PROBLEM TO BE SOLVED: To effectively fill a gap formed in a contact portion between underfloor structures and to perform a quantitative work at a construction site, which causes a problem that occurs before completion of drying. (EN) Provided is a termite-preventing composition which can prevent termite invasion for a long period of time without being generated, and can also be applied to an existing building. An antitermite composition contains butyl rubber: 5 to 25% by mass, hydrogenated petroleum resin: 35 to 55% by mass, polybutene: 5 to 25% by mass, and inorganic filler: 15 to 35% by mass, The elongation at 20 ° C is 1000% or more. [Selection diagram] Figure 1【課題】床下構造体同士の当接部に形成される隙間部に効果的に充填できるとともに、施工現場での定量的な作業を行うことができ、乾燥が完了するまでに生じるような問題が発生することなく、長期にわたってシロアリの侵入を防止することができ、しかも既築の建築物にも適用できるような防蟻用組成物を提供する。【解決手段】防蟻用組成物は、ブチルゴム：５～２５質量％、水添石油樹脂：３５～５５質量％、ポリブテン：５～２５質量％および無機フィラー：１５～３５質量％を含有し、２０℃における伸び率が１０００％以上である。【選択図】図１
