Unpalatability is correlated with the level of cardenolides obtained via the larval diet, but other compounds like alkaloids also play a part in promoting distastefulness.

[15] Females lay small white eggs one at a time on larval host plants, usually members of the milkweed subfamily Asclepiadoideae.

[3] The eggs are usually pale green, ovate to conical in shape, with[3] a flattened base and slightly truncated top, and is longitudinally ribbed with raised cross-lines between the ridges.

It has been observed with the following color variants of its transverse stripes: blue, green, yellow, white, and blackish brown.

It is easily distinguishable from its relative the monarch by its darker brown ground colour, and lack of stripes decorating the wings.

[4] Its wing coloration varies from bright, reddish brown to rich chocolate-brown, with black marginal bands that are dotted with white or yellow.

[4] The queen has less-prominent veins on its wings and lacks the darker, apical shading found in the monarch.

[16] The female uses its short forelegs to scratch the surface of a leaf to determine which ones are suitable hosts for its eggs.

[7] The abdominal hair-pencils, when in contact with the androconium scales, are able to disseminate pheromones near the female at integral stages of courtship.

[7][8] The queen belongs to a family (Danaidae) that is common to both New and Old Worlds, specifically found throughout the tropics and into the temperate regions of the Americas, Asia, and Africa.

It displays a more xeric preference in Hispaniola and will fly to the edge of, but seldom penetrate, hammocks and forests.

In the West Indies, blunt-leaved milkweed (Asclepias amplexicaulis) and honey vine (Cynanchum laeve) are favored.

[7][18] Other reported host genera include Apocynum, Cynanchum (former Sarcostemma species), Gonolobus, and Stapelia.

[4] In addition to the above food sources, males are attracted to Heliotropium, Eupatorium, Senecio, and Crotalaria, plants known to contain the alkaloid lycopsamine.

Most of the toxic cardenolides that make queens so unpalatable to its predators are sequestered from larval host plants.

[10] However, the unexpected failure of birds to reject successive queens in an experimental setting[10] called into question the legitimacy of this relationship.

In fact, experimental evidence suggested that Florida viceroys could be significantly more unpalatable than representative queens.

[22] Furthermore, evidence from this study led to the hypothesis that the queen actually enjoys an asymmetric mimicry relationship, gaining an advantage from flying in the company of the relatively more unpalatable viceroy.

It was shown that queens reared on the high-cardenolide A. curassavica sequester and store levels of cardenolides similar to those found in monarchs.

[9] Micro-geographic differences in the environment lead to variation in the dynamics of mimetic relationships even at a local level.

This extensive variation supports the idea that automimicy occurs at the intrapopulation level – palatable queens mimic individuals that have higher cardenolide content.

[23] Queen unpalatability does not directly mirror either food plant or butterfly cardenolide content.

[9] Evidence suggests that the interaction of cardenolides and noncardenolides are utilized for chemical defenses in milkweed butterflies.

Wild queens that fed upon S. clausum as larvae but had access to adult-obtained compounds, such as the pyrrolizidine alkaloids (PAs) used for pheromone production, were observed to be significantly less palatable to avian predators than butterflies without chemical defenses.

Later, the female will fly closer to the ground than normal to find a suitable host for egg deposition.

[18] During courtship, which occurs while both butterflies are in flight, the male everts his hair-pencils and brushes them against the female's antennae.

This liquid secretion moves from these cells, through the cuticle of the hairs, to coat the numerous free, cuticular dust particles that adhere to the hair-pencil surface.

[26] Two of the chemicals that comprise this secretion have been identified – a crystalline pyrrolizidinone (ketone) and a viscous terpenoid alcohol (diol).

Male queen butterflies with physically normal but chemically deficient hair-pencils also suffer from lower mating success.