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Northern Black Widow (Lactrodectus variolus)

Detailing the physical features, habits, territorial reach and other identifying qualities of the Northern Black Widow

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The Northern Black Widow shares a lot in common with its southern cousin, including a painful bite that only feels worse, meriting an urgent visit to the doctor.

Updated: 05/13/2023; Authored By Staff Writer; Content ©www.InsectIdentification.org
The glossy, black abdomen of the Northern Black Widow is dotted with large red circles on the dorsal (back) side. A split, or 'broken', red hourglass is clearly visible on the ventral (belly) side. Noting that separation between the top and bottom the hourglass is important. It is different from the solid, one-piece hourglass seen on the more widely-recognized Southern Black Widow. The 'broken' hourglass means the spider is NOT a Southern Black Widow. The venom of both types of Black Widow females is toxic, but the Northern Black Widow's is less so. Only females are harmful; males are slightly different in pattern and are considered harmless.

Mortality from a bite by a Northern Black Widow is about 1% of all victims, with most of those fatalities being small children. Any bite from a Northern Black Widow merits a visit to a physician as it is difficult to gauge how toxic the spider's venom is at the time of the bite and how each individual will respond to it. (A spider that recently emptied venom into an insect will have less venom in a bite given soon after that.) All bite victims experience immediate pain, and it increases in intensity for hours afterward. It usually subsides in a day. Other symptoms include sweating, fever, nausea, rapid heart rate, and weakness. A physician can help ease the immediate discomfort a victim feels and monitor the patient for other symptoms until a full recovery is made.

This species of spider forms tangled, messy webs in woodlands, stone and wood piles, and undisturbed corners of sheds, garages and other shelters outside. It is not aggressive and does not actively seek to bite people. The Northern Black Widow is shy and more apt to try and hide. If startled or threatened, which can happen when a person suddenly turns over the log or stone the spider is sitting on, it bites in defense. Sightings of this species are somewhat rare as it is active at night and less likely to be seen during daytime. If spotted, treat it as a dangerous spider and keep your distance.©InsectIdentification.org

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General Characteristics

Capability, Shape, Texture/Pattern, Benefits, Dangers
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Harmful insect icon
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Taxonomic Hierarchy

Species Breakdown
Kingdom: Animalia
  Phylum: Arthropoda
    Class: Arachnida
      Order: Araneae
        Family: Theridiidae
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          Genus: Lactrodectus
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            Species: variolus

Identifying Information

Size, Colors, Features
Scientific Name: Lactrodectus variolus
Category: Spider
Size (Adult; Length): 4mm to 11mm (0.15" to 0.43")
Colorwheel Graphic Colors: black; red; orange; white
Descriptors: biting; painful; venomous; harmful

Relative Size Comparison

Typical Size Between 4mm (0.2in) and 11mm (0.4in)
Lo: 4mm
Md: 7.5mm
Hi: 11mm

Territorial Map*

U.S., Canada, and Mexico
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Prince Edward Is.  
* MAP NOTES: The territorial heat map above showcases (in red) the states and territories of North America where the Northern Black Widow may be found (but is not limited to). This sort of data is useful when attempting to see concentrations of particular species across the continent as well as revealing possible migratory patterns over a species' given lifespan. Some insects are naturally confined by environment, weather, mating habits, food resources and the like while others see widespread expansion across most, or all, of North America. States/Territories shown above are a general indicator of areas inhabited by the Northern Black Widow. Insects generally go where they please, typically driven by diet, environmental changes, and / or mating habits.
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