Monarchs rely on milkweed as the sole host plant for their caterpillars, and without it, their populations struggle to thrive ...

Scientists have long known that milkweed cardenolides, which in most animals disable a vital sodium-potassium pump enzyme if they are absorbed into the blood, serve to make caterpillars and ...

A Pennsylvania butterfly farmer says listing the monarch as a threatened species could do more harm than good.

The population wintering in central Mexico's forests occupied 4.42 acres, up from 2.22 acres during the previous winter.

It's hard to believe that milkweed has nearly disappeared from Vermont's landscape in just a few short years. In the Green Mountain State, corn crops are everywhere and along the edges of those fields ...

Milkweed is the only plant monarch caterpillars will eat, and the adult monarchs will lay their eggs on, according to the National Wildlife Federation. And with a declining habitat, it is ...