What are the differences between butterflies and moths?

Butterflies, skippers and moths all belong in the insect order Lepidoptera. Worldwide, there are five families of butterflies and one family of skippers, which share some specialised similarities in body form. All of these families are present in Australia. Moths form a larger group of 125 families worldwide. In Australia, 82 families of moths are represented.

However, there are some overall rules that can be used to tell a moth from a butterfly or skipper. Note that there are always exceptions to each 'rule'.

Antennae

Moths: Have simple thread-like or 'feathery' antenna without a club
Butterflies and Skippers: Have a thickened club or hook on the tip of the antenna, never 'feathery'
Exceptions: Several families of moths have antenna with clubs, most notably the Castniidae (Sun Moths)

Colour

Moths: Duller colours
Butterflies and Skippers: Brighter colours
Exceptions: Many moths are brilliantly coloured, especially day-flying ones such as the northern Queensland Day Moth Alcides metaurus (Uraniidae), or the Jacob's Coat Moth Agarista agricola (Noctuidae). Many butterflies and skippers are dark brown with few markings.

Wings

Moths: Wings are linked together with a bristle-like structure called a frenulum
Butterflies and Skippers: Wings are not linked – no frenulum
Exceptions: Australia has the only skipper in the world with a frenulum, the Regent Skipper Euschemon rafflesia (Hesperiidae). Also, many moths do not have a frenulum.

Resting posture

Moths: Hold wings flat when resting
Butterflies and Skippers: Hold wings together above body when resting
Exceptions: Many moths, including geometrid moths hold their wings up in a butterfly-like fashion when resting. Butterflies in the lycaenid subfamily Riodininae, and skippers in the subfamily Pyrginae hold their wings flat when resting.

Forelegs

Moths: Forelegs fully developed
Butterflies and Skippers: Forelegs reduced, missing terminal (end) segments
Exceptions: Only some butterflies have reduced forelegs. Most skippers have normal forelegs.

Pupae

Moths: Pupae spin a cocoon
Butterflies and Skippers: Pupae (chrysalids) not in cocoon
Exceptions: Many moths do not spin a cocoon, many butterflies and skippers form a silken shelter, often with plant leaves.

Activity

Moths: Fly at night
Butterflies and Skippers: Fly during the day
Exceptions: A few butterflies and skippers are active at dusk, many moth species are day-flying.

Link

• Order Lepidoptera (Butterflies, Moths and Skippers)