The swallowtail butterfly, Papilio xuthus, only feeds on select members of the citrus family. How does the female butterfly discriminate host from non-host plants? Swallowtail butterflies use chemotaxonomy, the chemicals present in a plant. The Xuthus Swallowtail “identifies” its host plant by a mixture of 10 chemicals present in the plant leaves.
Like most insects the “taste” receptors that identify the plant chemicals are on its legs. The legs are a much more convenient location for taste receptors than the mouth, because the butterfly can get information about a plant as soon as it lands. As it walks from plant to plant, it “tastes” the plant chemicals. If taste receptors were confined to the mouth, lowering the mouthparts to taste every plant would be much less convenient.
Human taste receptors are typically classified as “salt” “sweet”, “sour” and “bitter”. In the Swallowtail, some of the “taste” receptors are more specific than generic “bitter”. These receptors respond preferentially to one or only a few chemicals that are associated with the butterfly host plant. The genes and receptors of Swallowtails are under study*. These studies may lead to improvements in biosensors that can detect important chemicals in our environment.
A) Leg of Xuthus Swallowtail Butterfly
B) Close up of Taste Receptor Hairs on the Leg (arrows).
Image: Ryuda and Colleagues, J Neurosci
*Gustatory Sensing Mechanism Coding for Multiple Oviposition Stimulants in the Swallowtail Butterfly, Papilio Xuthus. Masasuke Ryuda, Delphine Calas-List, Ayumi Yamada, Fre ́de ́ric Marion-Poll, Hiroshi Yoshikawa, Teiichi Tanimura, and Katsuhisa Ozaki. J. Neurosci., January 16, 2013 • 33(3):914 –924
DOI:10.1523/JNEUROSCI.1405-12.2013
It is interesting how insects’ taste receptors can be even more specific than taste receptors in humans. This post fits directly in with the lectures we have had in class about sensory receptors.
I think it’s interesting how all these insects taste their food! To have evolved in such a practical manner as to be able to readily tell if what they land on is edible or not… I have some friends that could use that kind of ability…
Can you imagine if people had taste receptors on their limbs like bugs do? That’d be terrible!
This blog is very interesting to me. Learning the instead of the swallowtails taste receptors being in their mouth they are on their legs. The reason why is kind of crazy too to me just because it is more convenient for them. But if you really think about it they are in a perfect spot for the swallowtail.
I found this blog very interesting! I had no idea that insects had taste receptors on their legs. It is crazy to think that it is even possible for them to have taste receptors there due to the fact that humans have their taste receptors in their mouths.
I always wondered why, when at a picnic or something, flies would just land on the food and kind of sit there for a while. It also seems to be convenient for them to have taste receptors on their legs so they can keep their heads up in case there is danger coming. I’m glad with how much I am barefoot that I don’t have taste receptors on my feet.
I never knew this much about insects. I thought they were just like humans, but we are totally different– Insects are more interesting! Having taste receptors on their legs and feet, just imagine if we had the same thing- I would be even more picky than I am today! Humans and insects have both adapted in two completely different ways. Eating with our hands is more convenient for us as taste receptors on their feet is from them. Just Awesome!
This post really interested me in the way that the insects have taste receptors on their legs. No wonder why the flies and butterflies often land at the food or plants a lot. I just thought they are having some rest on it. It was surprising to me that they can actually walk and taste at the same time.