Knowing Danaids

Crows and Tigers
Danaids can be divided into two kinds — Crows and Tigers. Crows usually have dark brown wings; there is purple-blue with metallic lustre on the surface of the wings under sunlight. The wings of Tigers have stripes of strong contrasting colours.

Crow: Blue-spotted Crow (Euploea midamus)

Tiger: Common Tiger (Danaus genutia)

Highly poisonous
The caterpillars of Danaids eat poisonous plants. For instance, Plain Tiger (Danaus chrysippus) caterpillars eat toxic Blood-flower (Asclepias curassavica); Blue-spotted Crow (Euploea midamus) eat Goat Horns (Strophanthus divaricatus), which is one of the four most poisonous plants in Hong Kong. After consuming these poisonous plants, the toxins will remain in the bodies. Also, the bodies of danaid caterpillar are brightly coloured, warning hunters of how toxic they are. After they metamorphose into adults, the toxins and warning colours remain.

Blood-flower

Goat Horns

Mimicry of other butterflies
The warning colours of adult Danaids are divided into two categories: strong contrasting colours and patches of metallic colours. These warnings of toxicity have led to mimicry by other non-toxic butterflies. Danaid Egg-fly (Hypolimnas misippus), Great Egg-fly (Hypolimnas bolina), and Common Mime (Chilasa clytia), mimic Plain Tiger (Danaus chrysippus), Blue-spotted Crow (Euploea midamus) and Tiger type Danaids respectively. The “toxic-like” appearance of those that mimic others will deter predators from eating them.

Blue Tiger (Tirumala limniace)

Common Mime (Chilasa clytia)

Plain Tiger (Danaus chrysippus)

Danaid Eggfly (Hypolimnas misippus)

Danaid features
As we all know, insects have three pairs of legs, but the forelegs of Danaids have been receded and packed close to the thorax. Although Danaids seem to fly in gentle and powerless ways, they have extremely high-flying ability, and most can fly long distances.

Most male Danaids have hair-like “pencils” on their abdomens, which release scents to attract females. In addition, on the wings of the male, there are androconia — modified scales that also release sex pheromones to attract the opposite sex.

Danaid pupae are usually yellowish green, enabling camouflage amidst foliage. Many species also have pupae with metallic colours, such as jewel-like flashes; and in some species, the whole pupa is suffused with metallic lustre, while others have only metallic spots. The metallic colour can deter predators, reflect light, help the pupae hide.