Monday, March 21, 2016

Not Just Straws: My New Understanding of How Butterflies Eat

A few years ago, on one of my first blog posts about butterflies, a commenter asked me whether butterflies that ate mostly nectar had different mouthparts than did butterflies that preferred rotting fruit. At the time I didn’t know for sure, and all the information I could find did not differentiate between species. So I said I thought they all were pretty much the same. In fact it was pretty difficult to find images showing the mouthparts of different butterflies... Until now!

Last month I was delighted to find a blog post on this very subject. It turns out I was wrong, the mouthparts do vary depending on a butterfly’s preferred food source.

I already knew that a butterfly eats through its proboscis, a coiled up tube that is actually made from two mouthparts fused together. The generally accepted way that a proboscis works is like a straw, to suck up liquid.

However, sipping liquid through the straw is not the only thing going on. In fact, it turns out butterflies also have little sponge-like tissues, called legulae, at the end of the proboscis that allow them to absorb nutrients from mud or other sources that aren’t already liquid. It’s this sponge that varies between nectar eaters like Tiger Swallowtails, and non-nectar eaters like Commas.

Even a butterfly that frequents flowers, like this Tiger Swallowtail, can also absorb salts and minerals from mud by using the legulae at the tip of its proboscis.

This Eastern Comma, on the other hand, never visits flowers at all. It has different legulae to absorb minerals from rotting fruit and dung as well as mud.

In fact, some butterflies even eat blood. A friend of mine once watched butterflies flock to the open wound on a dying turtle, and told me how horrific she found it to see these graceful creatures take life from the turtle in its last moments! Yikes.

So, Hannah, I finally found the answer to your question. Butterflies do have different mouthparts depending on what they like to eat. I’m sorry I couldn’t find this in time to be relevant for you, but perhaps you’re still out there looking for the answer. In that case, please go over to Ask An Entomologist  to see some amazing microscopic photographs of different mouthparts. The original paper is also located here if you want to check that out too.

I love learning new things, even if I get proved wrong in the process!

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