Friday, September 12, 2008

The case of the missing legs: brush feet

Insects have 6 legs, so why do some butterflies like Zebra Longwings seem to only have 4 legs?

Zebra Longwings is a species of butterfly belonging to the Nymphalidae family of butterflies. Also known as brush-footed, these adult butterflies have a first pair of legs that is very reduced in size giving them the appearance of having only 4 legs instead of 6. They also have caterpillars that tend to be spiky and chrysalids with shiny spots.

The Nymphalidae family is broken into 5 clades. Greek for "branch", clades are a taxonimic group for species that derive from a common ancestor. The 5 clades of the Nymphalidae family are libytheine (Snout butterflies), danaine (milkweed butterflies like the Monarch and Queen), satyrine (which includes Morphos), heliconiine (such as Zebra Longwings) and nymphaline (a sister group to heliconiine that includes Emperors). This family includes about 5,000 individual species that bear the four-footed look of Nymphalidae.
Image: Clinton & Charles Robertson from Del Rio, Texas & College Station, TX, USA (Wikimedia Common)


2 comments:

Carolyn said...

Hey Kristen,
Are the brush feet an adaptation for Nymphalidae to eat pollen?

Kristen said...

Not really. Zebra Longwings and a few other species of closely related heliconian butterflies are the only known butterflies to be able to consume pollen. The collect the pollen on their proboscis but I am not sure the brush feet are used to assist this process. I'll look into it.