The queen butterfly (Danaus gilippus) is a North and South American butterfly in the family Nymphalidae with a wingspan of 80–85 mm (3+1⁄8–3+3⁄8 in). It is orange or brown with black wing borders and small white forewing spots on its dorsal wing surface, and reddish ventral wing surface fairly similar to the dorsal surface. The ventral hindwings have black veins and small white spots in a black border. The male has a black androconial scent patch on its dorsal hindwings. It can be found in meadows, fields, marshes, deserts, and at the edges of forests. This species is possibly a close relative to the similarly colored soldier butterfly (or tropical queen, D. eresimus), in any case, it is not close to the plain tiger (D. chrysippus, African queen) as was long believed. There are seven subspecies. Females lay one egg at a time on larval host plants. Larvae use these plants as a food source, whereas adult butterflies feed mainly on nectar from flowers. Unpalatability to avian predators is a feature of the butterfly; however, its level is highly variable. 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. Males patrol to search for females, who may mate up to 15 times a day. Male organs called hair-pencils play an important role in courtship, with males with lower hair-pencil counts being selected against. These hair-pencils may be involved in releasing pheromones during courtship that could attract female mates.
Taxonomy The queen is a member of the genus Danaus, which includes D. plexippus (monarch) and D. eresimus (soldier). It is of the family Nymphalidae of the order Lepidoptera. There are as many as eleven subspecies recognized. It is a native of the Nearctic and Neotropical realms. The conservation status of this species is secure, with no reported management needs.
Life cycle and morphology Females lay small white eggs one at a time on larval host plants, usually members of the milkweed subfamily Asclepiadoideae. The egg hatches into a black caterpillar with transverse white stripes and yellow spots, and three pairs of long, black filaments. The caterpillar feeds on the host plant and sequesters chemicals that make it distasteful to some predators. It then goes through five instars, after which the larva finds a suitable spot to pupate. The adult emerges 7 to 10 days afterwards. The queen butterfly has multiple generations per year.
Egg The queen butterfly oviposits one egg at a time. Each individual egg can be found on leaves, stems, and flower buds of the host. The eggs are usually pale green, ovate to conical in shape, with a flattened base and slightly truncated top, and is longitudinally ribbed with raised cross-lines between the ridges. Compared to that of the monarch butterfly, the egg of the queen butterfly is taller relative to its width.
Caterpillar The mature queen caterpillar is darker and not as brightly colored as the monarch caterpillar. It is nearly identical to the caterpillar of Danaus chrysippus. In the larval stage, the queen is bluish-white dorsally, with a reddish-brown underside. It has three pairs of black, fleshy tentacles—one is on the head, one is on the second thoracic segment and one is on the eighth abdominal segment. When mature, the caterpillar is brown with purplish prolegs. It has been observed with the following color variants of its transverse stripes: blue, green, yellow, white, and blackish brown. The head is black with white rings. The caterpillar lacks spines, and there is no hair on its body.
Pupa The pupa is relatively short and thick, tapering rapidly at the end of the abdomen. It is pale green, rarely pale pink, and is frequently ornamented with golden spots. A black transverse band edged with gold is on the abdomen. Below this black abdominal band lies another one in blue. The pupa has very few projections; most notably, it is suspended by a long cremaster from a button of silk. As such, the pupa resembles a pendant. In general, the pupa of the queen is smaller and more slender than that of the monarch.
Butterfly The queen butterfly is related to two species to which it bears a striking resemblance: the monarch (Danaus plexippus) and the soldier (Danaus eresimus). The queen is a moderately large butterfly, with an average wingspan of 3.1 inches (7.9 cm) to 3.3 inches (8.4 cm). It is easily distinguishable from its relative the monarch by its darker brown ground colour, and lack of stripes decorating the wings. The queen bears a closer resemblance to the soldier (Danaus eresimus). It possesses a very tough and flexible chitinous exoskeleton, unlike most other butterflies. Its wing coloration varies from bright, reddish brown to rich chocolate-brown, with black marginal bands that are dotted with white or yellow. The underside of the wing resembles the upper wing, but is paler. The queen has less-prominent veins on its wings and lacks the darker, apical shading found in the monarch. Both sexes are morphologically similar. The male's and the female's forewing lengths range from 3.7 centimetres (1.5 in) to 4.6 centimetres (1.8 in), with a mean length of 4.2 centimetres (1.7 in). The antennae lack scales. Although all danaids have two pairs of walking legs, the forelegs, the first pair located on the prothoracic segment of the abdomen, are reduced and not used for locomotion. The forelegs are relatively smaller in the male than in the female. The female uses its short forelegs to scratch the surface of a leaf to determine which ones are suitable hosts for its eggs. In both sexes, the reduced forelegs lack claws. The male queen has an androconium, a specialized, scale-covered scent-pouch, on each of its dorsal hindwings. The positions and structures of androconia are used to identify different genera. The male also has an extensible hair-pencil on each side of its abdomen, which exudes sex pheromones. The abdominal hair-pencils, when in contact with the androconium scales, are able to disseminate pheromones near the female at integral stages of courtship.
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