Number of segments in a grasshoppers head?
There are 3: the vertex, the occiput, and the fastigium.
Arachnids and insects both have segments. Arachnids have two segments- a head-chest region called the cephalothorax and also an abdomen. Insects have three segments- a head, a thorax, and a abdomen. The second thing they have in common is joints. If you need more information you can go to Animal Diversity Web.