SUB-PHYLA: Trilobitomorpha: Myriapoda: Cheliceriformes: Crustacea: Hexapoda: Trilobites (extinct) Centipedes Spiders, scorpions Crustaceans Insects ~1,000,000 species so far... Compound eye with many facets spiracles Insects decouple gas exchange and circulation - air moves in through spiracles, little holes in the cuticle - piped directly to each cell of the body through a system of tubes (like air ducts) for efficient delivery of oxygen - overcomes inefficient open circulatory system... Batesian mimicry Monarch caterpillar eats milkweed plant, stores toxic chemicals which make adult butterfly taste bad to predators Who is related to whom? Who is related to whom?