, the hidden leaf insects - descriptions of a new leaf insect genus and thirteen species from the former celebicum species group (Phasmatodea, Phylliidae).

While the leaf insects (Phylliidae) are a well-supported group within Phasmatodea, the genus Illiger, 1798 has repeatedly been recovered as paraphyletic. Here, the Phyllium (Phyllium) celebicum species group is reviewed and its distinctiveness from the remaining Phylliini genera and subgenera in a phylogenetic context based on morphological review and a phylogenetic analysis of three genes (nuclear gene 28S and mitochondrial genes COI and 16S) from most known and multiple undescribed species is shown. A new genus, , is erected to partially accommodate the former members of the species group. Two species, Hennemann et al., 2009 and Lit & Eusebio, 2014 morphologically and molecularly do not fall within this clade and are therefore left within Phyllium (Phyllium). The transfer of the remaining group members from Illiger, 1798 to this new genus creates the following new combinations; (Westwood, 1859), ; (de Haan, 1842), ; (Seow-Choen, 2017), ; (Yang, 1995), ; (Cumming & Le Tirant, 2020), ; (Liu, 1993), ; (Liu, 1993), ; (Liu, 1993), ; (Wood-Mason, 1875), ; (Cumming & Teemsma, 2018), ; and (Liu, 1993), The review of specimens belonging to this clade also revealed 13 undescribed species, which are described within as: from Vietnam: Quang Nam Province; from Vietnam: Quang Ngai, Thua Thien Hue, Da Nang, Gia Lai, Quang Nam, and Dak Nong Provinces; from Vietnam: Ninh Thuan Province; from China: Yunnan Province; from Indonesia: Wangi-wangi Island; from Vietnam: Quang Ngai and Lam Dong Provinces; from Vietnam: Lam Dong and Dak Lak Provinces; from Cambodia: Koh Kong and Siem Reap Provinces; from Vietnam: Lam Dong, Dak Lak, and Dak Nong Provinces; from China: Guangxi Province; from Vietnam: Ninh Thuan Province; from Vietnam: Dong Nai and Ninh Thuan Provinces; and from China: Yunnan Province. All newly described species are morphologically described, illustrated, and molecularly compared to congenerics. With the molecular results revealing cryptic taxa, it was found necessary for (Wood-Mason, 1875), to have a neotype specimen designated to allow accurate differentiation from congenerics. To conclude, male and female dichotomous keys to species for the are presented.