imho spiders end up being fascinating for having a bunch of wierd/cool traits all lumped together:
- hydraulic limb extension, but muscular limb contraction
- extremely multi functional silk
- limb regeneration
- anti-freeze protiens give some species super-cooled body fluids in winter
- intrincate unique to each species interlocking pedipalp and genital shapes
- venom + venom injection systems
- inability to ingest solids
- TONS of variation in hunting methods between diff species