Ticks are external parasitic organisms that feed solely on the blood of birds, mammals and some reptiles. Not insects, ticks are arachnids and, like spiders, have eight legs in the nymph and adult stages (their larvae possess only 6 legs). In North America, hard ticks (represented by more than 700 species worldwide) are the only group that parasitize mammals.
Hard ticks mature through a three year life cycle. Adult females lay their eggs in the soil by late summer or early fall; these hatch into larvae which overwinter in the soil and attach to their first host (a bird or small mammal) in the spring. By late summer or early fall, the larval tick drops from its host and molts to a nymph (a small replica of the adult), which overwinters beneath dead vegetation or leaf litter, surviving on engorged blood; the nymph repeats this cycle the second year, generally using a larger host and molting to an adult by autumn. Adult females emerge in spring and attach to large mammals (cattle, goats, deer, humans) to feed and mate; the adult males do not feed during their spring/summer phase and die off after mating. Once the adult female lays her eggs, she also dies, generally by mid autumn.
The number and diversity of tick species are greatest in tropical regions, decreasing toward colder and drier regions of our planet. They locate hosts by waiting on tall grass or other vegetation, jumping to or grabbing the host as it passes by; this behavior is often noted by hikers who become festooned with dozens of ticks after crossing a meadow or using an overgrown trail. Unfortunately, ticks are vectors for a wide variety of rickettsial, viral and bacterial infections (including tick fever, ehrlichiosis, Rocky Mountain spotted fever, Lyme Disease, meningoencephalitis and tularemia, among others) and should be removed as soon as possible. Ticks, themselves, are consumed by birds and reptiles and are victimized by parasitic wasps.
