Structural features of Insects vs Spiders?

[LiL Homie]

What are 2 structural features that make insects different then spiders?

I think this is one:
1- Antennae- for sensing touch/smell.
2- ? I was thinking wings, but not all insects have wings... Is the fact that they have 3 body segments a good one?

Please let me know if I'm on the right track. My book doesn't go over this stuff thats why I'm having a tough time finding these. I would appreciate any help. Thanks.

[kjle]

1. I'm not sure. I think it works, but number of legs may work better.
2. Yes.

[SU_reptile]

Arachnids:
- they have prosoma (cephalothorax; 7 segments) and opistosoma (abdomen 12 segments in spiders)
- they have only simple eyes
- they have chelicerae and pedipalpi
- they never have wings
- they usually breathe book lungs
- they have 4 pairs of locomotive limbs
- they have no larvae and so - simple development
- they can spin a spider-web by means of appendages placed on their abdomen
- they have specific sensory organs other than insects

Insects:
- they have head (6 segments), thorax (3 segments) and abdomen (6-12 segments depending on position in systematics)
- they have a pair antennae, mandibles, labrum and labium that are modified complex of appendages called maxillae. All appendages I mentioned together are called mouthparts
- they have about 6 types of modifications on mouthparts that plays different roles
- they may develop wings
- they may have simple eyes and complex eyes
- they usually breathe tracheae or specific organs adaptated to breathe under the water (I'm not sure if they may be called gills in English)
- they have complicated development with a few generations of larvae that are different in various groups

Those are only examples. I don't remember many things from invertebrates (which I hate by the way). Hope it will be helpful