What specific structural difference in the head scales separates the Eastern Worm Snake (C. a. amoenus) from the Midwestern Wormsnake (C. a. helenae)?

Answer

The prefrontal and internasal scales are unfused in C. a. amoenus but fused in C. a. helenae.

The primary scientific method used to distinguish between the two main subspecies of the Eastern Worm Snake, *C. a. amoenus* and *C. a. helenae*, involves a close examination of the arrangement of the scales on the front part of the head. Specifically, the identification hinges on the state of the prefrontal and internasal scales. In the typical Eastern subspecies, *C. a. amoenus*, these scales are unfused, meaning they are separated by a suture or space. Conversely, in the Midwestern Wormsnake, *C. a. helenae*, these same scales are fused together, appearing as a single plate. Additionally, size often serves as a secondary indicator, as *C. a. helenae* is generally smaller, rarely exceeding 9.8 inches compared to the nearly 11-inch standard length for *C. a. amoenus*.

What specific structural difference in the head scales separates the Eastern Worm Snake (C. a. amoenus) from the Midwestern Wormsnake (C. a. helenae)?

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