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BackgroundThe resistance of bed bugs (Cimex lectularius L.) to chemical insecticides has motivated the development of non-chemical control methods such as heat treatment. However, because bed bugs tend to hide in cracks or crevices, their behavior incidentally generates a thermally insulated microenvironment for themselves. Bed bugs located on the outer surface of luggage are less insulated and potentially more vulnerable to brief heat treatment.ResultsSoft-sided suitcases with adult male bed bugs on the outside were exposed to an air temperature of 70-75 °C. It took 6 min to kill all of the bed bugs, even those that had concealed themselves under zipper flaps or decorative piping. During heating, only one bed bug (out of 250 in total) moved into the luggage (through a closed zipper). Over long periods of time (24 h) at room temperature, adult male bed bugs on the exterior of luggage only infrequently moved inside; only 3% (5/170) had moved inside during 24 h.ConclusionsBrief exterior heat treatment of luggage is a promising way to reduce the spread of bed bugs being transported on the outer surface of luggage. This treatment will not kill bed bugs inside the luggage, but could be a component of integrated management for this pest. © 2016 Society of Chemical Industry.

The air flow pattern expected around a cylindrical object such as a tree in slow wind, is predicted from fluid mechanics to have areas of faster flow (upwind) and slower recirculating flow with eddies (downwind). An organism located on the surface of a tree would experience different flow depending on its circumferential position. If that organism was searching for a chemical signal, such as a pheromone plume, it might maximize its probability of chemodetection by placing itself in areas of greatest flow speed (the upwind surface of the cylinder, i.e., in front of the separation points). We tested whether wood cockroaches in the genus Parcoblatta exhibit such upwind positioning; they live in forests, and males actively fly from tree to tree, while searching for females releasing sex pheromone. In contrast to an expectation of upwind preference, male cockroaches were evenly distributed around trees relative to upwind (measured with a novel "feather boa" flow visualization technique), even though the wind direction was relatively steady. We investigated whether sex pheromone could be detected at any location around a cylindrical surface in a laboratory flow chamber by using Bombyx mori wing fanning as a bioassay. Although upwind moths arrayed on the surface detected pheromone more rapidly, pheromone detection occurred at least a third of the time at any position, which could explain the even distribution of Parcoblatta males around trees.

Pectinate (feathery) antennae have high resistance to air flow, and therefore most of the air approaching an antenna is diverted around it and is not available for chemical sampling by the sensory hairs on that antenna. The small fraction (approximately 10-20%) of approaching air that passes through the air spaces or gaps in the antenna decelerates and the streamlines diverge as the air approaches the antenna. Sampling a small fraction of air that is decelerating and diverging has consequences for chemoreception that are described here for the first time. The behavior of the air is predicted from application of a fluid mechanical law: the principle of continuity. As this small fraction of air decelerates and flows through the air gaps in the antenna, it will be "stretched" in the plane perpendicular to the air flow. Therefore, the air may be sampled by the sensory hairs at a greater spatial resolution than expected from the distribution of the odorant molecules in the air upstream of the antenna. However, the slowing down of odorant-laden air as it passes through an antenna will not change the perceived temporal characteristics of the chemical stimulus (e.g., the rate of odorant filament encounter). This distortion or stretching of the air sample is expected to develop within about one antennal width upstream of the antenna, as verified by examining wakes of simple physical models.