In the Aligned continuity, yes indeed there are many Arachnicons. ^u^ And being the lover of spiders I be, I saw fit to make a sketch of an average, everyday Arachnicon (from Tarn). They're apparently not as common as ordinary fliers and ground-based and et cetera types, but they do appear. ^u^ And they are not all bad guys! (Phooey on you, Airachnid. XP Psycho.)
Lookit this fine and friendly feller. X3 Look at allllll the arms he's got to hug with. Champion huggers, these mechs.