We had an outreach event this past weekend, with tons of cool insects and arthropods. One of the coolest was this whip scorpion (in the order Thelyphonida). Their other common name (and this is awesome) is vinegaroons.
Though they have eight legs like other arachnids, they use only six for walking (like an insect!) and the front two have been modified into antennae-like sensory organs. Their pincers out front are modified pedipalps, which on spiders are the additional appendages near the mouth that help them shove food in there. They are segmented just like the other legs. (Interestingly, wikipedia chimes in: “They are traditionally thought to be homologous with mandibles in Crustacea and insects, although more recent studies (e.g. using Hox genes) suggest they are probably homologous with the crustacean second antennae.”)
Unlike true scorpions, whip scorpions don’t have venom and a stinger. Instead they spray acid at enemies! One of the acids they spray is acetic acid, giving them the name vinegaroon.
Kind of cool dudes!