head is equipped with a pair of ocelli and chewing mouthparts. Each of the three thoracic segments bears a pair of true legs, and there is a pair of prolegs on the third, fourth, fifth, sixth, and last abdominal segments in all larval instars. The prothoracic segment bears one pair of spiracles, and additional pairs occur on each of the eight abdominal segments. The hemolymph (blood) of this species contains insecticyanin, a blue-colored biliprotein. When the larva feeds on its normal diet of plant foliage, it ingests pigmentacious carotenoids, which are primarily yellow in hue. The resulting combination is green. Under laboratory conditions—when fed a wheat-germ-based diet—larvae are turquoise in color due to the lack of carotenoids in their diet. The caterpillar stage of the tobacco hornworm is quite similar in appearance to that of the closely-related tomato hornworm. The larvae of these two species can however be readily distinguished by their lateral markings. Specifically, the M. sexta caterpillar has seven white diagonal lines with a black border at the first seven abdominal segments, and the horn is red or green with a red tip. The M. quinquemaculatacaterpillar has V-shaped white markings with no borders at all eight of its abdominal segments, and the horn is dark blue or black in color. During the larval stage, M. sexta caterpillars feed on plants of the family Solanaceae, principally tobacco, tomatoes and members of the genus Datura. M. sexta has five larval instars, which are separated by ecdysis (molting), but may add larval instars when nutrient conditions are poor. Near the end of this stage, the caterpillar seeks a location for pupation, burrows underground, and pupates. This searching behavior is known as "wandering". The imminence of pupation—suggested behaviorally by the wandering—can be anatomically confirmed by spotting the heart (aorta), which is a long, pulsating vessel running along the length of the caterpillar's dorsal side. The heart becomes visible through the skin just as the caterpillar is reaching the end of the final instar. A common biological control for hornworms is the parasitic braconid wasp Cotesia congregata, which lays its eggs in the bodies of the hornworms. The wasp larvae feed internally and emerge from the body to spin their cocoons. Parasitized hornworms are often seen covered with multiple white, cottony wasp cocoons, which are often mistaken for large eggs. A wasp species, Polistes erythrocephalus, feeds on hornworm larvae. Pre-pupa Before the larva