insects

Stridulation patterns and stridulatory organ were rarely investigated in the parasitoid family Mutillidae, and data still lack for any sex or species in many subfamilies. We described the morphology of stridulatory organ and the distress call of Myrmilla capitata (Myrmillinae), a small mutillid wasp in which both sexes are apterous. As in other mutillids, the stridulation is produced by rubbing a scraper on the gaster tergite II against a file on gaster tergite III and consists of sequences of pulse trains organized in two subunits (disyllabic chirps) characterized by pulses with opposite phase. Overall, sexes differed in few morphological and acoustical traits. In particular, females had wider and longer files (due to the larger tergite III), smaller ridge thickness, greater inter-ridge distance and produced sound with lower maximum frequencies. This is in accordance to the fact that individuals with wider files, and files with thicker and more separated ridges, tend to emit sounds reaching lower frequencies. Both sexes, on average, seemed to “use” about 50% of the ridges while stridulating, and the file is moved against the scraper with an average speed of about 6 mm/s. Syllable duration and pulse rate (number of pulses/s) were also affected by some morphological traits of the file. Thus, intra-specific variation in the morphology of the stridulatory organ affects stridulation features in this small velvet ant with relatively weak sexual dimorphism.

Acoustic signals are important for inter- and intraspecific interactions in many species. Their information potential depends largely on species characteristics. Here we describe quantitatively the song of Eugaster spinulosa (Johannson 1763), (Orthoptera, Tettigoniidae) and analyse the relationships of song parameters with temperature. To the best of our knowledge there are no previous descriptions available of the song of any species in the genus. Songs of seven males from the mountains of Jebilet, Marrakech (Morocco), were recorded in a semi-anechoic chamber for 105 days. Using automated thermal tables, individuals were exposed to a daily cycle of temperatures between 17.5 and 41.5°C. The calling song of Eugaster spinulosa is broader in frequency (2–28 kHz) than the song of other tettigoniids. It consists of extended series of separately audible echemes, which are polysyllabic and comprise a variable number of broadband syllables, usually between 5 and 10. The stridulatory activity of Eugaster spinulosa showed a wide thermal plasticity (ranging over 24°C between thermal thresholds). In addition to changes in temporal features, we found that an increase in temperature reduced the number of syllables per echeme.

Acoustically communicating animal species often show preferential use of specific calling sites or microhabitats from which to broadcast their calls. Site selection may be driven by different factors, including predator avoidance, reducing acoustic interference or minimising acoustic attenuation and degradation. We studied microhabitat selection in thirteen species of crickets that form the major part of an acoustically communicating ensiferan assemblage in a tropical evergreen forest in Southern India. We examined microhabitat selection in these species by comparing proportional use with availability of microhabitats. We found strong evidence for microhabitat selection by the different species. We then investigated whether the selection for microhabitats confers sound transmission benefits to these species by playing back their calls and re-recording them at different distances in both native and non native microhabitats. The calls were examined for their attenuation and degradation and compared between species and microhabitats.

We describe quantitatively the song of Eugaster spinulosa (Johannson 1763), Orthoptera, Tettigoniidae. To the best of our knowledge there are no previous descriptions available of the song of any species in the genus. The description is based on acoustic recordings of 5 males from the mountains of Jebilet, Marrakech (Morocco). Recordings were made in a semi anechoic chamber, in stereo, using G.R.A.S. 40 BE (frequency range 10 Hz – 100kHz) and Sennheiser MKH 800 P48 (frequency range 30 Hz – 50 kHz) microphones, at a sampling rate of 192 kHz, on a Sound Devices 722. The calling song consisted of sequences of a variable number of echemes, each one of which comprising 2 to 11 broadband syllables, with frequency ranging from approximately 7 kHz to almost 80 kHz, but most energy concentrated between 7 kHz and 27 kHz. We also investigated the relationship between song parameters and temperature, and attempted to identify the static and dynamic parameters of the song.

Correct identification of species and numbers of individuals is the key to biodiversity assessment. Crickets are an integral part of tropical forest ecosystems and are conspicuous due to their acoustic calling songs. Cricket calling songs are species-specific, providing reliable cues for non-invasive species identification. A cost-effective and widely used method is trained listener-based acoustic sampling. However, the effectiveness and reliability of this method has rarely been assessed in a quantitative manner. We evaluated trained listener-based acoustic sampling as a reliable and non-invasive method for rapid assessment of cricket species diversity in tropical evergreen forests. We carried out psychoacoustic experiments in the laboratory to assess the effectiveness of species identification and estimation of numbers of calling individuals by a trained listener. Further, we compared psychoacoustic sampling done in the field with the ambient noise recordings that were done simultaneously. The reliability of correct species identification by the trained listener was 100 % for 16 out of 20 species tested in the laboratory. The reliability of identifying the numbers of individuals correctly was 100% for 13 out of 20 species. The human listener performed slightly better than the instrument in detecting low frequency and broadband calls in the field, whereas the recorder detected high frequency calls with greater probability. We propose that for accurate estimation of ensiferan species richness and relative abundance in an area, trained listener-based psychoacoustic sampling is preferable for crickets and low frequency katydids, whereas broadband recorders are preferable for katydid species with high frequency calls.

I had the privilege to participate in the Austrian biological excursion to Iran between 10th and 22nd June 2007. During this excursion, we first visited lake Alagol, PA Jahan Namah (Elburz mountains) and then Golestan Province and the Golestan National Park, its facilities in Tange Gol, and the mountains around Almeh station. I tried to make contributions to the knowledge of cicadan fauna of these region with the emphasis on bioacoustic data. One of the results was the discovery of the new species Tettigetta golestani in the Golestan national park. The description has been already published*. I recorded also songs of the Cicadatra viridis, which were previously not published and hardly differ from the song of Cicadatra hyalina. Interesting is also detection and recording of the typical song of the “European” Cicadetta montana s. str. in Jahan Namah and Golestan NP. These are the farthest eastern localities proven acoustically for this species. Other species of cicadas recorded and/or collected during this field excursion will be listed in this paper.

*Gogala M., Schedl W., 2008. A new Tettigetta species from Iran and its song (Hemiptera: Cicadidae, Cicadettinae). Advances in Arachnology and Developmental Biology. Papers dedicated to Prof. Dr. Bozidar Curcic. S. E. Makarov & R. N. Dimitrijevic (Eds.). Inst. Zool., Belgrade; BAS, Sofia; Fac. Life Sci., Vienna; SASA, Belgrade & UNESCO MAB Serbia. Vienna - Belgrade - Sofia, Monographs, 12, 395-404.

Within the genus Trox the structure of the stridulation organs does not vary significantly among species. I analysed distress signals in 5 species of the genus Trox F. (T. sabulosus, T. cadaverinus, T. scaber, T. eversmannii and T. puncticollis). Each beetle was held with pincers a few seconds and then released, simulating an attempted predation by a bird. Following this disturbance, the beetle would spontaneously stridulate for several minutes. I was able to recognise various differences with regards to the length of chirps and syllables of these distress signals. These differences appear to be species specific.

Mate finding in the cicada Tettigetta josei is mediated by acoustic communication. The species-specific male song is composed by complex phrases and the shortest pulse periods vary between 4 and 8 ms, depending on the body temperature. Here we investigated if the central nervous system is able to resolve the fine time structure of the song and the temperature dependence of these responses. Intracellular recordings of auditory interneurons in the metathoracic-abdominal ganglionic complex and simultaneous auditory nerve recordings were obtained. The experimental stimuli were the species’ calling song pulses presented at different rates. Body temperature was controlled with a Peltier element. PSTH and vector strength analysis indicate that some interneurons were able to resolve pulse periods in the 3-4 ms range when the body temperature was above 24 – 26 ºC (n=6). These cells were able to resolve pulse periods of 6-8 ms even when the body temperature was at 16º C. The auditory periphery does not seem to be a limiting factor as averaging analysis in the whole nerve recordings shows that the pooled receptor response is able to resolve gaps of at least 1-2 ms in the whole temperature range tested (16-28ºC). Further studies will be necessary in order to test whether this temporal resolution is maintained at the brain level.

The oak platypodid beetle, Platypus quercivorus, produced sounds by stridulating their abdomen against the elytra. When a female was put onto the bark surface of a male-infested log, she began to walk and produced an “approaching chirp”, searching for a gallery entrance bored by a male. When finding one, she entered it, and the male pushed her back. While they pushed against each other, the female made a “pre-mating buzz” that lasted about 5-10 s. During this buzzing, the male backed out of the gallery in order to allow her in. Females that had been silenced via surgery did not evoke this male reaction; thus, males apparently identified females by their buzzing sound. The male then followed the female into the gallery, and produced an “in-gallery chirp” with his posterior abdomen visible. After a while, both sexes backed out of the hole and copulated at the entrance. Both sexes produced “stress chirps” when confined inside a cotton ball, and “spontaneous chirps” when walking alone on the surface of an oak bark piece. There are two local types in Japan and the inter-pulse-intervals in their buzzes were different.

Organization inside a colony of social insects is based on complex communication media. At present acoustic communication is found to carry various meanings (alarming, reciprocal recognition, other behavioural effects) together with chemical and tactile ones. The five species studied were Ectatomma permagnum Forel, E. quadridens Fabn, E. ruidum Roger, E. tuberculatum Oliver, Pachycondyla apicalis Latreille. The Ectatomma genus, present with 12 species in the tropical forests of Central and South America, has never been studied previously in relation to acoustic emissions. Stridulations were only heard, in the four species considered in this paper, during artificial disturbance of individuals or of the whole colony; so the role of sound production during normal life is still uncertain. Pachycondyla apicalis, while belonging to Central American forests, is also occasionally present in cocoa and coffee plantations. Ultrasonic signals were acquired using a Bruel & Kjaer 2231 phonometer with a B&K 4135 transducer (frequency response up to 100 kHz). Signals were fed into an amplifier with anti-aliasing low-pass filter to be digitally recorded and analyzed on a Pc-based Digital Signal Processing Workstation. Sampling frequencies up to 200,000 s/s allowed the recording up to 87.5 kHz. The ants were picked up with a pincer and the microphone was kept at a distance of approx. 1 cm. All the recordings made under laboratory conditions revealed the emission of pulse trains with very clear pulses extending in frequency up to 75 kHz. The sounds recorded from the genus Ectatomma appeared homogeneous in their acoustic structure, They were typically emitted in long sequences and were made by pulse-trains consisting of two subunits (disyllabic chirps) characterized by pulses with opposite phase, produced by the alternate movement of the simple plectrum against the pars stridens. In Pachycondyla sounds we found sequences of monosyllabic chirps, made by a single train of pulses. Pictures and measurements on the stridulatory apparata were made with a Scanning Electron Microscope Cambridge S 250 TP.