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to be sure you need to study the labral blade, the dorsal proces and the anal tubules. You can see the mandible very good and it is definitely NOT C. flavicans. To me the dorsal proces is short (in pallidus and obscuripes) and not protruded into a long pointed lobe (as in C. crystallinus and flavicans), the anal tubules seems as if they are rounded att he end (as in C. crystallinus and C. obscuripes) and not pointed (as in C. flavicans and C. pallidus). I can't really see the labral blade. If the labral blade is needle-like thin than it is C. pallidus, if it is a flattened plate then another species. In that case you have to check if the labral blade has a S-shaped edge with a long pointed end and wit honly minute smaller teeth along its edge (C. crystallinus) or is more or less rounded with many coarse teeth, especially at the end (as in C. obscuripes).