Polyzosteria yingina – Field Guide to the Insects of Tasmania

Information kindly provided by Shasta Henry:
Comprised of fifteen Australian species. Only a single species is found in Tasmania. DNA evidence shows it is endemic to the state and the populations which range from coastal to alpine habitats are genetically indistinct. They are found mostly in the central highlands, but also about 30% of the time around the east coast. Even detailed DNA analysis has shown these to be identical species so how the populations are linked is still a bit of a mystery.

They are day-active species, commonly seen around Lake Augusta, the Peter Murrell Reserve, and the Three Capes. Specimens can range from metallic bronze to matt black. Females grow slightly larger than males. The rear (10th) segment is concave in males and convex in females – to facilitate clamping and carrying of the ootheca. As all Polyzosteria are wingless, juveniles look like small adults, but reach maturity after about 1 year and can live for 4 or more years in captivity.

They are also known to host “Gordian worms” (Nematomopha: Gordioida), commonly called horsehair worms. Cockroaches parasitised by horsehair worms may be observed in mass death events on Central Highland lake shores. A relationship with water may also explain how specimens reach the coast, via downstream rafting? but observations which link the alpine and coastal populations are lacking. We wonder if they float downstream? This could be supported or complicated by the findings of Richards & Spencer (2019) -that they are also parasitised by gordian worms which leads to mass ‘strandings’ at the waters edge of the central lakes.

The name yingina (palawa kani dual name of the Great Lake) was chosen for this species in collaboration with the Tasmanian Aboriginal Center to acknowledge how such a large and noticeable species would once have had Aboriginal names.

Polyzosteria yingina
Mid March 2008
Lake Augusta, Central Highlands
Images by James Wood, used with permission.
Identification and information thanks to Shasta Henry.

Polyzosteria yingina
Late December 2010
Talinah Lagoon, Central Plateau
Feeding on Orites revoluta flowers.
Image by James Wood, used with permission. Identification thanks to Shasta Henry.

References
Henry, Shasta & Cameron, Stephen & SMOLENSKI, ADAM & Mcquillan, Peter. (2021). Polyzosteria cockroaches in Tasmania (Blattodea: Blattidae: Polyzosteriinae) represent a new, endemic species, with allopatric alpine and coastal sub-populations. Zootaxa. 4926. 384-400. 10.11646/zootaxa.4926.3.4.

Richards, Karen & Spencer, Chris. (2019). Notes on the ecology of the Tasmanian alpine cockroach Polyzosteria sp. Burmeister, 1838 (Blattodea: Polyzosteriinae) including parasitism by Gordian worms (Nematomorpha: Gordioida). 141. 27-33.