The bean bug, Riptortus pedestris (=clavatus) Fabricius (Hemiptera: Alydidae) is a serious pest of soybean in many countries. It enters a reproductive diapause in the winter by short day length (＜13.5 h.) in Korea and Japan. The combined effects of temperatures (25℃ and 8℃) and day lengths (10L:14D and 14L:10D) upon the termination of the male"s diapause were studied. The combinations are ① HTLD = 25℃, 14L:10D treatment for 1, 2, 3 weeks and 30 days, ② HTSD = 25℃, 10L:14D treatment for 1, 2, and 3 weeks, ③ LTLD→HTLD = 8℃, 14L:10D treatment for 1, 2, and 3 weeks followed by HTLD treatment, ④ LTSD→HTLD = 8℃, 10L:14D treatment for 1, 2, and 3 weeks followed by HTLD. The amount of aggregation pheromone components secreted was adopted as the criteria for diapause termination in males. Males did not secrete aggregation pheromone under HTSD conditions. However, the males treated with HTLD for more than 21 days secreted significantly higher amounts of aggregation components, (E)-2-hexenyl (Z)-3-hexenoate and (E)-2-hexenyl (E)-2-hexenoate, compared to the control or HTSD treatments. The three components of the aggregation pheromone were secreted by the 14%, 29%, and 100% males treated with HTLD for 7 days, respectively. However more than 83% of the HTLD-treated males secreted all three components by the 30<SUP>th</SUP> day under the treatment. In comparison, the pheromone amounts secreted by the males treated with LTLD→HTLD or LTSD→HTLD were equal or less than those secreted by males with continuous HTLD treatment.

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