They contain appendages modified for grabbing and feeding. Their excretory organ consists of a sac-like green gland . Their gas exchange is through gills. Many species contain 5 pair of walking legs. The circulatory system is open.
Barnacles are sessile crustaceans that have a modified exoskeleton in the form of a shell.
This class contains the most prolific group of animals that has ever populated the earth. The exist in almost every environment known to man. Their ability to fly and live off of plants and flowers has given them this success. They contain one pair of antennae, a pair of compound eyes, and various modified mouth parts. The thorax contains the six legs and two pair of wings.