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. 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.The queen is one of many insects that derives chemical defenses against its predators from its food plant. Most of the toxic cardenolides that make queens so unpalatable to its predators are sequestered from larval host plants.