Thursday, April 14, 2016
Imagine you are a bird and an orange butterfly speeds past you. You ate an orange butterfly once and it made you sick, but you don’t know if this is the same kind of butterfly. You have to make a snap decision about whether or not to eat it, and you have to do it quickly. Chances are, you would avoid this butterfly on the off chance it was the same toxic butterfly you tried to eat before.
Over 100 butterfly species have flown in our Tropical Butterfly House since it opened in 1998. At any one time, we probably have more like 30 butterfly species represented, and it can be challenging just to identify that many, especially when they are flying. Some butterflies stand out and are readily distinguishable, but others are more difficult to identify because they look so much alike. One such group, the tiger wing complex, does not look alike by chance; they look alike because they are mimics.
When I first started working at Pacific Science Center, nearly four years ago, it took me a long time to realize how many tiger wing butterfly species we had; for a while I thought that they were all the same butterfly, when in actuality, we typically have at least four orange and black butterfly species at any given time. I wanted to get better at identifying them, but it was difficult to identify from photographs alone because they didn’t show scale and some details get lost. I decided that I wanted to make a shadow box with these butterfly species for our staff to use, but first I wanted to learn more about mimicry.
Mimicry is when two or more species, which share a superficial resemblance, but are otherwise not necessarily closely related, gain advantage from their similarity. In the case of butterflies, the most typical advantage to gain somehow helps them to avoid predation. Mimicry is different from camouflage because the butterflies are not blending in, they are standing out. There are two different types of mimicry, both of which are prominent in the world of butterflies.
Batesian Mimicry is when one butterfly evolves to share a similar appearance to another butterfly which is inedible or poisonous to predators. The butterfly might be delicious, but birds and other predators mistake it with the noxious butterfly. Predators are less likely to eat any butterfly that looks like that again, so butterflies which share that appearance are more likely to pass their genes on to the next generation. One example of Batseian mimicry in butterflies is the poisonous Monarch butterfly, Danaus plexippus, and its non-poisonous mimic the Viceroy, Limenitis archippus, a species we don’t fly in our Tropical Butterfly House.
Müllerian Mimicry is when two or more species evolve to look alike, and all are unpalatable or poisonous to predators. Since a bird might confuse the first orange butterfly it tries to eat with all other orange butterflies, it is likely to avoid eating ALL orange butterflies in the future. This behavior is reinforced if it tries to eat two different orange butterfly species, and has the same experience twice. All orange butterflies benefit from looking like each other and tasting bad and/or being poisonous because they spread the word to predators. The tiger wing complex is an example of Müllerian Mimicry; they all look alike, and they are all inedible.
After researching mimics, and collecting some specimens, I felt more confident with my ability to distinguish them, and started to put together the shadow box. I decided to use a clear shadow box so that we could easily view the dorsal and ventral side of their wings. I chose the five butterflies we get most often and have the most difficult time differentiating.
As a guest of our Tropical Butterfly House, if you see a tiger wing butterfly, take a moment to look at the details and compare the differences. You might find out that you have seen many more butterfly species than you first thought!