All substances take up the least amount of volume in their (1.) solid phase, a little more volume in their (2.) liquid phase, and the largest amount of volume in their (3.) gas phase. The closer atoms or molecules get to one another, the less volume is occupied by the substance that they comprise.
A large, retrospective series examining human bite wounds in children found that none of the bites manifesting as abrasions became infected, while the rate of infection was much higher in bite wounds that caused punctures or lacerations.
A variety of mites are known to bite humans and cause irritation, itchy papules and rashes. Most of these mites are actually parasites of other animals not humans, but will bite humans when their normal hosts are not present. They are mostly nest parasites of birds, rodents and other animals.