Ecological studies on Trachysphaera lobata

Trachysphaera Heller, 1858 is a genus of dwarf pill millipedes typified by a strongly ornamented and modified shape; they roll into tight balls that resemble tiny calcareous stones (Fig. 1) and it has also been suggested they resemble a small, white mass of fungi (D. Antič, pers. comm. regarding Facebook discussion). Dwarf pill millipedes are a challenge to study, their small size, and appearance like grains of sand, makes them difficult to find; in the experience of the authors often only a few specimens are found at any one time, but this may not be the situation in some caves (D. Antič, pers. comm.). Being tiny, their taxonomic features can be hard to see. Also, being pill millipedes they have telopods (instead of the gonopods found in most millipede groups) which are used to hold the females during mating rather than transfer sperm (Haacker, 1964), consisting of a chela and syncoxite. Their general morphological characters are also very variable, depending for example, upon developmental stage, amount of damage or proximity to moult (D. Antič, pers. comm.). Trachysphaera is the third most diverse genus of the order Glomerida and is distributed mainly in the Euro-Mediterranean region, the Caucasus and reaching Germany, Poland and the UK in the north (Antić et al., 2021). Specimens of Trachysphaera were first found in the UK from East Cliff, Bembridge on the Isle of Wight, in 1984 (Jones & Keay, 1986). No males were present in this first collection and as the original description of this species uses male characters to separate T. lobata from T. pyrenaica (Ribaut, 1907) this made positive species identification difficult. However, they were identified as T. lobata using somatic characters from Demange (1981) and they were examined by J.-P. Mauriès at Paris Natural History Museum.