see
Explanation
This comic is a meta-joke about the nature of comic strip characters and vision.
In the panel, one character says "Betsy, did you see that?" Betsy replies, "I wouldn't say 'see.' I would say 'detect.'" This is already a funny bit of pedantry -- correcting someone's casual use of the word "see."
The "Fun Fact" caption below explains the joke more fully: "Comic strip characters don't have mammalian vision, but rather rely on primitive eyespots for predator detection." This is a reference to real biology -- many simple organisms (like flatworms or jellyfish) have eyespots rather than complex eyes. Eyespots can detect light and dark but can't form images, so they're useful for detecting predators (shadows passing overhead) but not for "seeing" in the way mammals do.
The comic humorously applies this biological concept to cartoon characters, suggesting that since comic strip characters are drawn as simple figures (often with dot eyes), they don't have real mammalian eyes and therefore can't truly "see" -- they can only "detect." It's a playful, self-referential joke about the art form itself, treating the simplified visual representation of comic characters as a literal biological limitation.