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Why Spiders Suddenly Appear When You Turn on the Lights

Why Spiders Suddenly Appear When You Turn on the Lights

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Spiders. Just there, I separated people into two camps, those that love them and those that hate them. Whatever your viewpoint of them, spiders are here to stay.

These Arachnids are well adapted to our human habits and habitations (yes, that one in your bathroom that keeps on staring at you too!), but why does it seem as though they pop up out of nowhere when a light switch is flipped? Are spiders attracted to light?

Some spiders, arachnids, are attracted to lights; however, for the most part, spiders are attracted to food sources, such as moths and other flying insects. These insects are the ones who are drawn to the light, and so spiders, e.g., black widows, brown recluses, and daddy longlegs, follow suit.

Probably not the news you necessarily wanted to hear. The one option available to you would be to live in the dark (literally and figuratively) forever.

The other option would be to understand spiders a bit better; their movements, habits, and what you can do to reduce the likelihood of spiders suddenly appearing when you switch a light on!

Spiders and Light: Understanding the Connection

Spiders belong to the subclass Archanida, including scorpions, sun spiders, Daddy Longlegs, and whip-spiders/scorpions.

They are found on every continent, baring Antarctica and the Arctic regions, and they are adapted to almost every type of Biome available (except mountaintops and the ocean).

Spiders are predators, consuming a variety of prey species, from insects, fish, reptiles, and, in some cases, even birds.

The methods employed by spiders to hunt their food vary quite a bit as well.

Some spiders spin giant webs to catch prey passively; others actively fish with their webs.

Some spiders build trap door nests that they use to quickly pounce on prey as it walks past, while others use their agility, speed, and strength to overpower their quarry by running it down.

The occurrence of spiders and their prey sources is generally seasonal.

Although most spiders living in houses are protected from the cold of winter and are year-round “guests,” the overall amount of spiders found decreases during the colder winter months.

Where it lives and what it eats will also determine whether a spider is nocturnal or diurnal.

This time of the day factor is also something to consider when it comes to understanding if a spider is attracted to lights or not.

How Do Lights Influence a Spider’s Activities?

If you live in a rural area or an urban area with a park, swamp, or other natural areas close by, chances are you will have spiders coming to visit.

Insects are drawn to lights. As they leave the dark “natural” areas to get closer to the light, spiders follow.

In nature, there a relatively few light sources at night. This means that most insects would be somewhat spread out, so spiders would also be spread out.

With the use of lights, the concentration of bugs increases, which means that the frequency of finding a spider also increases.

But Why Do Spiders Pop Up When I Put a Light On?

The real issue comes in with us as people. We are visually orientated creatures. If we can see something, it makes it better (or worse!).

When we are scared or uncertain about a particular situation, we put the lights on.

The problem is; this gives the go-ahead to any bugs in the area to come flocking to the light source, and with the bugs come the spiders.

As we’ve mentioned already, spiders follow their food sources. So any spider hiding in the house knows that when the light comes on, dinner is up!

There is, however, a slight trade-off. Spiders are generally “shy” creatures who prefer to hide in secluded areas, out of sight.

This means that even though there are more spiders, they are generally trying to hide in the dark due to the increased food sources!

Ergo, when you switch on a light, you AND the spider end up getting a fright!

Diurnal vs. Nocturnal Spiders, and the Influence of Lights

The reality is; both diurnal and nocturnal spiders could be drawn to a light source.

In nature, when the lights go out, there would be a “change-over,” and the activities of each would swap.

Those that were active and hunting go into a period of rest, and vice versa.

However, with humans and artificial light sources, the natural order of things has changed.

Diurnal spiders (those who hunt or are most active during the day) would be drawn to lights because they can see better and now have more time to hunt down prey.

While nocturnal spiders (those who are more active at night) would be drawn to the light because they understand that the food is there, and they would be busy during these hours anyway.

By shifting the hours available to spiders to hunt and reproduce, we fundamentally change their behavior.

Which Spiders Are Most Likely to Come and Investigate a Light Source?

Where you live will determine, to a large extent, which spiders are most likely to find their way into your house.

But there are some common “culprits” that we can bank on arriving without a welcome.

  • American house spider (Pholcus phalangioides)
  • Black widow (Latrodectus spp)
  • Brown recluse (Loxosceles recluse)
  • Daddy longlegs (Pholcidae spp)
  • Grass spiders (Agelenopsis spp)
  • Hobo spider (Tegenaria agrestis)
  • Jumping spider (Family Salticidae)
  • Orb-weaver spiders (Family Araneoidea)
  • Sac spiders (Families Clubionidae, Miturgidae, and Corinnidae)
  • Wolf spider (Family Lycosidae)

These species are the most commonly found spiders around homes. Of the list, there are only three venomous enough to be any real threat to people.

These spiders include:

  • Black widows
  • Brown recluses
  • Sac spiders

These three sets of spiders cause the most significant concern if you happen to be bitten.

Are There Specific Lights to Which a Spider Is Drawn?

In terms of which lights draw spiders the most. There are a few factors that influence this.

  1. The brightness of the light. Brighter lights generally mean a larger illuminated area, attracting bugs, and by extension spiders, from further afield.
  1. The location of the light. Is this light exposed to the outside and, therefore, in closer contact with the insects that a spider wants to get to?
  1. In terms of color, insects, in general, are believed to be attracted more to UV, blue, green, and white lights than other colors.

Spiders, by extension, would also be more frequently found around these lights.

What Can Be Done to Reduce the Likelihood of Finding a Spider When You Switch a Light On?

Although it is impossible to eradicate spiders entirely (and in my opinion should never be tried, spiders are a benefit to the eco-system and ecology of an area), there are ways to reduce the number of spiders drawn to your house.

  1. Switch off unnecessary lights. By reducing the amount of light pollution, you attract fewer bugs; fewer bugs equals less food for spiders.
  1. Close your windows and doors when your lights are on inside. This may seem trivial, but it helps to keep insects out.
  1. Clean, sort out and pack away. By keeping a tidy house, spiders are less likely to hide in nooks and crannies around the house.

What Else Attracts Spiders, and How Can You Keep Them Away?

Although lights play a fundamental role in attracting and facilitating spiders in our homes, they are not the only reason we will find them.

As urbanization continues, we push deeper and deeper into areas where natural processes and creatures have always lived and functioned.

We are the actual home invaders.

This, however, means that we need to either come to a compromise with our housemates and learn to live together. Or employ ways to reduce the likelihood of their presence.

Some of the significant “attractants” for spiders and how to mitigate their efficacy include:

Spiders Are Attracted to Moisture

Areas of your house that are damp will attract more spiders. Spiders, like all creatures, need to drink.

Moisture build-up generally occurs in dark places, which are not frequently used/visited.

Examples include cellars/basements, attics, and the inside of roofs (especially those with geysers installed inside of them).

A way to reduce the number of spiders found in these areas is to air out these spaces as often as possible.

This will reduce the moisture build-up and cause enough activity to deter spiders from moving in.

Spiders Are Attracted to Clutter

Spiders like to hide in places where they feel safe. By having clutter in your house, you are fundamentally creating hiding places for spiders.

By reducing the amount of clutter, you also reduce the potential for spiders to live inside your house.

Another note on this point is, flies are a food source. Spiders eat flies, so you should reduce spiders by reducing the number of flies that frequent your house.

Removing garbage, compost, and other fly attractants are some ways to reduce flies, and therefore spiders.

Spiders Are Attracted to Some Colors

Apparently, spiders are repelled by the color “light blue” and are drawn to green colors.

Although it seems a tad bit drastic, if you have enough of a problem or fear of spiders, you could paint your porch or even the outside of your house a blue color.

Spiders Are Attracted to Overgrown Gardens and Overhanging Trees

Not only are spiders attracted to clutter inside your house. The outside of your home can play a role in encouraging spiders to come for a visit.

By allowing your garden to become unkempt, you create protected areas for spiders to move in and through, eventually making their way to your house.

Overhanging trees (trees that grow too close to your house, with branches that either touch your roof or walls) have a similar effect.

They provide access routes for spiders inside your garden to “move-on up” in life into the house.

Making sure your garden is well kept and trees are trimmed away from the house will reduce these issues.

Spiders Are Attracted to Shelter and Warmth

Unfortunately, this is not really something that can be reduced. You live in a house to get away from the elements, and spiders have the same idea.

The only way to mitigate this is by making sure to attend to the other factors.

Other Methods for Controlling Spider Populations

Some other control measures when it comes to spiders include:

Controlling Spiders Through Fumigation

This is a particularly drastic option, but it is generally quite effective.

Fundamentally, you are poisoning everything inside your house. This removes spiders, roaches, and most manner of other insects (and bats).

This is recommended for drastic situations.

Controlling Spiders Through the Use of Natural Repellents

There is a fair amount of anecdotal evidence out there regarding natural products that are spider deterrents.

Although probably not as effective as fumigation, it is a far-cry safer and less lethal.

Some of these include:

  • The odor of citrus fruits and cedar
  • Cinnamon
  • Peppermint oil
  • Tea tree oil
  • Eucalyptus oil
  • Vinegar
  • Garlic (vampires and spiders with one stone!)

Controlling Spiders with the Use of a Spider Catcher

Spider catchers. There are tools out there that help you catch spiders in non-lethal ways (for you and the spider).

Once caught, the spider can be safely disposed of/released.

Controlling Spiders with Cats

A lethal but not poison-related solution is a pet cat.

Cats are exceptional hunters and will even target spiders. This should reduce the frequency of their occurrence in your yard.

Controlling Spiders By Sealing Up Cracks

Consider filling them with a sealer if you have any cracks in your walls, doors, or window frames.

By leaving these open, you allow spiders an access point into your house.

Close them up before the spiders come in!

Most importantly, a clean house is a (relatively) spider-free house!

Final Thoughts

Spiders are attracted to lights, but not only by virtue of the light. They are primarily attracted to the insects the light draws.

If you live in an area with surrounding natural spaces, you are more likely to be frequented by spiders.

There are several methods to reduce the number of spiders coming to your houses, ranging from lethal to lifestyle changes.

However, the best forms of spider control are ensuring your house is clean and tidy and switching off unnecessary lights.


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