Troides helena common in many of the localities in which it occurs, was classified as vulnerable in 1985. Helen in Greek mythology Helen was the daughter of Zeus. Cerberus or Kerberos, in Greek and Roman mythology, is a multi-headed hound which guards the gates of the Underworld. This species is protected under Wild Animals Protection Ordinance Cap 170 in Hong Kong. The common birdwing is protected in Indonesia and may also require protection in peninsular Malaya also. It is listed in Appendix II of Convention on the International Trade in Endangered Species of Wild Flora and Fauna (CITES) as are all other
The Dog It Was That Died be seen as the mad dog of the poem. Stoppard may have borrowed the idea to use this quotation from British novelist W. Somerset Maugham's 1925 "The Painted Veil", in which the protagonist's husband, bitter at her infidelity, brought her to cholera-stricken China in hopes that she would take ill and die. When he catches cholera instead, he dies with the quotation "The dog it was that died" on his lips. The words also occur in a speech by Wormold, the lead character in Graham Greene's 1958 novel "Our Man in Havana" – also an entertaining tale of Cold War