Which characteristic defines the lesser grain beetle?

The lesser grain beetle is primarily characterized by its dark brown coloration and its cylindrical shape, which contributes to its overall appearance and classification. This shape and color are distinct features that help in accurately identifying this beetle among other similar pests. The dark brown coloration allows it to blend in with various stored food products, which can make it a common pest in grain storage facilities.

Recognizing these physical features is crucial for pest management, as it helps in implementing effective control measures. The other characteristics offered in the options do not accurately describe the lesser grain beetle, making the identification based on its shape and color essential for those studying entomology or involved in pest control.