Riptortus pedestris (Fab.) is an important pest on soybean plants in East Asia. Females lay eggs scattered not only on host plants, but also on non-host plants, probably for avoiding detection by natural enemies. Newly hatched nymphs can develop to the second instar without the need of food except water. Second instar nymphs, the first-feeding stage with a strong locomotion, need to find suitable feeding sites on host plants. The mechanism is still not well understood. Here, we found second instars were attracted by both male and female adults, but generally repelled by second and fifth instar nymphs, wherein their responses were little affected by food volatiles (soybean seeds or seedlings). Nymphs distinctly differed from adults in chemical composition of the whole-body extracts. 4-oxo-(E)-2-Hexenal was the major component in nymph’s extracts, but it was not found in adults, whereas some ester compounds, such as (E)-2-hexenyl esters, were exclusively found in adults and accounted for the main part in their extracts. The three esters, (E)-2-hexenyl (Z)-3-hexenoate (E2-6:Z3Hx), (E)-2-hexenyl (E)-2-hexenoate (E2-6:E2Hx) and myristyl isobutyrate, were male specific and had been reported as an aggregation pheromone. Synthetic 4-oxo-(E)-2-hexenal strongly repelled second instars, while (E)-2-hexenyl hexanoate emitted by both males and females attracted them. The main component of the aggregation pheromone, myristyl isobutyrate, also strongly attracted second instars. How the findings may improve the efficiency of chemical traps in fields was discussed.

Riptortus pedestris（Fab。）是东亚大豆植物上的重要害虫。雌虫不仅在寄主植物上产卵，而且在非寄主植物上产卵，这可能是为了避免被天敌发现。新孵化的若虫可以长到第二龄，除了水以外不需要食物。第二龄若虫，是具有强烈运动能力的第一采食阶段，需要在寄主植物上找到合适的觅食部位。该机制仍然不是很了解。在这里，我们发现第二龄幼虫被雄性和雌性成虫吸引，但通常被第二龄幼虫和第五龄幼虫驱除，它们的反应几乎不受食物挥发物（大豆种子或幼苗）的影响。若虫的全身提取物的化学成分与成年人明显不同。4-氧代- （É）-2-己烯醛是若虫提取物中的主要成分，但在成虫中未发现，而某些酯化合物，例如（E）-2-己烯基酯，仅在成年人中发现，并占其主要成分。提取物。（E）-2-己烯基（Z）-3-己烯酸酯（E2-6：Z3Hx），（E）-2-己烯基（E）-2-己烯酸酯（E2-6：E2Hx）和肉豆蔻酸异丁酸酯这三种酯，是男性特有的，据报道为聚集信息素。合成的4-氧-（E）-2-己二烯强烈排斥第二龄幼虫，而（E雌雄双方释放的）-2-己烯基己酸酯吸引了它们。聚集信息素的主要成分，异丁香肉豆蔻酸酯，也强烈吸引了第二龄幼虫。讨论了该发现如何提高田间化学阱的效率。