Mandibular shape of two invasive fire ants, Solenopsis invicta, Solenopsis geminata and a native ant Tapinoma melanocephalum were observed by light microscope and scanning electron microscopy ( SEM) . The head width and mandible size were polymorphism and widened progressively in two invasive species, while no significant difference was found in those parameters among individuals of T. melanocephalum. The T. melanocephalum has the smallest mandibles in the three types of species. It included four sharp incisor lobes, numbers of small and obtuse incisor lobes, smooth texture of ventral regions. There was no morphological difference in major, medium, minor workers of S. invicta and S. geminate mandibles. The mandibles of three sizes of workers included four sharp small teeth, with smooth texture of ventral regions. S. geminata soldier mandibles were different from workers because of blunt small teeth, relatively deep inner concave margin and rough texture of ventral regions. It was speculated that hardness mandibles of S. invicta were evolved in relation to colony founding and defending, while mandibles of S. geminata soldier were mainly related to food grinding, instead of colony defending.%应用扫描电镜和光学显微镜观察了红火蚁Solenopsis invicta Buren、热带火蚁Solenopsis geminata Fabricius和黑头酸臭蚁Tapinoma melanocephalum Fabricius的上颚类型及形态特征。头宽和上颚长度测量结果表明：两种火蚁的头宽和上颚大小具有连续性特征,黑头酸臭蚁工蚁仅1个类型,3种蚂蚁中黑头酸臭蚁的上颚最小,其前端具4个锋利切齿叶,后部有一排小而钝的臼齿叶,上颚内缘较光滑。在形态上,红火蚁的大、中、小型工蚁与热带火蚁工蚁的上颚区别不大,表面纹理光滑,都具4个锋利小齿,上颚内缘也比较光滑；热带火蚁兵蚁上颚仅3个小齿且较钝,其上颚内缘凹面比两种火蚁工蚁的深且纹理粗糙,推测红火蚁工蚁不仅用于筑巢,还用于防御,而热带火蚁兵蚁的强壮上颚可能主要用于磨碎食物,而非保卫蚁巢。
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