Title: High-resolution histological preparation of Araneomorphae and Mygalomorphae chelicerae using a modified petrographic technique Authors: Damien Laudier, HTL(ASCP)QIHC, Laudier Histology Abstract: Producing quality histological preparations of spider chelicerae with articulated fangs and cheliceral teeth is exceptionally challenging, if not impossible, using conventional histology techniques. Typically, these structures are examined with topographic or radiographic imaging methods, such as scanning electron microcopy (SEM) and micro computed tomography (mIcro-CT). While both are very useful tools for morphological analysis, they’re not capable of revealing the fine tissue structure and cellular details, that a histological section viewed under light microscopy can provide. This study describes a modified petrographic/hard tissue histology technique to prepare high-resolution histology sections, for qualitative and quantitative assessment of both cheliceral soft tissue and fang microstructure.