Insects.
chitin
cellulose
cellulose
chitin
Chitin is a structural carbohydrate that forms their exoskeleton
Lobsters are crustaceans, and chitin is the hard polysaccharide substance that makes up the outer shell (exoskeleton) of crustaceans. Chitin also makes up the exoskeletons of other arthropods (insects, etc.). It helps to strengthen the cell walls of fungi and the shells of mollusks as well.
Cellulose makes up the cell wall in plants.
cellulose
exoskeleton
The exoskeleton that makes up a butterfly's body is made out of chitin.
The protein that makes up the exoskeleton of arthropods like insects and crustaceans is called chitin. It provides structural support and protection to the organism, similar to how keratin provides structural support to vertebrates including humans.