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Bedbugs 'prefer certain colours'

1:28pm Tuesday 26th April 2016 content supplied byNHS Choices

"Bed bugs appear to have a strong preference for particular colours," BBC News reports. A new study suggests the pests prefer red and black and "hate yellow and green".

It's unclear whether changing the colour of your bed sheets would prevent an infestation of bedbugs, though certain colours could prove useful for traps.

At a glance
  • The study suggests that bedbugs have a clear preference for red and black over yellow and green.
  • The study took place under laboratory conditions, so it is unclear whether similar results would be seen in the real world.
  • The study does not prove that changing the colour of your sheets would be enough to deter bedbugs. Current guidelines for preventing an infestation still apply.

Bedbugs can be upsetting and cause a rash or itchy bumps on your skin. They don't pass on infectious diseases, but can cause an allergic reaction in some people, such as severe itching.

They can be present in even the cleanest of homes, but are more common in crowded lodgings and places with a high turnover of occupants.

Some tell-tale signs to look out for are blood spots on your sheets. Checking in the crevices of your mattress is a good way to spot them.

In this study, researchers used coloured tents in a petri dish and gave the bedbugs 10 minutes to choose their dwelling. Overall, bedbugs strongly preferred red and black, but tended to avoid colours such as green and yellow.

When they were split into sub-groups, the bedbugs' preferences varied by gender, whether they had recently been fed, and life stage.

However, this research can't tell us that yellow or green sheets would prevent an infestation of bedbugs.

If you do suspect bedbugs, it's recommended that you contact your local pest control firm, making sure they are a member of the British Pest Control Association, or your local council. 

 

Where did the story come from?

The study was carried out by researchers from Union College in Lincoln and the University of Florida.

Funding was provided by the Florida Pest Management Association and a University of Florida Endowed Professor Fund. Florida Pest Management Association is the trade group for the state's pest control companies.

The study was published in the peer-reviewed Journal of Medical Entomology on an open access basis, so you can read it for free online.

While the reporting of the study by the UK media is generally accurate, some of the coverage is not representative of the facts.

Neither the BBC's claim that bedbugs "hate yellow and green" nor the Mail Online's advice that you should "buy yellow sheets and avoid red carpets" is supported by the evidence.

The Daily Telegraph wins the shameless clickbait award of the day for managing to shoehorn in four Fifty Shades of Grey references in its first two paragraphs.

Some of the media sources carry some interesting speculation from a number of the study's authors.

One of the co-authors, Dr Corraine McNeill, explained: "We originally thought the bedbugs might prefer red because blood is red and that's what they feed on."

Dr McNeill went on to suggest that, "The main reason we think they preferred red colours is because bedbug themselves appear red, so they go to these harbourages because they want to be with other bedbugs.

"The bugs appeared to dislike yellow and green shelters, possibly because these bright colours remind them of brightly lit areas that are less safe to hide in." 

What kind of research was this?

This experimental laboratory study aimed to find out if bedbugs have a preference for living in specific-coloured dwellings.

This study is able to identify themes by observing the bedbugs' movements and examining differences by gender, life stage and nutritional status.

However, it cannot prove why they made their choices or if they would do so outside of the laboratory environment.  

What did the research involve?

The researchers set up an experiment that used small tents made from different coloured card in a petri dish to test where bedbugs would prefer to dwell.

Tests were performed to see if there were differences resulting from gender or nutritional status - starved (not fed within a week) or fed (blood one to two days before).

In a two-colour test, the bedbugs were to choose between the following eight colour dwellings against the standard white tent:

  • lilac
  • violet
  • blue
  • green
  • yellow
  • orange
  • red
  • black

A single bedbug was placed in the middle of the petri dish arena and was given 10 minutes, after which time the colour of the dwelling the bedbug was found under was recorded.

The next experiment used seven coloured tents - as above, excluding yellow - in a semi-circular arrangement and the same test was performed.

Bedbugs were tested either individually or aggregated in groups of 10 at a time. Groups were either all males, all females, or a 1:1 ratio of males and females.

Researchers also used these seven colours to test whether female bedbugs prefer to lay their eggs in dwellings of specific colours. 

What were the basic results?

Researchers found the two-choice and seven-choice colour tests indicate that red (28.5%) and black (23.4%) dwellings were the prime choices for bedbugs, while yellow and green were not popular at all. The colours chosen changed according to gender, nutritional status, aggregation and life stage.

Female bedbugs preferred lilac and violet, compared with males, who preferred red and black. When the bedbugs were fed, they appeared to be drawn to the orange and violet dwellings.

Significantly more eggs were laid in red, blue, orange and black dwellings compared with green. Bedbugs at different stages of life also appear to show different colour preferences, which may be down to the development of their eyes.  

How did the researchers interpret the results?

The researchers concluded that, "This study has given further support for bedbug preferences that may indicate that a mechanism exists for colour discrimination in bedbugs.

"Our findings should be useful in bedbug trap design as an attempt to enhance trap captures." 

Conclusion

This experimental laboratory study of bedbugs aimed to see whether the pests showed a colour preference for their dwellings.

The study found, overall, bedbugs strongly preferred red and black, but tended to avoid colours such as green and yellow.

When split into sub-groups, preferences varied by gender, whether they had recently been fed, and their life stage.

It is not clear why the researchers did not test yellow in their seven-colour test, as it would have been interesting to see whether the two-colour findings were replicated.

While these findings are of some interest and have been widely covered in the media, even the researchers say we shouldn't rush out to buy yellow sheets.

The research was only conducted over a timescale of 10 minutes, so we do not know what would have happened over time - for example, whether bedbugs would be less likely to mate and produce viable eggs if they were only given a yellow environment, or conversely whether their numbers would greatly increase in a red or black environment.

What we do know is that they need human blood to survive, prefer places that are warm, and can be carried on clothing and linen, hence why they are more common in hostels and places with a high turnover of people.

Bedbugs are very difficult to spot and can squeeze into the smallest of spaces. They are not attracted to dirt, so are not an indication of an unclean home.

Signs to look out for include:

  • an unexplained rash on the skin, or itchy bumps
  • black spots of their dried faeces on your mattress
  • mottled shells, which they may have shed
  • blood spots on your sheets where they may have been squashed
  • looking in the crevices of your mattress to see if you can spot them
  • in some cases of a large infestation, there could be a unpleasant, musty scent in rooms

If you do suspect bed bugs, it's recommended that you contact your local pest control firm, making sure they are a member of the British Pest Control Association, or your local council.

To prevent a bedbug infestation, inspect your mattress regularly for common signs and take immediate action if necessary. Avoid buying second-hand mattresses and be wary of old beds you might be using in rented accommodation.

Keeping your bedroom tidy and removing clutter, especially from the floor and under your bed, reduces the amount of hiding places for bedbugs.

Summary

"Bed bugs appear to have a strong preference for particular colours," BBC News reports. A new study suggests the pests prefer red and black and "hate yellow and green".

Links to Headlines

Bed bugs repulsed by certain colours. BBC News, April 25 2016

Bedbugs won't suck your blood - but you'll have to buy very specific sheets. Daily Mirror, April 26 2016

How to get rid of bed bugs? Buy yellow sheets and avoid red carpets: Pests have favourite colours when searching for shelter. Mail Online, April 25 2016

Why Christian Grey's 'red room' is more likely to have bed bugs. The Daily Telegraph, April 25 2016

Links to Science

McNeill CA, Pereira RM, Koehler PG, et al. Behavioral Responses of Nymph and Adult Cimex lectularius (Hemiptera: Cimicidae) to Colored Harborages. Journal of Medical Entomology. Published online April 25 2016

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