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Blacklegged Tick

​Ixodes scapularis

Blacklegged tick.jpg

Left to right: larva, nymph, male, female

Why should you check for ticks?

Pennsylvania ranks number one in the country for reported Lyme Disease cases. Additionally, the Blacklegged tick can potentially pass other pathogens to humans and make us sick. Removing a tick quickly can reduce the risk of contracting a tick-borne disease.

What do they look like?

Blacklegged ticks vary in size depending on the life stage. Adult females are the largest with adult males being slightly smaller. Nymphal Blacklegged ticks are about the size of a poppy seed while the larvae are slightly larger than the head of a pin. Due to their small size, the nymph stage is implicated with the majority of Lyme Disease transmission.  

A tick on a poppy seed bagel for size comparison

Blacklegged tick life cycle

The life cycle of these ticks generally spans two years. They go through four life stages (egg, larva, nymph, and adult) in this time. Once the egg hatches, each subsequent life stage must have a blood meal to survive. Each life stage finds a new host to receive its blood meal. Blacklegged ticks can feed from mammals, birds, reptiles, and amphibians.

Graphic showing the lifecycle of a blacklegged tick

Image source: CDC

Where are they found?

The Blacklegged tick is found in the eastern half of the United States. Adult ticks can be found in forest edge habitat and understory vegetation throughout winter when temperatures are above freezing. However, the greatest risk of being bitten is spring, summer, and fall from a nymph or adult female. Nymphs and larvae are most active in the summer months and are found in leaf litter. 


Image source: CDC

Peak activity periods of Blacklegged tick life stages


How can you get sick from a Blacklegged tick?

Blacklegged ticks feed on multiple hosts during their life cycle. Each feeding increases the risk of contracting a pathogen (ex. white-footed mouse with Lyme Disease). Some of the pathogens can remain in the tick after subsequent molts. When a tick takes a blood meal from a human, infection may occur. Most Lyme transmission occurs in June and July due to the activity and small size of the nymphs.

What pathogens are found in Blacklegged ticks?

The causative agent of Lyme Disease, Anaplasmosis, Babesiosis, Ehrlichiosis, Deer Tick Virus, and Hard Tick Relapsing Fever have all been found in Blacklegged ticks collected in Pennsylvania.


Infections acquired through the bite of a Blacklegged tick are treatable, especially if you catch it early. Many people with these infections report never seeing a tick. Likely they go unnoticed because these ticks are so small. See your doctor if you experience any symptoms consistent with tickborne illness and have spent time outdoors.

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