Poor Caterpillar. Tobacco (or tomato )hornworm wasp coccoon. This wasp, also called a braconid wasp is an important parasite of the tobacco hornworm. The tiny black wasp lays its eggs in hornworms. The wasp's larval stage is a small, white legless grub that develops inside the hornworm. Once the hornworm wasp larvae fully develop they spin white oblong cocoons on the surface of the hornworm.