plant). Although ants have the potential to be good defenders of the plant, a single small ant may not do the job. The true bug, the large insect on the left, appears to be taking nectar, which sounds like part of a mutualistic relationship with the milkweed, but if the insect doesn't pollinate the plant, it may be cheating on the system. It is hard to say what the beetle is doing. It is also difficult to say whether the insects, all of which are using a single resource, the milkweed, are competing for that resource or not. The insects all appear to be using the resource in different ways, so there may actually be no competition here at all.