Chilacis

Chilacis (plural Chilacides) refers to the lateral sclerites (hardened plates) found on the underside of the abdomen in certain arthropods, particularly in some insect groups like Hemiptera (true bugs). These plates are located between the sternites (ventral abdominal plates) and the connexiva (the visible lateral edges of the abdomen formed by the tergites - dorsal abdominal plates).

The presence and form of chilacides can be a useful taxonomic character in identifying and classifying different species, particularly within Hemiptera. Their size, shape, and degree of development can vary significantly between species and even between individuals of the same species, making them a valuable feature for differentiating closely related taxa.

Functionally, chilacides provide additional protection to the soft tissues of the abdomen and may contribute to the structural integrity of the exoskeleton. They may also play a role in the flexibility and movement of the abdomen.

The term "chilacis" is derived from Greek words related to the concept of 'edge' or 'lip', referencing their position along the lateral sides of the abdominal sternites. The study of chilacides and other sclerites is an important aspect of insect morphology and aids in understanding insect evolution and systematics.