Nymphs - are the size of a poppy seed. They are biege, sometimes appearing transparent with a dark head. Adults - are the size of a sesame seed. Adults are active all winter long, as long as temperatures are above freezing. Adults feed primarily on deer, but will also attack cattle, horses, dogs, etc.
Human beings are accidental hosts.
All stages have distinctive features that separate tick species. Deer ticks do not have festoons. Other common ticks do have festoons. It tends to be in the center of the body of most ticks. On the deer tick, the anal opening is near the lower edge of the abdomen AND is surrounded by a horseshoe-shaped ridge.