Blacklegged (Deer) Tick

blacklegged tick larva, nymph, adult male and adult female

Overview

Blacklegged ticks (a.k.a deer ticks) take 2 years to complete their life cycle from eggs and larvae in one calendar year to nymphs and adults in the next. This tick is encountered predominately in deciduous forest as well as tall grasslands and shrubs bordering forest edges. Their distribution relies greatly on the distribution of their reproductive host, white-tailed deer. Both the poppy seed-sized nymph stage and the larger adult female stage are responsible for transmitting diseases such as Lyme disease, Babesiosis, and Anaplasmosis.

Blacklegged Tick Nymph stage growth comparison
Adult female blacklegged Tick growth comparison

Field Notes

Adult males and females are active October-May, as long as the daytime temperature remains above freezing. Preferring larger hosts, such as deer, adult blacklegged ticks can be found questing about knee-high on the tips of branches of low growing shrubs. Adult females readily attack humans and pets. Once females fully engorge on their blood meal, they drop off the host into the leaf litter, where they can over-winter. Engorged females lay a single egg mass (up to 1500-2000 eggs) in mid to late May and then die. Larvae emerge from eggs later in the summer. Unfed female blacklegged ticks are easily distinguished from other ticks by the orange-red body surrounding the black scutum. Males do not engorge and, although infected like the female, they are not involved in transmitting infections. Males are frequently found coupled with females, mating even off-host.

female and male
blacklegged tick

Life Cycle Stages

Select a region to see how seasonal activity and diseases carried by this tick change across the country.
  • Larva

    blacklegged larva tick
    Top
    underside of a larval blacklegged tick
    Bottom
    • Northeast Central Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      • Hard tick relapsing fever

        Borrelia miyamotoi (bacteria)

    • Southeast Central Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      No known diseases in this region at this time.
    • Mid Atlantic Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      • Hard tick relapsing fever

        Borrelia miyamotoi (bacteria)

    • New England Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      • Hard tick relapsing fever

        Borrelia miyamotoi (bacteria)

    • South Atlantic Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      No known diseases in this region at this time.
    • Northwest Central Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      No known diseases in this region at this time.
    • Southwest Central Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      No known diseases in this region at this time.
  • Nymph

    blacklegged nymph
    Top
    underside of a nymphal blacklegged tick
    Bottom
    • Northeast Central Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      • Hard tick relapsing fever

        Borrelia miyamotoi (bacteria)

      • Human Anaplasmosis

        Anaplasma phagocytophilum (bacteria)

      • Human Babesiosis

        Babesia microti (protozoa)

      • Lyme Disease

        Borrelia burgdorferi (bacteria)

      • Powassan virus

        Powassan virus lineage II (flavivirus)

    • Southeast Central Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      • Hard tick relapsing fever

        Borrelia miyamotoi (bacteria)

      • Human Anaplasmosis

        Anaplasma phagocytophilum (bacteria)

      • Human Babesiosis

        Babesia microti (protozoa)

      • Lyme Disease

        Borrelia burgdorferi (bacteria)

      • Powassan virus

        Powassan virus lineage II (flavivirus)

    • Mid Atlantic Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      • Deer Tick virus

        Flavivirus Powassan virus lineage

      • Hard tick relapsing fever

        Borrelia miyamotoi (bacteria)

      • Human Anaplasmosis

        Anaplasma phagocytophilum (bacteria)

      • Human Babesiosis

        Babesia microti (protozoa)

      • Lyme Disease

        Borrelia burgdorferi (bacteria)

      • Powassan virus

        Powassan virus lineage II (flavivirus)

    • New England Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      • Deer Tick virus

        Flavivirus Powassan virus lineage

      • Hard tick relapsing fever

        Borrelia miyamotoi (bacteria)

      • Human Anaplasmosis

        Anaplasma phagocytophilum (bacteria)

      • Human Babesiosis

        Babesia microti (protozoa)

      • Lyme Disease

        Borrelia burgdorferi (bacteria)

      • Powassan virus

        Powassan virus lineage II (flavivirus)

    • South Atlantic Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      • Hard tick relapsing fever

        Borrelia miyamotoi (bacteria)

      • Human Anaplasmosis

        Anaplasma phagocytophilum (bacteria)

      • Human Babesiosis

        Babesia microti (protozoa)

      • Lyme Disease

        Borrelia burgdorferi (bacteria)

      • Powassan virus

        Powassan virus lineage II (flavivirus)

    • Northwest Central Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      • Hard tick relapsing fever

        Borrelia miyamotoi (bacteria)

      • Human Anaplasmosis

        Anaplasma phagocytophilum (bacteria)

      • Human Babesiosis

        Babesia microti (protozoa)

      • Lyme Disease

        Borrelia burgdorferi (bacteria)

      • Powassan virus

        Powassan virus lineage II (flavivirus)

    • Southwest Central Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      • Hard tick relapsing fever

        Borrelia miyamotoi (bacteria)

      • Human Anaplasmosis

        Anaplasma phagocytophilum (bacteria)

      • Human Babesiosis

        Babesia microti (protozoa)

      • Lyme Disease

        Borrelia burgdorferi (bacteria)

      • Powassan virus

        Powassan virus lineage II (flavivirus)

  • Adult Male

    made blacklegged tick
    Top
    underside of a male blacklegged tick
    Bottom
    • Northeast Central Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      No known diseases in this region at this time.
    • Southeast Central Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      No known diseases in this region at this time.
    • Mid Atlantic Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      No known diseases in this region at this time.
    • New England Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      No known diseases in this region at this time.
    • South Atlantic Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      No known diseases in this region at this time.
    • Northwest Central Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      No known diseases in this region at this time.
    • Southwest Central Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      No known diseases in this region at this time.
  • Adult Female

    female blacklegged tick
    Top
    underside of an adult female blacklegged tick
    Bottom
    • Northeast Central Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      • Hard tick relapsing fever

        Borrelia miyamotoi (bacteria)

      • Human Anaplasmosis

        Anaplasma phagocytophilum (bacteria)

      • Human Babesiosis

        Babesia microti (protozoa)

      • Lyme Disease

        Borrelia burgdorferi (bacteria)

      • Powassan virus

        Powassan virus lineage II (flavivirus)

    • Southeast Central Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      • Hard tick relapsing fever

        Borrelia miyamotoi (bacteria)

      • Human Anaplasmosis

        Anaplasma phagocytophilum (bacteria)

      • Human Babesiosis

        Babesia microti (protozoa)

      • Lyme Disease

        Borrelia burgdorferi (bacteria)

      • Powassan virus

        Powassan virus lineage II (flavivirus)

    • Mid Atlantic Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      • Deer Tick virus

        Flavivirus Powassan virus lineage

      • Hard tick relapsing fever

        Borrelia miyamotoi (bacteria)

      • Human Anaplasmosis

        Anaplasma phagocytophilum (bacteria)

      • Human Babesiosis

        Babesia microti (protozoa)

      • Lyme Disease

        Borrelia burgdorferi (bacteria)

      • Powassan virus

        Powassan virus lineage II (flavivirus)

    • New England Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      • Deer Tick virus

        Flavivirus Powassan virus lineage

      • Hard tick relapsing fever

        Borrelia miyamotoi (bacteria)

      • Human Anaplasmosis

        Anaplasma phagocytophilum (bacteria)

      • Human Babesiosis

        Babesia microti (protozoa)

      • Lyme Disease

        Borrelia burgdorferi (bacteria)

      • Powassan virus

        Powassan virus lineage II (flavivirus)

    • South Atlantic Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      • Hard tick relapsing fever

        Borrelia miyamotoi (bacteria)

      • Human Anaplasmosis

        Anaplasma phagocytophilum (bacteria)

      • Human Babesiosis

        Babesia microti (protozoa)

      • Lyme Disease

        Borrelia burgdorferi (bacteria)

      • Powassan virus

        Powassan virus lineage II (flavivirus)

    • Northwest Central Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      • Hard tick relapsing fever

        Borrelia miyamotoi (bacteria)

      • Human Anaplasmosis

        Anaplasma phagocytophilum (bacteria)

      • Human Babesiosis

        Babesia microti (protozoa)

      • Lyme Disease

        Borrelia burgdorferi (bacteria)

      • Powassan virus

        Powassan virus lineage II (flavivirus)

    • Southwest Central Region

      Encounter Risk

      Jan
      Feb
      Mar
      Apr
      May
      Jun
      Jul
      Aug
      Sep
      Oct
      Nov
      Dec

      Known Diseases Transmitted

      • Hard tick relapsing fever

        Borrelia miyamotoi (bacteria)

      • Human Anaplasmosis

        Anaplasma phagocytophilum (bacteria)

      • Human Babesiosis

        Babesia microti (protozoa)

      • Lyme Disease

        Borrelia burgdorferi (bacteria)

      • Powassan virus

        Powassan virus lineage II (flavivirus)