Final answer:
The area behind the eye of the merchant grain beetle is larger than the sawtooth grain beetle.
Step-by-step explanation:
The area behind the eye of the merchant grain beetle is larger than that of the sawtooth grain beetle. This is because the merchant grain beetle has a larger and more prominent head region compared to the sawtooth grain beetle. The larger area behind the eye in the merchant grain beetle may serve various purposes such as providing more space for sensory organs or accommodating other physiological adaptations.