Gastric caeca are finger-like projections of the digestive tract found in many insects. These pouches extend from the mid-gut and contain protozoa or bacteria that aid digestion, according to Ohio State University. Gastric caeca increase the surface area in the digestive tract, thus increasing digestive enzyme secretion and nutrient absorption.
Ohio State University further explains that the esophagus of the insect leads to an expanded holding area called the crop. Food moves from the crop into the proventriculus, a gizzard-like digestive structure of the foregut where the food is broken down. The gastric caeca project at the transition from foregut to mid-gut. Food passes through this transition into the ventriculus, or stomach, which is the area of most active digestion.