Bees chase small hive beetles (SHB), which like to hide in dark places, into these dark crevasses. Simply place two traps at the top of the brood chamber, between the outer frames, then monitor for beetles and increase traps if you notice a heavy infestation.
Hint: For easier cleaning, spray traps out with a hose while tipping it over a garbage can.
Additional Information on Small Hive Beetles:
A relatively new type of pest for beekeepers, the small hive beetle (SHB) is originally from South Africa, and was discovered in the US in the spring of 1998. SHB are present in all areas of the United States and parts of Canada, especially a problem in the southeastern states, due to the warmer climate. Small hive beetles can easily take over a colony with little to no resistance, consuming resources of the colony, damaging the comb, and contaminating the honey.