Thursday, June 2, 2011

The life span of bed bugs

One of the most often cited "facts" about bed bugs is that they can live over a year without a blood meal. But is it true?  That's what Andrea Polanco and colleagues at Virginia Tech set out to investigate in their recently published article in the open-access journal insects (open access means articles are free and open to the public).  Their work, as well as a careful reading of the original source of the one-year-survival statistic, suggests that bed bugs (at least starved bed bugs) may not be as long-lived as the legend says.

One of the sources of the original research suggesting extremely long lives for starved bed bugs came from a paper by Japanese scientist named Omori in the early 1940s.  This paper has been cited numerous times, principally because of republication of the data in Usinger's (1966) book on bed bugs, which has been a basic reference for researchers since the bed bug resurgence. If you check the original data from Omori carefully, you will see that adult bed bugs live longest (15 months) at low temperatures (50 degrees F). At more realistic indoor temperatures (65 to 80 degrees F--Omori didn't look at in-between temperatures) the average survivorship of unfed adults was about 160 to 40 days, respectively. Other, less carefully conducted research prior to 1950 suggests maximum bed bug lifespans of 5 to 19 months.

Polanco's work was conducted at a constant 78 degrees F and 69% RH.  Their results for insecticide susceptible strains are not that far from Omori's estimates of 40 days at 81 degrees F.  But the most interesting conclusion of Polanco's work is that insecticide resistant strains of bed bugs (which are increasingly common worldwide) live for a significantly shorter time when starved (39 to 76 days) than their insecticide-susceptible counterparts (73 to 106 days).  The longest life span observed in Polanco's research was an insecticide-susceptible 5th instar nymph, which lived 143 days without a blood meal. Field strains of resistant bed bugs did not live longer than 80 days. These data are still a far cry from the 12 to 15 month longevity figure often cited to amaze people about bed bug resiliency.

One of the most interesting things about Polanco's team's work is the demonstration that insecticide-resistance can make an organism less fit in some ways.  This has been seen in other insects (e.g., cotton bollworm in cotton) when insecticide pressure is removed and insect populations revert (through natural selection) back to susceptible forms--presumably because the susceptible forms are overall more fit for survival.

So when talking to your customers about bed bugs, it's time to drop the 12 month statistic.  It's more realistic to say that today's bed bugs can live 3 to 5 months without a blood meal. 

Don't get me wrong.  Two to four months without food is still impressive.  But bed bugs are not immortal, and like all pests they too have their limits of endurance.

9 comments:

James said...

Other current bed bug researchers have seen similarly shorter life spans. I think Andrea and Dini are the only ones that have tried to quantify it.

Sidrah said...

That’s good to know, that they do not live longer. They wreak enough havoc in their limited life span. I am much relieved to know about the research mentioned in your article. Thanks for sharing it.

Anonymous said...

Thank you for this article. I live in D.C. and currently going through this maddness. Everyone was telling me, including the pest control company, I would be living with them for at least a year. It is good to know that some research was done showing the average life span is less than 6 month. I have am taking all the precautions and I am now happy know that by the end of the year, they will no longer be part of my life.

Anonymous said...

"Madness" is correct....I've gone though it with my daughter in CA and here back home. We have been bite free for 8 months. I am still waiting for bites. Unfortunately of all the research I've done(and it's been a lot), this is the only article that Ive seen that gives this short life span.

Anonymous said...

Nightmare is right. My daughter's ex-boyfriend bought a used quilt at a yard sale and then.... It is now over a year later and my daughter was truly losing her mind, although the infestation appears to be mild. Then she mentioned a bedbug tent (made of fine mesh, designed for travelers but useful at home), which I bought for her. Since then she has not had another bite; she is now growing calmer and less paranoid. We are hoping that in another 6 months the monsters will have been beaten. Your article has given us hope, since we thought that she'd have to continue this battle for 18 months!

Anonymous said...

People should know about the bedbug tent (made of fine mesh and available from Amazon) we bought. Although the infestation we are fighting in my daughter's condo is mild, it was making her crazy; but now, with the tent, she is able to sleep in peace and is becoming calmer. We are most grateful for your article because it has given us hope that we may get to the end of this nightmare in 6 months rather than 18!

Mike Merchant, PhD said...

I don't have experience with the tents or bags or pjs to protect sleepers. My impression is that some of these might be uncomfortable,but if not, they seem like another way to get a restful night's sleep. It is important to stay in one's bedroom during the eradication to reduce the risk of bed bugs spreading to other parts of the home or apartment, so if these devices help I'm all for them.

Anonymous said...

The thesis in this blog is flawed, based on the presented evidence. The study at VT maintained a constant 78F temperature, which based on the data being presented is a temperature range in which beg bugs are much less able to thrive. Notice that in previous studies that bed bugs in the ~65F range lived significantly longer. Thus, the bed bugs studied at VT may have lived much longer had it been conducted at a lower temperature. 78F is the temperature at a nursing home, not a typical single family dwelling.

Mike Merchant, PhD said...

If you read the article, the authors compared survival times of resistant and susceptible strains at the same temperature. Resistant field strains (those collected recently from the "wild", with high levels of insecticide resistance) consistently lived longer without food (40-50% longer) than insecticide susceptible strains. Unfortunately, it is difficult to obtain "wild" susceptible strains for comparison, and strains in the lab may be genetically different. However, the survival rates do appear to be lower for resistant bed bugs, when temperature is controlled.