Ticks are arachnids belonging to the sub-class Acari, which includes both mites and ticks. Over 80 species of ticks have been identified in the U.S. These can de divided into two families: the hard ticks (lxodidae) and the soft ticks (Argasidae). Both families are associated with the transmission of diseases to humans, but the members of the hard tick family are more frequently encountered in and around homes.
Within the family of hard ticks, there are several species referred to as “wood ticks” that are of key importance due to their frequent interaction with humans in the outdoor environment and the transmission of some serious diseases. Among them are the black-legged tick (deer tick), the Rocky Mountain spotted fever tick (Dermacentor anderson), American dog tick (Dermancentor variabilis) and the lone star tick.
The life cycle of the hard ticks involves 4 stages. It begins with the female laying eggs. Depending on the species, clusters of hundreds to thousands of eggs may be laid in protected cracks and crevices, which develop into six-legged larvae. The larvae will then crawl to a place where they may brush up against a passing host. The larvae will crawl onto the animal and begin feeding on its blood. Feeding takes a matter of days before the larvae are fully engorged, at which time it drops off the animal. Several weeks later, the larvae molt and emerge as nymphs. At this time, the nymph climbs again onto a similar site where it waits for the next host animal and repeats the process. The final instar nymph molts into an adult. The adult is capable of waiting significant periods of time before feeding, in some cases 6 to 9 months. Once the adult female has attached to and fed from a host, she then detaches and can only then begin to lay eggs.
Ticks spend most of their time waiting to attach to a host animal in a process called questing. Ticks can't fly or jump, so they are dependant on their hosts coming to them to provide a meal. In order to take advantage of these opportunities, ticks will climb up the stems of tall grass, weeds or other suitable objects and wait patiently for a passing mammal to brush up against them. Ticks can sense a suitable host by detecting chemical cues-especially carbon dioxide, vibrations, and motion. When they sense a host approaching, they hold out several of their legs and cling to it as it passes by or they may simply drop from a perch onto the host.
Ticks have been implicated in vectoring many diseases to humans. Rocky Mountain Spotted Fever, Relapsing Fever, Lyme Disease, and Encephalitis are among the more serious. The real danger from ticks arises from the hosts they choose during the early stages of their life cycle. In many cases, they feed on animals which are reservoirs of diseases. Such is the case for the Black-Legged tick whose larvae and nymphs feed on the blood of the white-footed mouse, a known reservoir of Lyme Disease, then commonly vector this disease to humans. A well-executed tick control program and common sense measures of avoiding tick bites go a long way in reducing the hazards ticks pose around the home.