January: Golden Twanger
The cicada season in most parts of Australia typically peaks by the end of the year. Cicadas appear to operate best physiologically with an ambient temperature between 20 and 30 degrees Celsius (ideally between 24 and 27°C), with some variation depending on other climatic features, such as cloud cover and wind chill factor. In cool temperate areas and especially in the subalpine zone, the window of occurrence of adult cicadas is generally quite narrow. This is most likely due to the high exposure to temperature extremes that are typically experienced in these areas. At the height of summer, it can be quite hot with maximum temperatures sometimes exceeding 40°C. However, the weather can suddenly become much colder, with minimums still often falling below 10°C. As such, this presents a challenging environment for cicadas. The cicada species that occur in these environments must have specific physical and behavioural adaptations to cope with the sudden weather changes.
There are few cicadas that occur in subalpine areas. Some notable examples include the unusual
hairy cicadas, which are distantly related to the rest of the cicadas (in a
separate family), Redeye, some hardy representatives of the genus Yoyetta, Red Scratcher and members of
the genus Diemeniana. The cicada of the month for January belongs to
the last example, and is the most widespread species in this genus: Golden
[A newly emerged male adult Golden Twanger; photograph by Melita Milner]
Golden Twanger is a small–medium sized cicada that occurs prominently
along the coasts of northern and eastern Tasmania and on the mainland from near
Tenterfield in northern New South Wales south along the ranges and coastally
south from near Wollongong, through the Australian Capital Territory into far
eastern and southern central Victoria.
It has also been found in far south-eastern South Australia. Like many cicadas, the adults are much paler immediately
after emergence and in this case exhibit attractive red colouration (pictured above). After the wings have fully developed, they attain
their true colouration (pictured below), which is mainly black above and light brown below, with
reddish-brown to olive-brown markings on the head and thorax and conspicuous
golden hairs in clusters over the abdomen.
The wings display a distinctly red costal vein and small, dark, “quotation
[A fully-coloured adult male Golden Twanger, dorsal view above, ventral view below]
The name, “Golden Twanger”, has been given to this species
because the adults exhibit a golden sheen in sunlight, which is particularly
conspicuous in the males as they move their abdomen up and down during song
production. The regular movement of the
abdomen produces the repeated “twang”-like call that is distinctive for this
species. Bryan Haywood, who discovered
the occurrence of this species in South Australia, suggested “Velvetback” as an
alternative common name for this species.
This name refers to the conspicuous covering of hairs over the thorax of
this species. Many species that occur in
cool temperate environments are similarly hairy (or tomentose), which likely
forms part of their adaptations to cold weather.
Each season, the first Golden Twanger adults appear in mainland Australia during October (later in Tasmania). Numbers typically peak in mid-summer and in some years individuals may persist until late February. Populations can be found in temperate and subalpine open grassland, swampy sedgeland, low closed and open heathland and generally in areas with low vegetation and scattered tree cover, often broadly in the vicinity of water. You can watch a video of a calling male Golden Twanger above. Further information and a distribution map for this species can be found here and you can listen to its unique and unusual calling song here.