Why are most insects that are dangerously vemonous/poisonous colorful?
In: Biology
To scare off predators in the case of poisonous. It would be better to advertise you’ll kill anything that eats you rather than get eaten. It acts as a deterrent.
As for venomous creatures, often they’re not colourful, think black mambas or comodo dragons. They are hunters and don’t want to advertise they’ll kill you.
It’s called aposematic signalling- basically a big, dramatic display that warns others that you’re toxic/taste bad/are otherwise nasty to mess with.
Interestingly, it’s common for distantly related species to converge to have a similar aposematic pattern/appearance. If both/all parties are actually noxious/dangerous, it’s called Mullerian mimicry. If one species is actually safe and tasty, but *looks* like a noxious species, it’s called Batesian mimicry.
The very good reason is that being poisonous isn’t very useful if your predator only finds out after they’ve eaten you. It’s much better if the predator looks at you and instinctively thinks “I don’t want to eat that” and thus doesn’t eat you and you get to live.
The bright colors do this. Most animals hide from predators so they use dull colors or ones that blend in with their surroundings. This works great until they’re seen. If instead you’re bright red and yellow you’ve given up hiding in the hopes that the predator will see those colors and not care that they’ve found you.
A great example of this is the Monarch Butterfly. It’s a bright orange and black butterfly that while it’s a caterpillar feeds on milkweed. Milkweed has cardenolides which are chemicals that defend against most herbivores and parasites but a few species specialized in eating it, the Monarch being one.
So this butterly grows up eating poison so that they too are sort of poisonous. Animals eat butterflies but when they (some not all aniamls) eat a monarch they don’t like it.
So while the Monarch species evolved to eat (and thus reproduce around) milkweed nearby species evolved to not each monarchs. Instincitve or learned you eat one monarch you don’t eat other monarchs. Not great for that individual monarch but good for the species as a whole.
Further the Viceroy butterfly evolved to mimic the pattern of the Monarch. The Viceroy isn’t poisonous and doesn’t eat milkweed, instead it just developed a similar black and orange pattern so that the animals that learned not to eat monarchs wouldn’t eat them either.
It’s about large scale behavior. You bet on your predator having learned not to eat things that look like you because they had bad experiences with them in the past.
When the poisonous insect first evolved the toxin it probably wasnt at a lethal level yet. If a predator ate them they would get sick but not die. So the predator would remember that bug and try to avoid it later. This avoidance is easier if the bug has a distinct and colorful appearance. So suddenly it’s a big advantage to be both toxic and colorful, since you are now less likely to get eaten. So they became more and more colorful over time. The fact that they are toxic reinforces this primal instinct to avoid eating colorful bugs in predators. If a predator doesnt have this instinct, it would eat the bug and die.
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