Alana Korol

April 30, 2019

A new study finds that bed bugs - like flies and insects - have favorite colors. They like dark red and black and shun dazzling white and bright yellow.

Researchers placed bed bugs in Petri dishes containing little bug-sized tents made of different colored paper. The bugs quickly crawled to the shelter, just as you would expect for insects that spend 90% of their lives hiding in cracks and crevices. But when given the chance, they gravitated toward the tents that were black and red instead of the white, yellow, or green shelters.

 

"We joked that we are all going to buy bright yellow luggage bags because the bedbugs seem not to prefer them or not to prefer laying eggs on them," said Roberto Pereira, an urban entomology research scientist at the University of Florida. Pereira was part of the team that carried out the research published Monday in the Journal of Medical Entomology.

Pereira said that one of the most common ways to get bed bugs is when you stay at a hotel with an infestation, and the insects or a few of their eggs hitch a ride home with you in your bag. Sunny-colored suitcases could help prevent that, although bed bugs might still be able to find dark folds in the fabric to stow away, he added.
  

Thick-Skinned Bed Bugs Are Beating Bug Spray

"Before you invest in a new set of luggage, there are better ways to keep bedbugs out of your home," said Dawn Gouge, an associate professor of urban entomology at the University of Arizona, who was not involved in the new research.

Gouge uses suitcases with hard exteriors and encourages "absolutely everyone to never bring luggage into their bedroom or onto a couch in the first place, and if they have an outdoor storage area (like a garage) where they can pack and unpack, that's the way to go."

Although Gouge checks her hotel rooms for signs of bed bugs -- one is reddish stains on sheets -- she noted that fewer than 1% of hotels and motels probably have them. An infestation is sometimes hard to spot.
 

 

Better Monitors?

The new study could provide some fresh insight into how to prevent bed bugs.

"The most valuable thing from this study is to say definitively if we are monitoring for these bugs, we tend to rely on black or white traps. I am convinced I should be using the black ones because the insects might avoid the lighter colors," Gouge said.

Gouge researches the best ways to monitor bed bugs in homes and other environments. However, she receives money from companies that make monitors or traps.

Two typical monitors are Climbout, which is white, and Blackout, which is (as you might expect) black. They resemble bowls with tall walls and are placed under the leg of a bed or couch. Bed bugs climb over the walls and fall into the deep bowl, where they are trapped.

Although these monitors are not enough to end a bed bug infestation—which often requires removing furniture and using pesticides—they can be handy for determining whether you have insect house guests. "The sooner you find them, the easier, the cheaper, and faster it is to get rid of the infestation," Gouge said.

 

Why Do Bed Bugs Like Dark Colors?

Pereira said these apple seed-sized insects probably instinctively prefer black and red shelters over white and yellow ones because they offer better protection from predators such as ants and spiders. Bed bugs might also gravitate to black and red shelters because they mistake the colors for fellow bed bugs and generally like to stick together for protection.

Yet another reason could be that bright colors make the insects more exposed to light, and "the more exposed these insects are, the more they lose water, and if they lose too much, they will die or have to feed again," Pereira said.

"It's hard to know what bedbugs are 'thinking,' if we can use that terminology," he said.

Pereira and his colleagues found that bed bugs, whether male or female, well-fed or hungry, preferred dark colors. The researchers let some bugs dine on live chickens, sparing humans the itchy bites, and deprived other bed bugs of their weekly blood meal.

 

Pregnant females also showed a strong penchant for laying eggs in darker tents. This behavior probably evolved millions of years ago to help protect their eggs, just like themselves, from predators, Pereira said.

In some cases, bed bugs did not display their usual aversion to light colors. For example, the littlest of bed bug babies in the first instar of development did not have any color preference when they crawled toward a paper tent. However, more mature nymphs did prefer the dark shelters.


Pereira said this behavior could be because the less mature bed bug nymphs have not developed the eyesight needed to distinguish between white, black, and the rainbow of colors.

However, Gouge suggested an alternative: These babies are transparent, not having started feasting on the blood that makes their bodies red, brown, or almost black. As a result, they can crawl onto any surface and be camouflaged, no matter what color it is.