Tuesday, April 30, 2013

Lepidoptera Vocabulary Lesson II: Chrysalis vs. Cocoon

Nothing bugs a lepidopterist quite like hearing this statement: "Oh, look at all the butterfly cocoons!" We hear it dozens of times a week here in the Flight Encounter. Of course, we smile and politely correct the guest, but all the while we're cursing well-meaning books like The Very Hungry Caterpillar which give out bad information. It's time to clear things up once and for all: butterflies don't make cocoons.


Here's a little more information:

Metamorphosis is the process in which an organism grows and changes, characterized by rapid and dramatic changes in form. In other words, an organism that undergoes metamorphosis doesn't just get bigger, it also changes its looks in a very obvious way at least once during the process. In insects, there are both complete and incomplete types of metamorphosis; butterflies and moths undergo complete metamorphosis, with four stages.

The third stage of complete metamorphosis is the pupa (pronounced "pew-pah"), the stage of life between caterpillar and adult. The process that takes place during this stage is the same for both butterflies and moths, but the terms used to describe them at this point are different. Without getting overly technical, here's what you need to know:

  • Chrysalis: A butterfly in its pupal stage is properly called a chrysalis (pronounced "kriss-uh-liss"). This term technically refers to the hardened outer skin protecting the organism inside, but lepidopterists also use the term to describe butterfly pupae in general. The proper pluralization is “chrysalides”, although “chrysalises” is also acceptable. 
A variety of butterfly chrysalides
  • Cocoon: The definition of cocoon is very specific: it is a protective silken case woven around a pupa. Butterflies do not weave extra protective coverings around their pupae, so "butterfly cocoon" is incorrect. Lepidopterists use the term "cocoon" only when referring to certain moths that do weave these protective coverings. A cocoon can vary from very fine and delicate to a harder shell mixed with organic materials, depending on the species of moth. (Not all moths weave cocoons; in these cases, the proper way to refer to the organism at this stage is simply as a pupa.)
Cocoon of an Isabella Tiger Moth. The pupa itself is wrapped in the protective silk case.
It's pretty simple, really: don't use the word "cocoon" when talking about butterflies. If in doubt, just call it a "pupa" at this stage - that's correct no matter what's inside. 

NOTE: Eric Carle, author of the beloved book The Very Hungry Caterpillar, has addressed fans' questions about the inaccuracy of the info in his book. Click here to read his statement.

No comments:

Post a Comment

We welcome your participation! Please note that while lively discussion and strong opinions are encouraged, the MOSI BioWorks Butterfly Garden reserves the right to delete comments that it deems inappropriate for any reason. Comments are moderated and publication times may vary.