Ants do have hearts. This organ serves the same function as in humans, but its structure and relationship to the rest of the circulatory system is very different. In ants, blood flows throughout the body cavity rather than in branching arteries and veins.
The heart of an ant is a long tube that runs along its back. Although the insect's blood, called hemolymph, is free-floating, the heart itself is kept in place by numerous fibers and muscles. The heart pumps in waves that direct hemolymph forward toward the head. The part of the tube directly near the head is called the aorta. In humans, the aorta travels extensively throughout the body before branching off into many smaller vessels, but an ant's aorta ends once it reaches the head.