Fun & Learning With Butterflies
A few days ago I posted this one:
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As identified previously, it is likely that this is an Eastern Tiger Swallowtail.
After some research (and a bit of common sense on my end in terms of seeing this one with its partner), I can further identify this as a (likely)
male Eastern Tiger Swallowtail.
That's because, nearby, was another butterfly...which at first I could not identify:
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The blue detail of this dark butterfly (5D Mk III + 100-400 II @ 400) amazes me...
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But after reading this:
The coloration of animals is an interesting study. One of the stranger aspects is the fact that creatures which are similar and lead similar lifestyles can be remarkably different in
www.yoursun.com
...it turns out the dark butterfly is most likely a
female Eastern Tiger Swallowtail!
From the link (between the XXXs):
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Some female tiger swallowtails occur in a black color phase, which looks very much like a black swallowtail.
But why though? According to the laws of natural selection, all organisms are shaped by their environments. Those that are a poor fit are less likely to survive long enough to reproduce. So what is it that has caused these butterflies to adopt such strikingly different color patterns? As adults, they share the same general habitat, the same predators, the same food sources.
As it turns out, you have to look at other species to make sense of the puzzle. There is another butterfly, the pipevine swallowtail, that is also black with blue iridescence. Pipevine swallowtails are named for the food they eat as caterpillars — toxic plants in the
Aristolochia genus. These toxins remain in their bodies even as adults, making them distasteful to birds and many other predators.
Now it makes sense. Black swallowtails, black phase tiger swallowtails, and a handful of other related species all benefit from a resemblance to their poisonous cousin. This is similar to the more familiar situation in which the monarch butterfly, which gets its toxicity from milkweeds, is imitated by the perfectly edible queen and viceroy butterflies. This type of imitation is called Batesian mimicry, and there are lots of Batesian species complexes out there.
OK, mystery solved! Except — if imitating a toxic relative is such an effective strategy, why aren’t all tiger swallowtails black? In some areas, most females are black, but not all. And males always have those easily seen bright yellow wings. Hmmm …
There’s another force at work here: Sexual selection. If you outfox your predators but can’t find a mate, then your genes don’t get passed on to the next generation. And that’s what happens with some of the black phase tiger swallowtails. Even though dark females still act just like other tiger swallowtails, and even though they produce the same pheromones, males just aren’t as interested in them. These guys are apparently traditionalists and prefer the good ol’ yellow and black that their species is known for.
XXX
One more female Eastern Tiger Swallowtail...
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...and surely a wise (and snarky!) CR reader can make (up) some connection between butterfly mating and human mating