Spiders in Idaho: A Guide to the Most Common Species

Idaho is home to a diverse array of spider species. These eight-legged creatures can be found in forests, fields, gardens, and even inside homes across the state While some spiders get a bad rap, most are harmless and play an important role in controlling insect populations. This article will provide an overview of the most frequently encountered spiders in Idaho, how to identify them, and some interesting facts about their behaviors and habits.

Common Spider Families in Idaho

Several spider families account for many of the species found in the state. These include:

• Wolf spiders – Large, hairy spiders that hunt prey instead of building webs. Common wolf spiders in Idaho include the Tigrosa helluo and Hogna carolinensis.

• Jumping spiders – Compact, hairy spiders with large front eyes that jump on their prey. Some examples are the Bold Jumping Spider and the Zebra Jumping Spider.

• Orb weavers – Spiders that spin large, circular webs. The Banded Garden Spider and Western Spotted Orbweaver are commonly seen.

• Crab spiders – Spiders that resemble crabs and do not spin webs The Goldenrod Crab Spider ambushes prey on flowers

• Sac spiders – Pale nocturnal spiders that do not use webs to catch prey. The Western Yellow Sac Spider is often found in homes.

• Funnel weavers – Burrowing spiders that create funnel-shaped webs. The Barn Funnel Weaver builds its web in corners inside homes.

Venomous Spiders in Idaho

Only a couple of spider species in Idaho are potentially dangerous to humans:

• Western Black Widow – Shiny black spider with a red hourglass marking. Venom can cause severe muscle cramps.

• Hobo Spider – Fast-moving brown spider. Its venom is mildly toxic but rarely causes serious issues.

Most other spiders have fangs too small or venom too weak to cause significant harm to people. Bites may result in mild irritation or swelling similar to a bee sting.

Top 15 Common Idaho Spiders and How to ID Them

Below are descriptions of 15 frequently encountered spiders in the state to aid in identification:

1. Western Black Widow

• Jet black body with red hourglass on underside of abdomen
• Females reach 1/2 inch long while males are half that size
• Found in woodpiles and other sheltered spots outdoors

2. Hobo Spider

• Brown body with faded chevron patterns on the abdomen
• Grows up to 14mm long
• Often enters homes and builds funnel webs in basements

3. Zebra Jumping Spider

• Black and white striped pattern
• Compact body less than 1/3 inch long
• Uses jumping and excellent vision to capture prey

4. Bold Jumping Spider

• Stocky black body with bright patches of red, yellow, or orange
• Prominent front eyes and iridescent chelicerae
• Jumps on victims and injects venom without spinning webs

5. Banded Garden Spider

• Yellow or off-white body with black and white stripes
• Weaves large circular web with ziz-zag stabilimentum
• Up to 2 inches long with a round, oversized abdomen

6. Western Spotted Orbweaver

• Bulbous black and white patterned abdomen
• Weaves web with anchor lines radiating outward in a wheel-like pattern
• Less than 1 inch long with spiny legs

7. Goldenrod Crab Spider

• Yellow, white, pink, or green to camouflage with flowers
• Front legs extended to snatch prey off flowers and foliage
• Teardrop-shaped abdomen; smaller than 1/4 inch

8. Wolf Spider

• Patterned brown body with long spiny legs and large eyes
• Does not use webs to catch prey
• Carries egg sac attached to spinnerets

9. Grass Spider

• Brown or grey elongated body and legs with black stripes
• Spins sheet web near base of vegetation
• Very fast runners that chase down trapped prey

10. Western Yellow Sac Spider

• Greenish or pale yellow body with darker chevron pattern
• Nocturnal hunter that builds silken retreats
• Found in homes and known to deliver painful bites

11. Cat-faced Orbweaver

• Abdomen has pointed humps resembling cat ears
• Spin large, vertical webs on porches and eaves
• Length around 1/2 inch; harmless to humans

12. Barn Funnel Weaver

• Brown or grey with dark splotches on abdomen
• Tapered abdomen and spade-shaped cephalothorax
• Builds dense funnel webs in corners and under debris

13. Cellar Spider

• Extremely thin and spindly legs
• Gray to brown body less than 1/3 inch
• Found in cellars, garages, and other dark places

14. Triangulate Cobweb Spider

• Abdomen has bright yellow triangular pattern
• Tangles prey in messy cobwebs in corners
• Very small; 3 to 6 mm long

15. Jumping Spider

• Compact fuzzy body less than 1/4 inch long
• Variable colors and patterns
• Stalks prey by crawling close before pouncing

Spider Behavior, Habits, and Habitats in Idaho

Observing and learning about spiders can be fascinating. Here are some interesting facts about their lifestyles and where to find them:

• Male spiders court females by performing dances, offering gifts, and sending vibrations.

• Some spiders change color to blend into their surroundings for camouflage.

• Jumping spiders have excellent vision and hunt by stalking prey. They pounce up to 50 times their body length.

• Orb weavers spin fresh webs each night. Dew drops on the webs help support captured insects.

• Look for webs of the Banded Garden Spider in vegetation and shrubs. Large webs can be 2 feet wide.

• Wolf spiders carry dozens of tiny spiderlings on their abdomen after hatching.

• Cellar spiders build irregular messy webs in dark corners of basements and garages.

• The nocturnal Western Yellow Sac Spider hunts at night and rests in silken retreats during the day.

• Search under logs, stones, and debris for wolf spiders and other ground hunters.

Spider Bites & Safety Tips

Most spiders in Idaho are not aggressive and only bite when threatened or unintentionally contacted. Follow these tips to coexist safely with these fascinating creatures:

• Leave spiders that live outside alone. They help control pests.

• Avoid disturbing or handling spiders to prevent defensive bites.

• Wear gloves, long sleeves, and pants when working in spider-infested areas.

• Check shoes and clothing for hidden spiders before getting dressed. Shake out towels left on the floor before use.

• Install screens on windows and doors and seal gaps around foundations to prevent entry.

• Reduce clutter like stacks of materials that allow spiders to hide and build webs.

• Use a broom or vacuum to remove indoor webs and spiders gently without crushing them.

While the vast majority of spiders aren’t dangerous, seek medical attention for any bite that causes severe pain, swelling, or symptoms like nausea or fever. With over 650 species in the state, observing and learning about Idaho’s diverse arachnids can be an engrossing hobby. Handle them gently, appreciate their beauty and behaviors, and take care to avoid bites.