the month when most of the really loud cicadas start to make their presence
known in eastern and northern Australia. Not surprisingly, these are also some
of the largest species. As Greengrocer populations reach the climax of their
emergence and start to fade, species like Eastern Double Drummer, Cherrynose, Redeye,
Red Roarer and Darwin Whiner are building in numbers. Another species, worthy
of mention as the December feature for ‘Cicada of the month’, is Razor Grinder.
Have you ever been in a forested area of eastern Australia where the sound of cicadas
is so loud that you can't hear yourself think? A place from which
the birds have just fled from the cacophony and the trees are festooned with big,
lumbering insects? If so, you may well have been witness to a Razor Grinder
emergence. With the call of one individual male at close quarters approaching 120db
(as loud as a jet engine), the chorus of these cicadas certainly goes beyond
the pain threshold of human hearing and at the same time is quite a spectacle
[Male Razor Grinder (Henicopsaltria eydouxii)]
Razor Grinder emerges between mid-November and January and populations persist until February–March, with stragglers occasionally remaining until April–May. It occurs from Narooma on the south coast of New South Wales north to Gladstone and also near Mackay in central Queensland. It can be an exceptionally common species from the Greater Brisbane region south to the mid-north coast of New South Wales. Populations can be found in most intact forest types, from rainforest through to dry open eucalypt forest. In some years (like in the 2013–2014 summer, for example), emergences are widespread and adult aggregations become a conspicuous feature in areas of suitable habitat, whereas, in other years, they may be quite uncommon or localised. The duration of the life cycle and the precise cues that lead to emergence remain unknown. When conditions are suitably warm, male Razor Grinder cicadas begin calling around sunrise. Males (and presumably females) are attracted to the call of conspecifics (their own species) and form localised aggregations. Initially, they call in waves through the forest, with one group commencing calling, followed by another nearby group, and another and so on. When populations are large and microclimate conditions are suitable, males will often call continuously for an extended period. They call prominently in the morning and again in the late afternoon and dusk, as well as during other parts of the day when conditions are partly cloudy.
[Aggregation of adult Razor Grinder cicadas on a eucalypt]
There is actually a different population of Razor Grinder in eastern Australia known as Laughing Razor Grinder. It occurs in association with rainforest and wet sclerophyll forest between Main Range in Queensland and the Greater Sydney region in central New South Wales. It has a rather abrupt call with strongly-defined pulses. This lies in contrast with the gradual reverberating crescendo and decrescendo of the typical Razor Grinder call. Sometimes both Razor Grinder and Laughing Razor Grinder can be found at the same location. You can listen to the calls of Razor Grinder and Laughing Razor Grinder by following the embedded links.
Some excellent preliminary research on the calling behaviour of Razor Grinder cicadas has been conducted by James Herbert-Read and colleagues in New South Wales. You can read about this research here, here and here. Their research is ongoing and will be reliant on finding suitably large populations of Razor Grinder this summer. If you encounter this species on your travels, please contact me by leaving a comment on this post, via the contact form or via Twitter so that I can pass on the sightings to the research team. Every observation helps.