The Phylum Uniramia (Latin for "single branch")includes all arthropods with unbranched appendages and a single pair of antennae. Uniramians have the following characteristics in common:

Bilateral symmetry.
Through, straight gut.
Uniramous appendages, one pair of antennae and one pair of mandibles.
Two or three pairs of mouthparts consisting of mandibles and maxillae.
Externally-segmented body.
Head with lateral ocelli frequently organised into compound eyes.
Fat body in the haemocoel.
Paired gas-exchange organs, tracheae opening via lateral spiracles.
Blood lacking a respiratory function.
Internal fertilisation via spermatophores.
Larval forms often different from adult form.
Primarily terrestrial.

The Uniramians originated on land and owe their success to an efficient gas-exchange system. The excretory system is associated with the Malphigian Tube which helps reduce water loss, further assisted by a cuticular exoskeleton. The biting and chewing mouthparts enable solid food to be ingested (unlike the Chelicerates) and means that they can consume plant matter, opening up a great range of feeding niches. The mandible originated as the first pair of walking legs and in its most primitive form articulates with the body in the same way, and is armed with a cutting edge. Movement of the jaws is limited to an opening and closing movement.

FAUNA Paraguay deals with two Superclasses of Uniramians, click on the links below to access the species galleries and class introductions:

Superclass Myriapoda - Including the Centipedes (Class Chilopoda) and the Millipedes (Class Diplopoda)
The name "Myriapoda" derives from the Greek meaning "many legs".  They were likely the first major radiation of the Uniramia. The body consists of a head and a "trunk" of more or less equal segments, each bearing at least one pair of walking legs. There is only one pair of Malphigian Tubules and the head lacks median ocelli, though it does bear "Organs of Tömösvary"which are thought to be sensitive to chemicals and humidity. The antennae are segmented with each segment bearing its own muscles. Ganglia are present in each segment - the nervous system is not centralised. Myriapods are exclusively terrestrial.

Superclass Hexapoda - Including the insects (Class Insecta) or more specifically, the winged insects (Subclass Pterygota)
The name "Hexapoda" derives from the Greek meaning "six legs", a character common to all members of this superclass.
Designed by Paul Smith 2006. This website is copyrighted by law. Material contained herewith may not be used without the prior written permission of FAUNA Paraguay. Photographs on this web-site were taken by Paul Smith, Hemme Batjes, Regis Nossent, Alberto Esquivel and Hugo del Castillo and are used with their permission.