The given figure shows open circulatory system of cockroach with structure marked as A, B and C. Which structure is a 13 pair of wing shaped involuntary muscles and mantain blood circulation?

Alary muscles (structure marked as C) are located in pairs in the chambers of cockroach heart. They are 13 pairs of wing shaped involuntary muscles which expand and contract to facilitate the flow of haemolymph through the heart.