Diplosegments

The structure of the diplosegments is normally hidden. In both living and preserved Polydesmida, the diplosegments 'telescope' into one another (image at right). This makes it difficult to see clearly just how they are built and how they are connected.
 
In fact, diplosegments, like haplosegments, are strengthened and thickened parts of the body tube (image below). However, diplosegments are much further from the simple tergite-pleurite-sternite pattern than are the haplosegments.

The image at right gives a left ventrolateral view of a midbody ring. The ring is made up of a smaller-diameter, anterior prozonite (P) and a larger-diameter, posterior metazonite (M). There is usually a constriction or waist (w) where they meet.
 
The prozonite fits into the metazonite of the next ring towards the head. The only structure of note on the prozonite is a narrow line, here called the suture (su), which may represent a join between two elements in the manufacture of a new diplosegment (before each moult). The suture is more obvious in some Polydesmida than in others (see image below, left). It is often the place where sculpturing changes on the prozonite.
 
The metazonite has the ring's ozopores (o, if present) and spiracles (sp), and the sternite (st), to which the legs attach.

Noteremus summus
(suborder Dalodesmidea), Tasmania

Orthorhachis jubata (Dalodesmidae)
Queensland, Australia

Unidentified polydesmidan
Image © 2008 by Darren5907
Used with permission