These March 2009 reports by Dr. Stephen Kells of the University of Minnesota and Dr. Raj Hulasare on the heat research conducted by Dr. Kells  are very interesting.

Fundamental Research on the Efficacy of Heat on Bed Bugs and Heat Transfer in Mattresses

There were three specific behavioral events that were expected during the heat up. The main expected event was escape from a lethal surface temperature. The other two main events that could be expected included a latency period before the escape event and the post-escape period. While the escape event was expected, specific behaviors during the pre- and post- escape were largely unknown. During the pre-escape period, a number of behaviors were observed including:

• Change of position – the bed bug moves its position close to the harborage. The bed bug may move on top or underneath harborage or it may move around the perimeter of the harborage.
• Movement into proximate areas. The bed bug disengages itself from the harborage and moves into neighboring regions. Often the bed bug returns to the harborage.
• Attempted feeding – Bed bugs attempt to probe the arena surface with their proboscis

In the “post escape” period, they also attempt to feed. A “looping behavior” was also observed:

sometimes the bed bug moves into a cooler part of the arena, then turns and moves back toward the harborage. Upon reaching a temperature it may reside there, it may turn back to cooler areas. Looping behavior occurred when the bug repeatedly combined advancing and retreating behavior. It is uncertain if this behavior was the result of foraging, or attempt(s) to return to the harborage.

But there are behavioral differences when temperature increases are delivered via heated air flow vs a heated surface (I’m not sure I understand this, how these delivery methods could occur in isolation):

1) Bed bugs were prone to wait in harborages when heat was delivered via air. Their threshold for escape was substantially higher.
2) Bed bugs showed a stronger propensity to stay with the harborage or would return to the harborage as air temperatures began heating the peripheral area.
3) While the distances were relatively small between the heated areas and refugia only 37.5% of bugs actually escaped.

Dr. Kells found that higher temperatures than previously reported are required to kill bed bugs when the temperature rises slowly (0.06°C/min)—possibly because of the way previous heat tests have been conducted—but it is not known what enables bed bugs to resist gradual heat stress. Also, curiously, if I’m reading this correctly, he found no differences in mortality between fed and unfed bed bugs:

Mortality did not exceed 25% for temperatures less than 45°C at all exposure times.  There was an increasing trend towards greater mortality of adult bed bugs starting at the 20-min exposure to 45°C that culminated in complete mortality at 90-min of exposure.  At 60-min exposure, approximately 50% of adult bed bugs exposed to 45°C did not survive.  Complete mortality was obtained at temperatures 48, 50, and 55°C for all exposure times except 10- min at 48°C (90%).

Here’s a table indicating minimum exposure times for complete mortality of bed bug eggs when heated at a rate of 3.6°C/h:

Story Source: University of Minnesota.