September 26, 2012

Clearwing Butterflies

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A clearwing butterfly feeds on a flower full of pyrrolizidine alkaloid toxins. Photo by Phil Torres.



A common sight in Tambopata- Clearwing butterflies, known as the Ithomiini, are beautiful, deadly, and a bit confusing to scientists. Find out more:

Why are they clear?
  • Most butterflies have scales on their wings which result in their color. If you rubbed off those scales, the wings would look clear.
  • Clearwing butterflies mostly have scales along their wing veins, and lightly throughout the rest. 
  • If you can imagine a clear butterfly flying in the shadowy understory of the Amazon, it makes quite a difficult target to follow, protecting them from predators like birds.

Why are they deadly?
  • Unlike most butterflies that are poisonous, clearwings to not eat a poisonous plant as a caterpillar to incorporate it into the adult stage.
  • Instead, these butterflies actually seek out poisonous flowers with pyrrolizidine alkaloids in them as an adult to obtain this toxin (see above image).
  • Pyrrolizidine alkaloids are known to cause damage to livers, and can cause death in some cases.

What is an Ithomiine Pocket?
  • One of the most interesting thing about these butterflies is that they form ‘pockets’ in the forest in which dozens of clearwings of different species all roost for the night in one distinct area.
  • This can be observed around 4pm, in which clearwings are slowly all flying around each other getting ready to roost, and at night, when the butterflies have all settled on low hanging branches or vines.
  • It is still unknown why they do this, but one theory says it serves as a sort of dry-season ‘jail’ when climactic conditions aren’t favorable. 
  • However, I have observed very large ithomiine pockets in rainforests without dry seasons and with consistent rain, so they is likely another underlying cause as well.

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