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Millipede species: native juliform millipedes (Spirostreptida)


Spirostreptida

Tasmanian Spirostreptida are very poorly known. The families Cambalidae and Iulomorphidae occur in the State, but only four species, all iulomorphids, have so far been named. The true number of Tasmanian spirostreptidans is likely to be large. At one site in the Northwest I distinguished five iulomorphids by dissecting out and examining male gonopods, and none of the five was a described species.

I recommend that students and naturalists should refer to all species in this group as 'spirostreptidan sp.' or 'Spirostreptida sp.' until we know more about the group's taxonomy in Tasmania.

I have not put a distribution map on this page because spirostreptidans are nearly ubiquitous in Tasmania. They occur in almost all habitats, although they are rare in grassland and on coastal sand dunes, and they are uncommon on farms and in gardens. In forest habitats spirostreptidans can be very abundant. In two hand-sampling studies, spirostreptidans made up 65% (Mesibov 1993b) and 48% (Mesibov 1998b) of all millipedes collected. Most species are night-wandering, and by torchlight I have watched them feeding on bracket fungi. One of our undescribed iulomorphids is Tasmania's largest millipede, growing to nearly 80 mm in length.

Iulomorphids have a particularly strong-smelling, yellow-coloured defensive secretion which stains human skin a dark purple. The secretion contains benzoquinones (Huth 2000). Other millipedes (and other arthropods) should always be preserved separately from spirostreptidans, as benzoquinones can harden alcohol-preserved specimens and stain them a dark red.

The taxonomic story so far is as follows: all named Tasmanian iulomorphids are in the genus Amastigogonus, which is based on A. tasmanianus Brölemann, 1913 from 'Tasmania'. Chamberlin (1920) described Euethogonus hardyi, also from 'Tasmania', but this species was placed in Amastigogonus by Hoffman (1972). A. fossuliger Verhoeff, 1944 was described from Lake Leake and A. nichollsi Verhoeff, 1944 from Mt Nelson. Hoffman (1972) made the latter species a synonym of A. tasmanianus. Finally, the type specimen of A. verreauxii (Gervais, 1847) was recently found in the National Museum of Natural History in Paris and redescribed (Mauriès et al. 2001); the type locality is Mt Wellington. The four named species are almost identical in general appearance. For gonopod illustrations see the cited references; note that Hoffman (1972) was the first to illustrate the gonopods of A. hardyi.

Brölemann (1913), Chamberlin (1920), Hoffman (1972), Mauriès et al. (2001), Mesibov (1993b, 1998b, 2000), Verhoeff (1944)