The sternum (pl. "sterna") is the ventral portion of a segment of an arthropod thorax or abdomen. In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... Subphyla and Classes Subphylum Trilobitomorpha Trilobita - trilobites (extinct) Subphylum Chelicerata Arachnida - spiders,scorpions, etc. ... Diagram of a tsetse fly, showing the head, thorax and abdomen The thorax is a division of an animals body that lies between the head and the abdomen. ... The abdomen is a part of the body. ...

In insects, the sterna are usually single, large sclerites, and external. However, they can sometimes be divided in two or more, in which case the subunits are called sternites, and may also be modified on the terminal abdominal segments so as to form part of the functional genitalia, in which case they are frequently reduced in size and development, and may become internalized and/or membranous. Orders See taxonomy Insects are invertebrates that are taxonomically referred to as the class Insecta. ... Sclerites are hardened body parts. ... A sex organ, or primary sexual characteristic, narrowly defined, is any of those parts of the body (which are not always bodily organs according to the strict definition) which are involved in sexual reproduction and constitute the reproductive system in an complex organism; namely: Male: penis (notably the glans penis...

The term is also used in other arthropod groups such as crustaceans, arachnids and myriapods. Classes Remipedia Cephalocarida Branchiopoda Ostracoda Maxillopoda Malacostraca The crustaceans (Crustacea) are a large group of arthropods (55,000 species), usually treated as a subphylum. ... Orders Acarina Amblypygi Araneae Opiliones Palpigradi Pseudoscorpionida Ricinulei Schizomida Scorpiones Solifugae Uropygi The arachnids, Arachnida, are a class of invertebrate animals in the subphylum Chelicerata. ...

Sternites on the pleon (abdomen) of a crustacean may be referred to as pleonsternites. These are the sites of attachment of the pleopods (swimming legs). Antennules Pereiopods Carapace Pleopods Uropods Telson The body of a decapod crustacean is made up of nineteen body segments grouped into two main body parts, the cephalothorax and the abdomen. ... Antennules Pereiopods Carapace Pleopods Uropods Telson The body of a decapod crustacean is made up of nineteen body segments grouped into two main body parts, the cephalothorax and the abdomen. ...