A fuzzy yellow caterpillar with black spikes on top of its back sort of like stegosaurus dinosaur spikes on its back can someone tell me what they are. i have never seen any pupas on our porch or on the roof. i think its cause they get eaten by spiders or praying mantis's. but its yellow i live in washington state. its fuzzy spiny with black on its back. not monarchs or swallowtails i know for a fact. but someone tell me what these things are.
The two most likely suspects are the yellow-based tussock moth (Dasychira basiflava; Lepidoptera: lymantriidae) and the banded tussock moth (Halysidota tessellaris; Lepidoptera: Arctiidae). See http://www.richard-seaman.com/Arthropods/Usa/Caterpillars/NorthernIllinois/Yello... and http://www.hubbardbrook.org/image_library/images/Banded%20Tussock%20Moth.JPG, respectively