Biology of Bug-Type Pokémon

July 9, 2012

When it comes to Pokémon, three kinds of people exist: people who don’t know anything about them, 151ers, and people who have played more than just the first generation of games, red, blue, or yellow. (“151ers” refers to people who have only played the the first generation games and thus only know about the first 151 Pokémon.) If you are in the first category, you really are missing out on some great games, but if you are in either of the other categories, you know how truly pathetic bug-type Pokémon can be (though there are few worthwhile ones).

Metapod vs. Metapod

Currently there are 63 bug-type Pokémon, of which 15 are pure bug-types while the others are dual types (most commonly dual with poison or flying). While discussing the biology of ALL of the bug Pokémon may be out of the scope of this post, I do want to go over a few select cool ones that really show how well the writers thought about real world biology in creating these Pokémon, as well as a few obvious mistakes. Bug-types, though they are not my favorite to use, are some of the most interesting evolutionarily in all of the Pokémon games, making them some of my favorite to catch and collect. In this post, I will be focusing on a few choice bugs from the first generation of games. Stay tuned for future posts, where I will discuss other awesome bug-type Pokémon.


A truly beautiful evolutionary line that is probably one of my favorites. You have the ever adorable Caterpie, one of the cutest cartoon caterpillars of its time, which then evolves into Metapod. Metapod is the chrysalis stage (more on this in a moment) of the developing Caterpie/caterpillar, and as you can see from the video above, is a generally useless Pokemon, but is a means to an end. Because when it evolves, it becomes the beautiful Butterfree, which the animated show really did make a glorious moment of.

Metapod Evolves

Note how different this evolution was animated. Most evolutions in the show have the Pokémon turn white and glow, then change.

Its beauty though does come from how well it outlines the basic, holometabolous insect life cycle. This cycle involves a complete metamorphosis of the animal in its lifetime, and includes four stages: embryo, larvae (Caterpie), pupa (Metapod), and finally emerges (the technical term is eclose) to imago (Butterfree). They even go to pretty good detail making the pupa Metapod actually look like a monarch butterfly chrysalis. (They may or may not have actually been going for this, but monarch butterflies are usually the butterflies people think of first.)

The only issue is that Caterpie is not what a monarch butterfly larvae looks like, with Caterpie more closely resembling maybe the caterpillar of the polymorphous moth or the luna moth.

Note that the butterfly pupa is called chrysalis, which is distinct from the moth’s cocoon. In butterflies, the caterpillar starts its pupa stage by attaching itself to a tree via a small silk pad, and then sheds its skin revealing the pupa. Around the pupa is a hard chitin (pronounced KITE-in) based shell. Chitin is a macromolecule related to cellulose in plants, but is used to give fungi support, as well as used in crustacean shells. This whole thing, pupa and shell, is called the chrysalis. Moths on the other hand spin silk to wrap around themselves before the pupa stage, making a cocoon shell for protection. So only moths have cocoons.

While the Butterfree evolution series is incredibly well done, and made for a great teaching tool for the butterfly life cycle, the first generation of games had an analogous evolution series that made absolutely no sense whatsoever.


What a mess. First of all, Beedrill is clearly supposed to be a bee Pokémon, but while bees do have a typical holometabolous life cycle, the larvae and pupa spend their entire time in the beehive combs, fed and cared for by the adult worker bees. I’ve learned that this is apparently a recent evolutionary change as ancient animals in the family had caterpillar like larvae that moved around and ate leaves. But now they really are more like maggots, similar to flies.

Weedle is described to eat leaves and shoot a sticky silk like substance. Clearly they were going more for a moth-like life cycle, where the larvae are independent, spin silk to form a cocoon, and then emerge. Kakuna even looks fairly reminiscent of the brown moth cocoon!

I just don’t get why they would make the Caterpie/Butterfree evolution follow so closely with reality, but then make Weedle not evolve into a moth! And we all know how much cooler moths really are over butterflies.

You could argue that a final evolution moth is just not as scary or awesome as a final evolution bee (which I would actually agree with because bees are freaking awesome.) Or maybe just the idea of a moth Pokémon is super lame. Well the former can’t be true because Beedrill only has a base stat of 385 (where most gamers only use Pokemon with a score of at least 450), meaning it sucks. And the latter can’t be true because…


An even bigger mess. Here we have our moth. Strangely, I would argue in the first generation, this is probably one of the better bug type Pokemon; it has a base stat of 450 and is one of very few bug types to be a regular member of a gym leader/elite four member’s team (Koga). Yet this powerful moth, which would fit much better as the last evolution of Weedle and would dominate its rival bug type, Butterfree, evolves instead from Venonat, which is clearly supposed to be a gnat.

So instead of having any kind of biology, we choose to have a gnat turn into a moth. A gnat, which is an adult insect. A gnat, which is so distantly related to moths and has no similar appearance, size, behavior, or environment, turns into a moth. Incredible.

Stay tuned, as my next bug-type Pokémon post will focus on bug types beyond the first generation, including Combee-Vespiquen, Shedinja, and maybe others.



  1. Is it okay to put a portion of this on my personal web site if I submit a reference to this website?

    • That is absolutely fine. Thanks!

  2. […] my last Pokémon related post, I discussed some of the cool things the Pokémon creators did with the bug-types. Though there […]

  3. Very interesting info!Perfect just what I was looking for!

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