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Friday, July 25, 2014

Mike Merchant

Supplement

[Bed Bug Supplement] Born Survivors!

Bed Bug Supplement

How long can bed bugs survive without a blood meal? The answer to that question may surprise you.

June 24, 2014

Editor’s Note: The following article appeared on Mike Merchant’s blog, “Insects in the City,” which can be found at http://insectsinthecity.blogspot.com. The blog offers readers news and commentary about the urban pest management industry and is excerpted here with permission of the author.


One of the most often cited “facts” about bed bugs is that they can live more than 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 recent 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 legend says.

One of the sources of the original research suggesting extremely long lives for starved bed bugs came from a paper by a Japanese scientist named Omori in the early 1940s. This paper has been cited numerous times, principally because of republication of the data in Robert L. Usinger’s book, Monograph of Cimicidae (1966), 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°F). At more realistic indoor temperatures (65°F to 80°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°F and 69 percent relative humidity (RH). Their results for insecticide-susceptible strains are not that far from Omori’s estimates of 40 days at 81°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 three to five months without a blood meal. 

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



The author has been an entomology specialist for Texas AgriLife Extension since 1989. Readers can contact him via email at mmerchant@giemedia.com.