Dogbane leaf beetles mate, feed and grow on the Dogbane plant. Adults feed on the leaves of the plant. They also find mates on the plant. Females lay a couple of fertilized eggs in a pile of their own feces and attach the sticky clump to the underside of a leaf. Once hatched, the Dogbane Leaf Beetle larvae chew their way out of the feces pile and then drop to the base of the plant, burrowing down to feed on the roots. The result of all of this is death to the Dogbane plant.
Dogbane plants are also known as Indian Hemp, or American Hemp. This plant's fibrous stem was historically used to make thin cords and ropes, and it still is. Archaeological digs have even found remnants of such cords implying it was used by Native Americans. The plant is also known to have some medicinal uses, though not much since the 1950's. The plant actually produces a toxin, which in small doses or special preparations, was somewhat useful, but on the whole, it is still poisonous to humans and animals. In fact, dogs (and sheep and other livestock) were kept away from this toxic plant because ingesting its sweet, sticky sap caused death.
The Dogbane Leaf Beetle could be considered a pest of a useful plant, or a control for a deadly one. None of this, however, detracts from the Dogbane Leaf Beetle's keen ability to carve out a niche for itself in the 'dog-eat-dog' insect world.