Order Polydesmida: Introduction

I specialise in the taxonomy of Polydesmida, so you might expect this section of the Tasmanian multipedes website to be complete and up-to-date. Alas, that might be true someday, but at the moment our Polydesmida are suffering from a bad case of under-description. As of October 2006, I recognise more than 120 native species, of which 64 have names. There are also two (named) introduced species.

Two full-grown native Polydesmida from northeast Tasmania: Tasmanopeltis grandis and Asphalidesmus leae (arrow).
Scale bar = 10 mm.

Before going to the Polydesmida identification page, you need to understand some basics of polydesmidan growth. These basics are described on the development page. The details are important because you need to know whether or not your specimen is an adult. Juvenile Polydesmida are very hard to identify! The development page also explains the important difference between 'H+20' and 'H+19' Polydesmida.

The diagrams above are simplified views of an adult H+20 female (top) and male (bottom). Note the red-coloured structures on the male. These are the modified legs called gonopods. In Polydesmida the gonopods are always on body segment 7, which is the third segment carrying two pairs of legs. It is the anterior pair of legs on this segment which is transformed into gonopods in adult males. The gonopods are often translucent and yellowish in colour (see image below). If your specimen does not have gonopods (if it is not a mature male), it may not be possible to identify it to species, or even to genus.

Left lateral view of mature male Lissodesmus perporosus. Some legs on right side removed for clarity.