Quoted By:
Venonat regardless doesn't evolve into a cocoon because it is an adult moth, just sexually dimorphic. Most moth lines reference this, by being two staged, and having either stage be a flightless, sometimes rotund, adult, and sometimes specifically never progress beyond a cocoon stage like with the bagworms.
Another key point with the japanese pokedex classifying Venomoth as a dokuga moth in the japanese pokdex, which has come to mean the tussock family of moths. This ties it with Venonat being the stage out of either line that is covered in venomous, rash-causing hairs. Dokuga could also be directly referencing brown-tailed moths, which share with depictions of Venomoth having spots, washed-out/grayer wings and body, and brown abdomen
Butterfree is specifically a Great Mormon butterfly that has its eyespots reworked to be its face. The dark coloration of the Great Mormon beyond the eyespots also lends itself to Butterfree's body and feet. This is not unlike what Caterpie does with the eyespots of swallowtail caterpillars in general. Metapod also plays with the idea of false heads and facial features with how it has a different facial expression depending on the angle you look at it.
If you want DEEPEST LORE, a Great Mormon is red in the first place to be mimic other butterflies, signaling either its own toxicity or the toxicity of other butterflies. This is an explanation as to why Butterfree is still known to poison opponents, not be full blown Poison type, while still resembling something that actually is in Venonat.
nah jk it's literally shitty genwun design recycling, durr when will they fix the mixup between blue serpents and orange dragons lul
