Histeridae - Anatomy

Anatomy

The Histeridae family is diverse. They rarely get over ten millimeters in length. The body form of these beetles is typically rounded or ovoid, but some are flat and rectangular. Typical coloration patterns include black, metallic green, and black with red markings.

As with all insects, the body consists of a head, thorax, and abdomen. The thorax is divided into the prothorax, mesothorax and metathorax; the dorsal side of the prothorax is a sclerotized shield, the pronotum. The Hister beetle has an exoskeleton made of chitin which gives protection to the internal organs. The elytra and forewings are normally well developed in beetles, but in Histerdiae the elytra are shortened and rectangular. The shortened elytra expose the final two of the seven tergites. Attached to the body are three pairs of jointed legs and two pairs of wings. The head has compound eyes, a mandible mouthpart, and shortened antennae. The eyes do not move; each takes a little piece of the picture to make a complete picture. The Hister's mouthpart grasps and grinds the food with two teeth. Lastly, the antennae work as sensory organs. A distinctive characteristic is that the antennae are elbowed and contain three antennomeres that form a club at the end.

Clown beetles have an open circulatory system within its hemocoel, also known as a body cavity. They have a tube shaped heart that spans the length of the body, and use hemolymph as blood. This blood does not contain any oxygen, but carries nutrients throughout the body. Spiracles are located on the abdomen and are the tracheal system of the beetle. Oxygen is brought into the body by spiracles and tiny sacks exchange the oxygen like a mammal's lung. The beetles digestive system is known as an alimentary canal. The digestive system feeds the circulatory system. Within the canal, food and water are broken down, absorbed and excreted.