Ticks are arachnids, meaning they are closely related to mites and spiders. They have four life stages: egg, larvae, nymph and adult. Unfed ticks are flattened, teardrop shaped. Larval ticks have six legs, while nymph and adult ticks have eight legs. Three tick species are a human health concern in New York: the blacklegged tick (deer tick), the lone star tick, and the American dog tick.
Tick size depends on the species, life stage, if the tick has fed and how long it has fed. Larval ticks hatch from an egg, develop into a nymph, then into an adult. For the blacklegged and lone star ticks, larvae are about the size of a grain of sand, nymphs about the size of a poppy seed, and adults about the size of a sesame seed. When fully fed, an adult female blacklegged and/or lone star tick can be as large as a raisin. American dog ticks are larger than blacklegged and lone star ticks.
Depending on the species, life stage and gender, ticks show different shapes and color patterns. Tick abdomens expand after feeding, making identification difficult for most people. If you need to know the species of a tick, consider having it professionally identified (see sidebar).