<p>For most insects, decision-making by female parents during egg-laying site selection is key to the survival and development of their offspring. In many insect species, females refer to the behaviour of conspecifics when choosing oviposition sites. Investigating how information from the behaviour of others (or their traces) influences egg-laying decision-making is essential for understanding the biology of insects and developing innovative pest management measures. We focussed on the oviposition behaviour of the red-necked longhorn beetle <i>Aromia bungii</i> (Coleoptera:&#xa0;Cerambycidae), a severe invasive pest damaging stone fruit trees in Europe and Japan. We showed that <i>A. bungii</i> selects sites previously oviposited on by conspecifics. In laboratory bioassays, the females preferred to add their eggs onto treated branches with conspecific eggs and tended to lay more eggs on branches that already had larger numbers of conspecific eggs. This study is the first to demonstrate the attraction to conspecific cues during egg-laying decision-making in longhorn beetles, while females in these taxa generally avoid traces of the same sex. Our results imply that the benefits of joining conspecifics and engaging in high larval density, such as suppressing the host resistance, outweigh the costs of experiencing resource competition in this species. We provide novel insights into the reproductive behaviour of longhorn beetles, which could be useful for designing environmentally friendly control strategies such as an ‘egg trap’ to encourage the pests to deposit eggs on removable substrates.</p>