Question Series: Butterfly Senses

How do butterflies taste, smell, or touch/feel?  What do they see?  Can they hear?

I am frequently asked these questions and don't always know how to answer.  Since I have never had any classes on butterfly biology, what little I know has been gleaned from various sources over the years, so this post is a compilation of what I know and have learned from researching these questions today.  For example, I never thought much about whether a butterfly could hear sounds, I knew they could feel vibrations, but I just learned that some butterflies actually have "ears" on their wings!  Who knew?

Sight

Adult butterflies have large compound eyes that provide them with an almost 360 degree range of vision.  They see the full color range including ultraviolet light, and they see polarized light which allows them to orient in relation to the sun even in cloudy weather.  Many flowers have patterns that are invisible to our unaided eye, but are visible under ultraviolet light.  When these flowers are viewed under ultraviolet light, "nectar guides" appear, where the center of the flower is often colored completely different than the rest of the flower.  This feature also guides bees and other nectar- and pollen-feeders.  An example of this can be seen here and many other websites by doing a search for "ultraviolet flower patterns".

Caterpillars, on the other hand, have very limited vision that is mostly a detection of light and dark.

Touch

Sensory hairs all over caterpillars and adult butterflies provide its sense of touch.  These hairs are mostly on the body and head of adults and larvae, but some are also located on an adult's antennae.  Some larvae communicate to each other with clicking or drumming that produces vibrations that others feel.

Smell

Butterflies smell with their antennae, palps, and some other parts of their body covered with sensory hairs.  They can detect pheromones and host plants sometimes over a mile away.

Taste

Butterflies have special receptors in their feet that allow them to taste host plants and flowers.  Have you ever noticed a butterfly perched on a leaf or flower and seemingly pawing the air with their legs, repeatedly scraping the leaf surface?  It's their version of licking food to see if tastes right!  Females are known to detect appropriate host plants to lay their eggs on by "tasting" the plant with their feet.

Hear

I am just learning about how this works, so if anyone reading this has more information or corrections, please comment on this post to let me know.  From what I've read, not all butterflies have "ears", but more are being discovered.  The most well-known examples are the tropical Crackers (Hamadryas) and Longwings (Heliconius), but the Blue Morpho was discovered to have ears that detect low- and high-pitched sounds.  The "ear" is a tiny membrane-covered sac at the base of the wing (like having an ear in your shoulder).  Many night-flying moths are also known to be able to detect the acoustic pulses of bats, but I'm not going to go into that here, maybe for another post!

What you always wanted to know about butterflies

In two weeks (Labor Day weekend) I'll be giving a series of 10-15 minute butterfly presentations at the Kittitas County Fair.  I plan to talk about which butterfly species people can find locally, and other information about butterflies in general.  If anyone reading this has any questions you've always wondered about butterflies or moths, please comment on this post to let me know.  I would like to do a series of posts related to this, so any suggestions would be great!  Some potential topics:
Flight (how do they fly, how far, etc.)
How does temperature affect them?
What do the adults eat?
Also, I'll talk about some common misconceptions, such as:
Touching a butterfly's wings will kill it
All moths fly at night

(not quite north)west butterflies

Last week I was in San Diego for a work conference, and was happy to see a few butterflies hanging out in the grounds around the convention center and along the waterfront.  I wasn't able to photograph any of them, so this post will be a bit boring, but I wanted to make a quick report.
One Monarch, possibly two (lost sight of one, saw another shortly after in a slightly different spot).
Giant Swallowtail, my first one in the wild! I've seen a few in tropical butterfly houses, but never wild.
Black Swallowtail, one that liked hanging out in a little green space between the hotel and convention center.
Fiery Skipper, a few males and a couple dozen females in several places along the waterfront, most in a lawn where I saw some females ovipositing (really wish I had my camera at that moment!)
Cabbage White, about a dozen decorating the flowers in Seaport Village
a sulphur of some kind, medium-sized, not sure if it was a dogface, orange sulphur, or something similar.
something gray-blue, most likely a hairstreak.

waving goodbye, a sea lion on a floating dock at the pier near the USS Midway

Arctic Blue - Plebejus glandon

Another interesting little butterfly that can be found on the Sinlahekin Wildlife Area is the Arctic Blue, Plebejus glandon.  They were first discovered there in 2006 by another butterfly surveyor, at approximately 2600' elevation.  This was a record low elevation in Washington for this species that is usually only found above 5000'.  In 2008 I found another one about a mile down the road at 2400' elevation, and this year I found these two (photos below) at the same location as the original sighting in 2006.  So far we have only seen males, but we believe the females must be high up in the rocky slope above the road, close to their hostplant which is also yet to be confirmed.  Larvae of this species are known to feed on plants in the Saxifrage family, but without climbing the nearly vertical rock slope, it will be very difficult to determine exactly where these butterflies are coming from and what they use as their larval host.

Arctic Blue Plebejus glandon - males, dorsal and ventral

Introducing: Sonoran Skipper

Here are the official photos of the newest member of the Sinlahekin Wildlife Area butterfly family!  This cute little guy has a wingspan of 26 mm.  Remember the "wing terminology" post from last month?  Notice the large black patch on the forewings in the photo below? That is the stigma, which indicates this is a male butterfly.
The Sonoran Skipper (Polites sonora) is very similar to but more common than the Mardon Skipper (Polites mardon), a Washington State Endangered Species and a Federal Candidate Species.  The wings of the Mardon are more "stumpy", the forewings being smaller in proportion to the hindwings than the Sonoran Skipper.  Both species fly low to the ground and resemble large houseflies buzzing about, so they often go unnoticed.  Larvae of these species feed on grass, primarily fescue (Festuca sp.).

For more information about the Mardon Skipper, start with the Butterfly Conservation Initiative website, and a quick Google search will point you to many other resources.