December is
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
to witness.

[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.