From the Super Mario Wiki
Skeeters are giant 4-legged bugs that float on top of the water that are first introduced in Super Mario 64. They appear in several 3D Mario games, each with their appearance changed. Skeeters can also walk on land as well as skate on water. Skeeters are based off a real-world insect known as the water strider.
Super Mario series
Super Mario 64
In Super Mario 64, they are seen on the painting of Wet-Dry World and also are enemies floating aimlessly on the water in Wet-Dry World and Dire Dire Docks. They look like big blue spiders that plate webbings on their feet and an antennae on its back. If defeated, they release three Coins. In Wet-Dry World, they can be lowered onto a platform. When they see Mario, they get mad for him taking them off the water, and home in on him.
In Super Mario 64 DS, Skeeters are found in the same places as in Super Mario 64, but are blue with yellow-tipped legs, the angler on their head is red instead of orange, and they have black eyes here. Three Coins are again released for their death. Again, they only home in on the heroes if they are lowered onto land.
Super Mario Sunshine
Skeeters reappear in Super Mario Sunshine, but they are referred to as Pondskaters in this game. They follow a similar design to their Super Mario 64 cousins with sharp tipped legs, but don't retain their tails. They are found in Bianco Hills. When jumped on, Mario propels upward to a height rivaling the Rocket Nozzle. Also, they are resistant to F.L.U.D.D., as spraying them only made them stop moving for a very short while. The only way to defeat them was to bring a Yoshi onto a lilypad and eat them.
New Super Mario Bros.
Skeeters make another reappearance in New Super Mario Bros., but they receive another overhaul in appearance; they are now fat and red, instead of gangly-legged and blue. They appear in two levels, 3-A and 8-2. They skate aimlessly across the water, and drop Skull Bombs that pass through blocks and destroy them. The Skull Bombs, as a result, can give access to two Star Coins (one normally, and one mini pipe, which held one). They and their Skull Bombs release Coins if hit with a fireball from a Fire Flower. Only the red part of their bodies can damage Mario or Luigi.
Super Mario Galaxy 2
Despite not appearing in the prequel, In Super Mario Galaxy 2, Skeeters re-appear with another overhauled appearance. They now have a flat, purple body, anglers absent and are found in the Cosmic Cove Galaxy. They always home in on Mario, and can be stomped for a Coin or hit with a spin to release three Star Bits. They also appear in Starshine Beach Galaxy and Throwback Galaxy.
Mario Party 3
Names in other languages