- 1.
Sound output was investigated in males of two cicada species, Cyclochila australasiae Donovan and Macrotristria angularis Ståhl. These are large insects, about 4.5 cm in length, with a typical arrangement of sound-producing organs.
- 2.
Songs produced by both species consist of continuous trains of sound pulses, with a fundamental frequency close to 4 kHz. Higher harmonics fall below the 4 kHz peak by 20–30 dB. These songs are the loudest yet recorded among insects: HOdBSPL at 20cm for the protest songs of both species, and values as high as 115 dB for the vigorous calling songs of C. australasiae (mean 113 dB).
- 3.
The male tympanum (ear-drum) is between 3.3 (M. angularis) and 5.5 (C. australasiae) times greater in area than that of the female, which does not sing. The tympana and folded membranes, as well as the sound-generating tymbals, vibrate vigorously during singing; other parts of the insect do not vibrate.
- 4.
Sound output is greatest at the gap between the tympana and their protective coverings, the opercula. High values are also found close to the tymbals but not over the rest of the body. When the gap between tympana and opercula is held closed, rather than open, sound output falls by 11 dB. In the field, calling males adopt a characteristic posture, which keeps this opercular gap wide open.
- 5.
Ablating the tympana makes no difference to the sound output. But ablating the posterior half of the abdominal air sac produces a mean fall of 8.6 dB, together with a great broadening of the song's frequency content.
- 6.
The above results support the conclusion that the majority of sound is radiated through the tympanal opening in typical cicadas, with the tympana being driven passively by the resonant vibrations of air in the air sac. This system can be modelled as a Helmholtz resonator, with the tympanal opening representing the neck of the resonator.
In the field: an interview with Harald Wolf
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In our new Conversation, Harald Wolf talks about his fieldwork experiences working with desert ants in Tunisia to understand their navigation.
Propose a new Workshop
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Our Workshops bring together leading experts and early-career researchers from a range of scientific backgrounds. Applications are now open to propose Workshops for 2024, one of which will be held in a Global South country.
Julian Dow steps down and John Terblanche joins the JEB team
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After 15 years with the journal, Julian Dow from University of Glasgow, UK, is stepping down as a Monitoring Editor. We wish Julian all the best for the future and welcome John Terblanche, Stellenbosch University, South Africa, who is joining the team. Julian talks about his long association with The Company of Biologists and the journal and John tells us about his life and career in this News article.
Ecotourism affecting iguana glucose tolerance
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Ecotourists feeding grapes on skewers to north Bahamian rock iguanas may be doing the reptiles more harm than good as the sugar charged diet is giving the animals high blood sugar.
Evolution of metabolic plasticity
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In their Commentary, Frank Seebacher and Julian Beaman propose that metabolic plasticity originated in prebiotic protocells and that it was a pre-requisite for effective transfer of genetic material across generations – the hallmark of Darwinian evolution.
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