Crab Spiders in Colorado: What to Do and How to Coexist Safely

Crab spiders are fascinating creatures often found in Colorado. These arachnids are known for their crab-like appearance and unique hunting tactics. As they play a crucial role in controlling the insect population, understanding their behavior and how to handle an encounter with one can be beneficial for both people and the environment.

Many crab spiders have an impressive ability to camouflage themselves, blending seamlessly into their surroundings. This skill makes them effective ambush predators, lying in wait for unsuspecting prey to pass by. When you spot one in your Colorado garden or home, there’s no need to panic; crab spiders are not aggressive and pose no significant threat to humans.

If you come across a crab spider, it’s essential to appreciate their role in the ecosystem and practice safe handling techniques. Gently coaxing the spider onto a sheet of paper and relocating it outside can help maintain harmony between our shared spaces and these remarkable little creatures.

Crab Spiders in Colorado

Identification and Characteristics

Crab spiders belong to the family Thomisidae and are known for their crab-like appearance and sideways movements. Here are some key features to identify them:

• Eight legs with the front two pairs being longer and more robust
• Eight eyes arranged in two rows
• Body size ranging from 2 to 10 mm
• Lack of prominent web-making abilities

In Colorado, one may encounter species like the Goldenrod Crab Spider (Misumena vatia), which exhibits interesting color-changing abilities depending on its environment. Over a period of 6 to 25 days, they can change from white to yellow or vice versa to blend in with their surroundings better.

Habitat and Range

Crab spiders can be found in a variety of habitats throughout Colorado. Their range spans across gardens, fields, forests, and homes, where they act as essential biological control agents by feeding on insect pests. Here’s a quick overview of their habitat and range:

• Native to Colorado and found in drier areas below 7500 feet
• Active during the day, using their camouflage to ambush prey
• Attracted to colorful flowers, where they wait for pollinating insects

To summarize, crab spiders in Colorado are fascinating creatures with unique characteristics. They play a crucial role in maintaining the ecosystem by controlling insect populations. It’s crucial to understand their appearance, behavior, and habitat to appreciate their presence in the state.

Behavior and Diet

Hunting and Camouflage

Crab spiders, known for their hunting abilities, mainly rely on ambush tactics instead of using webs. They often use their versatile color-changing ability to blend in with their surroundings (source). For instance, the Goldenrod Crab Spider can change its color:

• From white to yellow in 10-25 days
• From yellow to white in 6 days

This camouflage allows them to hide effectively on leaves, grass, and flowers, waiting for their prey to come close before striking.

Prey and Predators

The primary diet of crab spiders consists of various insects, such as:

• Bees
• Mosquitoes
• Wasps
• Flies

As natural predators, crab spiders contribute significantly to the biological control of insect pests in gardens, fields, and homes (source). However, they also have their own set of predators, including:

• Birds
• Larger spiders
• Insect-eating mammals

In summary, crab spiders are master hunters with excellent camouflage abilities that enable them to capture their insect prey effectively. Their behavior and diet contribute to a vital ecological balance, emphasizing their importance in the ecosystem.

Color-changing abilities of the Goldenrod Crab Spider:

Reproduction and Life Cycle

Mating and Egg Laying

• Female crab spiders attract mates by producing pheromones
• Mating occurs in spring or early summer

Female crab spiders produce chemical signals called pheromones to attract males for mating. Mating usually takes place in the spring or early summer. Once they have mated, the females will create nests to lay their eggs securely. These nests often have a silken egg sac to protect and secure the eggs.

Spiderlings and Molting

• Eggs hatch into spiderlings after a few weeks
• Molting occurs as spiderlings grow and develop

After a few weeks, the eggs hatch into spiderlings. As these spiderlings grow, they undergo a process called molting. Molting involves shedding their outer skin to accommodate their growing bodies. These molts are crucial for the spiderlings to develop and transform into adult crab spiders.

Safety and Interactions with Humans

Bite Symptoms and Treatment

Crab spiders in Colorado are generally harmless to humans. Although they might bite in self-defense, their venom is not dangerous for humans. Symptoms of a crab spider bite are:

• Mild pain
• Swelling
• Redness

To treat a crab spider bite, follow these steps:

1. Clean the bite site with soap and water.
2. Apply a cold pack if there’s swelling.
3. Take over-the-counter pain relief if needed.

If you suspect an allergic reaction, consult a doctor promptly.

Comparison with Other Spiders

Crab spiders are often mistaken for other, more dangerous spiders native to Colorado. Here are a few common spiders found in the state:

• Black Widow Spider: Venomous, painful bite, females have a red hourglass pattern on their abdomen.
• Brown Recluse Spider: Venomous, necrotic bite, has a violin-shaped marking on its head.
• Daring Jumping Spider: Harmless, black with white markings and iridescent green jaws.
• Yellow Sac Spider: Non-aggressive, mildly venomous, can cause swelling and burning at the bite site.

Wolf spiders, hairy spiders, and cellar spiders (Pholcidae family) are also found in Colorado. While they might look intimidating, they are not harmful to humans:

• Wolf Spiders: Visually scary, but timid and harmless.
• Hairy Spiders: Appear menacing with their hair, but are non-aggressive.
• Cellar Spiders (Pholcidae): Long legs, prefer dark, damp spaces, and pose no threat to humans.

Keep in mind that although most spider bites are not severe, some individuals might experience an allergic reaction or infection. Always practice caution while interacting with spiders and seek medical attention if necessary.

Crab Spiders in Gardens and Homes

Beneficial vs. Pests

Crab spiders, especially those from the Family Thomisidae, are considered beneficial arthropods in gardens, as they help control insect pests by feeding on them. They blend in with plants like the Misumena vatia, waiting to capture their prey. In contrast, pests such as yellow sac spiders and wolf spiders (Lycosidae), can be invasive and destructive to plant life.

Some key features of crab spiders:

• Have front legs longer than other legs
• Do not spin webs to capture prey
• Nocturnal hunters

Examples of beneficial and pest spiders:

• Beneficial: Crab spiders (Family Thomisidae)
• Pests: Yellow sac spider, Wolf spider (Family Lycosidae)

Control and Management

While crab spiders are generally helpful in the garden, it may be necessary to control them if their population increases excessively or if they enter your home.

Habitat modification

• Remove debris and woodpiles
• Keep ground cover plants away from the foundation of your home
• Seal gaps and cracks around doors and windows

Physical removal

• Use a vacuum cleaner to remove spiders and egg sacs from corners of rooms and ceilings
• Use glue traps for capturing wandering wolf spiders and yellow sac spiders

Remember to appreciate the beneficial crab spiders in your garden, as they play their role in maintaining a balanced ecosystem by preying on pests that could harm your plants. However, if their presence becomes a concern, follow the control and management techniques mentioned above.

Resources for Identifying and Understanding Crab Spiders

Field Guides

A good field guide is essential for identifying and understanding crab spiders in Colorado. Some recommended options:

• Example Field Guide 1: This guide helps identify spiders by color, range, and other characteristics. Pros: Easy-to-use, comprehensive. Cons: Limited to a specific region.
• Example Field Guide 2: A more general guide to spiders, including web-building species. Pros: Covers a wide variety of organisms. Cons: May not have specific information about Colorado crab spiders.

Online Resources

There are various online resources available for identifying and understanding crab spiders. Here are a few:

1. Extension: Provides information on brown recluse spider identification and similar-looking spiders in Colorado.
2. Spiders in the Home: Offers general information about spiders, including their benefits in controlling insect pests.
3. Goldenrod Crab Spider: Information about this specific species, including color changes and distribution.

Remember, when identifying and dealing with crab spiders in Colorado, always stay safe and follow appropriate precautions.