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Madeline Phillips, Carlton, Christopher E.
Ixodes scapularis, or the Eastern blacklegged tick, is a common tick species in the eastern and midwestern United States. Unfed (unengorged) adults are dark brown to nearly black in color and vary from 2 mm to 4 mm in length, depending on sex, with females generally larger than males. Females are usually more reddish in color, and males are darker brown. As the common name suggests, the eight legs are nearly black. Engorged females may reach 12 mm in length and are dark gray. Blacklegged tick nymphs are smaller versions of adults, around 1 mm in length. Larvae, which are referred to colloquially as seed ticks, possess six legs and are less than 1 mm in size. Eggs are minute and laid in clusters of many thousands in surface debris such as leaf litter. They look like tiny clusters of caviar.
Blacklegged ticks go through three basic life stages (instars) after hatching from eggs: larva, nymph and adult. This species requires a different host for each of the life stage (three host ticks). The typical life cycle for this species requires around two years. Eggs are deposited in ground debris during late winter to mid-spring and larvae hatch that summer. Larvae use a technique called “questing” to detect their first host, which is usually a rodent or small bird. Questing behavior involves positioning on the edge of a leaf or blade of grass and extending the front legs until a passing host gets close enough for the tick to crawl onto. Questing is utilized in all instars. Blacklegged ticks remain in the larval stage until the following spring, when they molt into nymphs and seek a new mammal host. During the following fall, the tick reaches adulthood and must find another new host, which may be a small or mid-sized mammal, including humans. Mating occurs, and the females lay eggs during the following spring. Blacklegged ticks and brown dog ticks (Rhipicephalus sanguineus) are active in winter in Louisiana.
The blacklegged tick is a significant veterinary and medical species because of its ability to transmit a wide variety of diseases across species. This species rose to notoriety after it was discovered to be the leading vector of Lyme disease during the early 1980s. In addition to Lyme disease, blacklegged ticks also vector babesiosis and Powassan disease, which are also serious illnesses. Lyme disease is caused by Borrelia burgdorferi. It was first isolated in 1982 and has been of increasing concern due to apparent increases in infection rates. Some of this apparent increase may reflect improved surveillance and documentation methods.
Monitoring and prevention. Surveying for ticks by specialists is usually done by flagging, which documents tick species and relative abundance. Flagging utilizes a piece of cloth attached to a handle that is waved through foliage or dragged along the ground. Ticks detect the movement, attach to the cloth and are then collected, identified, preserved and deposited into collections as vouchers. Collection efficiency can be enhanced using carbon dioxide in the form of dry ice as an attractant. For certain ticks such as the blacklegged tick, walk sampling can be effective in surveying for ticks. Walk sampling, as the term suggests, uses walking and wearing light colored clothes to sample ticks across a transect.
Individuals walking in tick-infested habitats should frequently and thoroughly check their bodies for ticks. Larval ticks (seed ticks) can be difficult to detect initially and can rapidly inflict large numbers of bites on exposed skin. Ticks are able to secrete an anesthetic in salivary secretions, so the initial bite may go unnoticed for hours or even days. In addition, ticks secrete a cement-like substance that locks them in place until properly removed or feeding is complete. Removing blacklegged ticks within the first 12 hours is crucial to minimize disease transmission. Wearing long pants and high socks can minimize tick access to bare skin, and treating clothing with high percentage formulations of DEET or pyrethroid based insecticides appropriately labeled for clothing treatment is more effective in deterring ticks. Always follow label directions when applying repellents or clothing treatments of insecticides. Individuals experiencing an unusual rash around a tick bite or flu-like symptoms following a bite should seek medical attention. Early detection improves chances of full recovery.
Natural control. In residential situations, especially in rural surroundings, tick populations can be managed by keeping lawns cut short, keeping shrubbery away from homes and buildings, and treating pets with appropriately labeled tick prophylactic formulations. Maintaining awareness of tick seasonal cycles of activity and species occurring in the vicinity can also contribute to avoiding bites.
Chemical control. Perimeter sprays using pyrethroid based formulations labeled for ticks can reduce populations in small areas, but no effective control for large areas of tick habitat is available.
Contact Us: For advice about pest identification or diagnosis, contact the LSU AgCenter Department of Entomology. Reach the department through the Contact Us webpage.
P4018
9/16/25
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Adult female Ixodes scapularis (Scott Bauer, U.S. Department of Agriculture, Bugwood.org, Creative Commons 3.0).
Male (lower) and female (upper) Ixodes scapularis (Gary Alpert, Harvard University, Bugwood.org).
Engorged Ixodes scapularis (Scott Bauer, U.S. Department of Agriculture, Bugwood.org).
