Polydesmidae, Leach, 1815

Shear, William A., 2012, Snoqualmia, a new polydesmid milliped genus from the northwestern United States, with a description of two new species (Diplopoda, Polydesmida, Polydesmidae), Insecta Mundi 2012 (238), pp. 1-13 : 2

Polydesmidae and Macrosternodesmidae

Polydesmidae and Macrosternodesmidae in North America are far from distinct, even though the two families are traditionally referred to separate superfamilies (extensive discussion in Shear and Shelley 2007). At this point in time, indigenous North American polydesmids are to be found east of the Central Plains, in the Mississippi Valley and Appalachian Mountains, and in the Pacific Northwest. Macrosternodesmids sensu strictu (that is, excluding nearctodesmids) are rare in the Appalachians and Mississippi Valley (but see Lewis 2002) and seem almost to exclude polydesmids in the Southwest and California.

For the time being, I regard as members of Polydesmidae any species in which the efferent duct of the gonopod debouches through a pulvillus, a pad or region of the gonopod which is set with fine cuticular projections (not setae), and whose telopodites possess a distinct distal zone (sensu Shear and Shelley 2007). In addition, most of these species have a loop or at least a curve in the course of the efferent duct just before the pulvillus, and may also have a reservoir distal to the loop. A distinct endomerite may or may not be present. An endomerite is here considered to be a separate branch of the gonopod originating from the basal region of the prefemur on the anteromedial side.

Using developmental studies, Petit (1976) in a little-cited paper, established that the postcoxal part of the polydesmid gonopod develops entirely from the prefemur. Therefore, using the term tibiotarsus for the part of the gonopod extending beyond the pulvillus is misleading. Here I substitute the term distal zone as suggested by Shear and Shelley (2007). Similarly it can no longer be considered accurate to call the region traversed by the efferent duct the femorite because the femur of the walking leg does not form part of the gonopod.