Contrary to other arthropods, most crustaceans have 2 pairs of antennae and biramous legs (each leg having 2 “branches”, an endopod and an exopod); however, both of these characters are actually ancestral and have just been secondarily lost in myriapods and hexapods, just like gills.
Since crustaceans are a grade rather than a branch, and because you are emphasizing leg numbers in insects and arachnids, maybe you could use “Decapods” instead of “Crustaceans” as a branch that is sister to insects. Decapods are a very diverse and monophyletic order of crustaceans that includes all of the familiar crabs, lobsters, shrimp, prawn, etc. (but not things like copepods, barnacles, waterfleas, and ostracods, which are less familiar to most people); they can be characterized by having 5 pairs of “walking legs”, although one or more of these pairs may be modified into pincers or even paddles.
The big problem with this image to me is that the animal you have labeled a “Crustacean” is actually a horseshoe crab! Despite their name, horseshoe crabs are not crustaceans, but a type of arachnid or a close relative of arachnids, depending on which taxonomist you ask. Horseshoe crabs do have gills, but their gills are different in structure from crustacean gills.
I would also add some segmented worms to the list of “Who has it”, and depending on how much you go into evolution, maybe emphasize that gills have evolved multiple different times. Otherwise it seems good.
Oh, that is a big issue yes. Thanks for so graciously pointing that out. I definitely had thought that a horseshoe crab was a crustacean. Thanks for clarifying! I will make those changes. I appreciate your insight a lot!
When talking about evolution, both of these things pretty much mean the same thing! It’s like how birds came from dinosaurs, so birds are a type of dinosaur. Insects came from crustaceans, so insects are a type of crustacean - we just don’t usually think of them that way.