How do you tell the different between a spider bit other bits?

Insect Bites: Determine the size of the bites. Spider bites are largest, and on average are about the size of a dime. Mosquito bites are small, generally the size of your pinky fingernail. Fleabites are the size of the head of a pin. If you've been bitten by a tick, you won't be able to locate a bite, but you will find a small black fleck that resembles a mole.

See below: Hard to tell oftentimes. Many insect bites look alike. However, spider bites, upon close examination may present with two central fang marks, otherwise, local reactions from insects look very similar to each other.