Wood Ticks

What Is It?

The American dog tick (Dermacentor variabilis), commonly known as the wood tick, primarily lives in forests and grassy areas west of the American Eastern Seaboard. Along with the Rocky Mountain wood tick, American dog ticks are one of the most common species of ticks found in the United States. Wood ticks reside in large numbers throughout New England, especially in wooded backcountry.

What Does It Look Like?

american dog tick
female american dog tick
female dog tick
source: UFL.edu

Wood ticks fall into the animal class of arachnids, which means they possess eight legs. The overall appearance of the insect is dependent on sex, in most cases. Sexual dimorphism, or the marked difference in appearance between the sexes of a certain species, often influences the size and color of ticks from males to females.

The female wood tick generally features a mostly dark-brown body with a small, light-brown band called a scutum, or shield, sitting dorsally near the head. Males also feature a scutum, similar in color, spanning a majority of the arachnid’s back. Female specimens often appear larger in size. The arachnid looks mostly the same in appearance throughout each stage of life, although wood tick larvae only possess six legs. Ticks gain a fourth pair of legs during the nymphal stage.

dog tick size, image credit: ufl.edu

The bodies of ticks expand as they feed. A typical wood tick measures roughly one-quarter of an inch for females and slightly less for males. Engorged after feeding, the bodies of wood ticks may expand up to a half-inch in length. The scutum of the tick remains as the body fills with blood, which gives the shield a more forward appearance as opposed to just resting on the back of the arachnid.

 

What Do They Feed On?

Wood ticks feed on the blood of mammals. Adults generally feed on dogs as well as deer, cattle, horses, and humans. Wood tick larvae and nymphs use smaller mammals, like rats or mice, as feeding hosts. The arachnids need at least one host per life stage in order to survive.

What Dangers Does it Present?

Wood ticks present serious health hazards for human beings. While mammals common to wooded areas generally play host to ticks for feeding, wood ticks regularly attach to humans who spend time in parks, fields, or other grassy, wooded areas. The serious health threats imposed by the arachnids to humans exist in the form of infectious diseases.

Lyme Disease

Ticks are known to spread the bacteria known as Lyme disease, which causes fever, vomiting, and diarrhea, affects the central nervous system, and often results in disabling effects if untreated. Wood ticks are also known to cause paralysis in animals, predominantly canines, due to a toxin released in the saliva while feeding.

Removal of ticks takes special care, as too much direct contact with the fluids exchanged while the arachnid feeds may result in the accidental transfer of the toxin to the eyes or mouths of humans and may cause temporary or potentially permanent remote paralysis.

quick tick removal
click to enlarge

Rocky Mountain Fever

Wood ticks feed only from mid-March to mid-July; so that is the only time humans can contract this disease. Symptoms of Rocky Mountain spotted fever begin with a rash within 2-5 days of being bitten. The rash appears on the wrists and ankles. This disease can be deadly. Wood ticks can also transmit tick paralysis and other painful diseases. If you are bitten by a tick and suspect Rocky Mountain spotted fever, seek medical attention immediately.

Life Cycle

The full maturation of a wood tick takes several months to complete. The process begins with fully engorged females laying egg sacks developed while feeding.

Eggs

Females often lay as many as 6,500 eggs at a time. Wood tick eggs take between a month and a month and a half to hatch.

Larva

The newborn larvae must find a host to blood feed to initiate the change into a nymph. Feeding often lasts two weeks at the larval stage. Digestion of the initial blood meal causes molting that sometimes lasts as long as seven days.

Nymphs

Nymphs must also find hosts to feed in order to progress into the adult stage. Feeding at the nymphal stage lasts around 10 days and concludes with digestion of the blood meal and molting of nymphal exoskeletons, which sometimes lasts up to several months. Wood ticks typically mate on host animals. Females die soon after laying eggs.

Wood ticks are a three-host tick, which means they need to feed off of a different host in the various stages of their lives. Females will feed until they are fully engorged, while males will feed and then look for a mate. After the mate is found, they return to feeding.

How They Move

Ticks have no means of locomotion except crawling. Since they feed on hosts that are much larger than they are, ticks must climb up tall weeds or fences to wait for their food sources. Ticks locate their prey through vibrations or odors, jumping on to the host when it passes by.