While many people had all these crazy ideas on the harvest these concept art images do indeed show
that it is a covenant creation. The reasoning for it's odd looks is due to it being covered in rock and rust which hides it's true design.Here you go
It does indeed look more bug like at the same time the legs clearly look like the scarab's, which is what i originally pointed out. Anyway,we now know it isn't anything other than the covenant so please spread this around.