Embryonic development and staging of the cobweb spider Parasteatoda tepidariorum C. L. Koch, 1841 (syn.: Achaearanea tepidariorum; Araneomorphae; Theridiidae).

The cobweb spider Parasteatoda tepidariorum (C. L. Koch, 1841; syn.: Achaearanea tepidariorum) has become an important study organism in developmental biology and evolution as well as in genetics. Besides Cupiennius salei, it has become a chelicerate model organism for evo-devo studies in recent years. However, a staging system taking into account the entire development, and detailed enough to apply to modern studies, is still required. Here we describe the embryonic development of P. tepidariorum and provide a staging system which allows easy recognition of the distinct stages using simple laboratory tools. Differences between P. tepidariorum and other chelicerates, primarily C. salei, are discussed. Furthermore, cocoon production and the first postembryonic moulting procedure are described. Schematic drawings of all stages are provided to ease stage recognition.