Insect-detection traps baited with the synthetic aggregation pheromones of the rusty grain beetle, Cryptolestes ferrugineus (Stephens), were inserted into grain stored in primary elevator annex bins and in farm bins, or suspended in partly full or empty bins and outside under the eaves of bins. The mixture of the synthetic pheromones 4,8-dimethyl-E,E-4,8-decadienolide (ferrulactone I) and (Z)-3-dodecen-11-olide (ferrulactone II) was released from hollow polyester fibers (0.203 mm ID) positioned in the interior of the insect-detection trap. In annex bins, the number of beetles found in baited traps after 1 week ranged from 0 to 7300. In these bins, more beetles were found in traps at a depth of 30–60 cm than at 150–250 cm, and in traps with 2 fibers containing pheromone rather than with 1 fiber. In farm bins, baited and unbaited traps were relatively ineffective at grain temperatures below 14 °C. More beetles were found in baited than in unbaited traps in farm bins but the numbers were small and the differences were not significant. Few beetles were found in traps suspended in partly full or empty farm bins and none in traps suspended outside under the eaves.