This queen ain't no monarch but it's still related to butterfly royalty. The queen butterfly can be mistaken for the better known cousin monarch butterfly, and the resemblance is no accident.

Both the queen and the monarch are members of the same genus — Danaus — D. gilippus, in the case of the queen. Both use milkweed as a host plant, as does a third member of the clan, the soldier, which looks so much like its cousin, it's sometimes called the tropical queen.

Females of the Danaus clan lay their eggs on the leaves, stems and flower buds of various milkweed species. The caterpillars munch on the plant and take in toxins — cardiac glycosides called cardenolides. These chemicals give Danaus butterflies, including the queen, their trademark dark-orange color. It also makes both the caterpillars and adults poisonous to any vertebrate predator, birds in particular, that might eat one.

Adults signal the presence of the toxin via their orange coloration. A bird that tries to dine on the queen, monarch or soldier (or a third, distant cousin called the viceroy) will associate the color of his meal with the resulting severe stomach ache and more than likely stay away from eating anything orange.

The differences between the species are somewhat subtle but theasiest way to tell the species apart is this: soldiers and monarchs (and viceroys, which closely resemble monarchs) have dark, heavy veins on the upper side of their wings; the veins on queens are fine.