Several different factors can help to identify the species of a tick, including size, color, the length of its mouth parts, location and time of the year. Although there are many different species of ticks, these factors are usually quite reliable in determining the specific species.
The first factor to look for is the shape and color of the tick's shield, also known as a scutum. Each species of tick has a different shape and color or pattern on its scutum. For instance, those belonging to the Ixodes genus, which includes deer ticks, typically have a solid-colored brown or black shield, while most other genera have uniquely patterned shields. Although these factors are easier to see if the tick hasn't eaten, it is usually still possible to spot the signs even on an engorged tick.
Size can also help to determine the species of tick, as most dog ticks are larger than deer ticks. Another factor that can help identify a deer tick is the lack of festoons, which are small grooves that are found on the back of all other species. Looking at the length of the mouth parts may also help, as dog ticks and other Dermacentor ticks have much shorter mouths than the other groups. The location and time of the year should also help identify the species, as only certain species are active during given times of the year.