A novel actinomycete, designated strain 3H-GS17T, was isolated from the head of an ant (Lasius fuliginosus L.) and characterized using a polyphasic approach. 16S rRNA gene sequence similarity studies showed that strain 3H-GS17T belongs to the genus Actinocorallia with high sequence similarity to Actinocorallia glomerata JCM 9376T (98.13 %) and Actinocorallia longicatena JCM 9377T (97.64 %). The chemotaxonomic properties of strain 3H-GS17T were also consistent with those of members of the genus Actinocorallia. The cell wall contained meso-diaminopimelic acid and whole-cell sugars were ribose, mannose, glucose, galactose and madurose. The predominant menaquinones were MK-9(H4), MK-9(H6) and MK-9(H8). The phospholipid profile consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannoside. The major fatty acids were C16 : 0 and C18 : 1ω7с. A combination of DNA-DNA hybridization experiments and phenotypic tests were carried out between strain 3H-GS17T and its closely related strains, which further clarified their relatedness and demonstrated that 3H-GS17T could be distinguished from these strains. Therefore, strain 3H-GS17T is concluded to represent a novel species of the genus Actinocorallia, for which the name Actinocorallia lasiicapitis sp. nov. is proposed. The type strain is 3H-GS17T (=DSM 100595T=CGMCC 4.7282T).