Ixodes scapularis
Black legged tick
(Also: Northern deer tick)

The geographic range of Ixodes scapularis, the deer tick or blacklegged tick, consists of North America as a whole, also known as the Nearctic region. The climate in this region is favorable for their definitive host, the deer, and therefore they can be found in most areas of the United States occupied by deer. This includes the eastern coast of the United States, westward towards Texas, and northward into Minnesota. These ticks are also found in southeastern Canada, and northern Mexico, but it is very rare to find I. scapularis past these borders. (Rand, et al., 2003; Wilson, et al., 1985; Rand, et al., 2003; Wilson, et al., 1985)

Ixodes scapularis is a non-nidiculous tick species. In the larval state, the tick feeds on a variety of mammals and birds, but most prevalently the white-footed mouse. As the tick becomes an adult, it feeds mainly on large mammals, primarily white-tailed deer.

Habitat and microclimates are still crucial in the establishment and survival of this tick species. Even in areas of high deer population, the deer tick may not be found. Moving towards 175 m elevation, populations decline. In addition to elevation, coastal proximity is important. Ixodes sculparis seems to thrive in humid environments, and may also be assisted through dispersal by neotropical songbirds that are migrating in/through the area. (Anderson and Magnarelli, 1980; Rand, et al., 2003; Wilson, et al., 1985)

Ixodes scapularis is approximately 3 mm in length. Females have a black head and dorsal shield, and a dark red abdomen. Males are entirely black or dark brown. Both sexes have eight legs that are black. This black legged tick also has a characteristic anal opening, which appears within a horseshoe-shaped ridge on the lower edge of the abdomen, on the ventral side. Deer ticks, unlike other ticks, do not have festoons (ridges on the edge of the lower abdomen).

In the larval state, the nymph has a dark head, with a translucent body. Like the adult, the nymph has four pairs of dark legs, but is smaller, measuring at about 1-2 mm in length. ("Protect yourself from ticks and lyme disease", 1997)

Ixodes scapularis is a three-host tick, meaning that each stage of development reattaches to a host.

Eggs are deposited in the spring, and hatch in the summer. Starting in June, eggs deposited earlier in the spring hatch into tiny larvae. The larval activity is at its highest intensity in August, when larvae attach and feed on a wide variety of mammals and birds, but primarily on white-footed mice, Peromyscus leucopus.

After three to five days of feeding, engorged larvae leave their first host and drop to the ground where they remain through the winter and most of the spring. After this period, larvae molt into nymphs, which feed on a variety of hosts, generally small mammals, for three to four days. As is the case with the larvae, engorged nymphs detach and drop to the forest floor where they molt into an adult. This adult stage becomes active in October and remains active through winter days. Adult female ticks feed upon their definitive host, the white-tailed deer, for five to seven days while the male tick rarely feeds at all. Ixodes scapularis mates upon its host, with the male dying shortly after copulation. Once through the winter, engorged adult females typically lay eggs on the forest floor after they have detached from their white-tailed deer host. (Anderson and Magnarelli, 1980; Troughton and Levin, 2007)

Mate-finding and courtship behavior in Ixodes scapularis is largely regulated by pheromones, chemicals produced by one organism that attract other organisms. These pheromones cause ticks to aggregate on the ground, host, or vegetation. This causes contact between the sexes.

The deer tick is polygynous, with the female mating with one male, and males mating with as many females as possible. Generally the males inseminate 2-3 times. While males may attempt to mate with females who have already mated, there is a system in place to stop other males from mating with already inseminated females. Mating can take place on either the host, or vegetation in their region. (Kiszewski and Spielman, 2002; Kiszewski, et al., 2001; Yuval, et al., 1990)

While ejaculatory pheromones are used by many other tick species, they have not yet been found in Ixodes ticks. Males require a set of cues to inseminate the female. Without such cues, males will either self-abort copulation within a few minutes of engagement or will remain in copula for hours or days without delivering a spermatophore. Insemination does not necessarily follow courtship in these ticks.

Ixodes ticks continue their intercourse even after the transfer of sperm. Ixodes scapularis males require less than one hour to inseminate the female, however the mean time of copulation is about 2.5 hours. (Kiszewski and Spielman, 2002; Kiszewski, et al., 2001; Yuval, et al., 1990)

The male Ixodes scapularis dies after it has completed mating with one or more females, and the female dies after laying eggs. As such, there is no parental investment after fertilization. (Kiszewski and Spielman, 2002)

Ixodes scapularis lives approximately two years in the wild. Its life cycle is dependent more on reproduction than predation due to the tick's smaller size which is undetectable by birds. Males generally die after mating with one or more females, while females die after laying their eggs. Therefore, Ixodes scapularis lives until reproduction. Other effects on lifespan are density-independent such as temperature and humidity changes. (Kiszewski and Spielman, 2002)

Ixodes scapularis is a solitary species, growing, molting, and feeding by itself. The main interaction this species has with other deer ticks is during mating.

To find hosts Ixodes scapularis uses an "ambushing" approach. This "ambushing" is done by waiting on vegetation or the ground until its host brushes against the ticks position, generally catching its legs, allowing it to grasp on and continue its feeding or on-host mating. (Carroll, 2002)

Potential mates communicate through aggregating pheromones. Otherwise, Ixodes scapularis is a solitary tick and does not communicate with other species. (Kiszewski, et al., 2001)

Larval ticks of the Ixodes scapularis feed once on the blood of white-footed mice, or other small mammals. As they progress through the life cycle, nymphal ticks continue to feed on the blood of white-footed mice and other small mammals, sometimes moving to raccoons or medium sized mammals. After the final metamorphosis, female adult ticks feed on the blood of larger mammals, such as deer. Males do not feed on blood, but instead live only to mate.

In each of the life cycle states, Ixodes scapularis feeds only once, for 3-5 days. (Anderson and Magnarelli, 1980)

Ixodes scapularis is very rarely affected by predators. Due to its small size, this tick is rarely targeted or found by birds or other possible predators. Instead, it is highly affected by density-independent factors such as climate with temperature and humidity changes. (Bertrand and Wilson, 1996; Matthewson, 1984)

Ixodes scapularis is parasitic throughout its life on the white-footed mouse, small mammals and birds, and the white-tailed deer. In addition to being a parasite, I. scapularis is also a vector of Lyme disease, caused by Borrelia burgdorferi. This tick is also known to be a vector of human babesiosis, Babesia microti, and human granulolytic erlichosis. (Des Vignes and Fish, 1997)

There is no known positive economic importance for humans.

Ixodes scapularis is a vector of Lyme disease, caused by Borrelia burgdorferi. Lyme disease can be debilitating to humans by causing fatigue and ultimately problems with the central nervous system. Ixodes scapularis is also known to be a vector of human babesiosis, Babesia microti, and human granulolytic erlichosis. (Des Vignes and Fish, 1997)

Due to the high population of deer in the northeastern United States, the deer tick has not become endangered in any manner. The species is thriving in it's current habitats.