Plexus: a knot: applied to a knot-like mass of nerves, or tracheae.
In Porcellio, air-tubes (tracheae) may be present (see below).
This is the cord of tracheae communicating between one breathing-hole and another.
Tracheae opening by a pair of stigmata situated above and behind the base of the 4th or 5th or 6th pair of appendages.
A great point of interest therefore exists ...