Blue vane traps are scientific instruments used to survey and monitor specific insect populations, particularly wild bees. Physically, they consist of a cylindrical body with prominent vertical fins, or “vanes,” that intersect at the top with a collection cup below. These traps are not for general pest control but are used by researchers and citizen scientists to gather data on pollinator health and diversity.
How Blue Vane Traps Work
The effectiveness of a blue vane trap hinges on exploiting the sensory biology of its target insects. Many bee species have photoreceptors highly sensitive to the blue-to-violet portion of the light spectrum. The specific shade of blue on the traps acts as a powerful visual attractant, luring bees from a distance as they forage.
Once a bee is drawn in by the color, the trap’s physical structure facilitates its capture. The intersecting vanes act as baffles, interrupting the bee’s flight path. As an insect collides with a vane, it is funneled downward into the collection chamber below, which is designed to prevent escape.
Target Insects and Bycatch
These traps are primarily designed to capture various species of wild bees. Studies show they are effective at sampling a high diversity of native bees, including bumble bees, carpenter bees, and sweat bees. Research indicates that blue vane traps are particularly good at capturing larger-bodied bees compared to other trap types, like pan traps.
While selective, the traps will capture non-target insects, a phenomenon known as bycatch. Common bycatch includes flies, beetles, and some species of wasps that are also attracted to the blue color. A frequent concern is the capture of honey bees; however, the specific blue hue is less attractive to them than to many native bee species, making the traps specialized for wild bee surveys.
Proper Use and Placement
For the trap to function effectively, it must be placed correctly in the environment. The ideal height is around chest level, or 1 to 1.5 meters from the ground, mounted on a shepherd’s hook or a dedicated pole. It should be positioned in a sunny area near flowering plants to maximize its visibility to foraging bees, but not so close that it is hidden by dense foliage.
The collection cup must be filled with a liquid to retain the captured insects. For short-term surveys lasting 24-48 hours, the standard fluid is water mixed with a few drops of unscented dish soap. The soap breaks the surface tension of the water, causing any insect that falls in to sink. For longer-term scientific studies, a preservative like propylene glycol is used to keep specimens from decomposing.
Regular maintenance is necessary for accurate data collection. Traps using soapy water should be checked and emptied every one to three days to prevent specimens from decaying. When collecting, the contents are poured through a fine mesh strainer or a coffee filter to separate the insects from the liquid. These specimens are then transferred to a container with a preservative like ethanol for later analysis.