Songs and morphology in three species of the Chorthippus biguttulus group (Orthoptera, Acrididae, Gomphocerinae) in Russia and adjacent countries

Songs and morphology are compared between Chorthippus miramae (Vorontsovsky, 1928) that was previously named as C. porphyropterus and two other closely related species, C. brunneus (Thunberg, 1815) and C. maritimus Mistshenko, 1951. We compare them because the calling song of C. miramae was previously shown to have song elements similar to those of other two species. One morphological character, the length of stridulatory file, appeared to be the best character to distinguish between all three species. For C. maritimus and C. miramae, we present the morphological descriptions since they are absent in the literature. We also establish the synonymy C. maritimus = C. bornhalmi Harz, 1971, syn. n. = C. biguttulus eximius Mistshenko, 1951, syn. n. In the song analysis, we analyse not only the sound but also the leg-movement pattern, which is very helpful to find a homology between various song elements. We show that the calling song of C. miramae usually contains two elements, one element being similar to the C. brunneus calling song, and another – to the C. maritimus calling song. Despite some similarities, the calling song elements in C. miramae have some peculiarities. The courtship song of C. miramae is similar to the C. brunneus song, whereas the rivalry songs of C. miramae comprise both the maritimus-like elements and the unique ones. C. miramae generally demonstrates a richer song repertoire than the other two species.

Mikrischyrum musicum, a new katydid species from montane rainforest in southern Ecuador with complex pure-tone calling song (Orthoptera: Tettigoniidae: Pseudophyllinae: Platyphyllini)

The katydid Mikrischyrum musicum sp. nov. is described as third species of the genus, along with the remarkable low-ultrasound musical calling song of the male. It is the first species of the genus with known females, which are considerably larger than males and lack the conspicuous white spots on the pronotum. Pure-tone songs among pseudophyllines and development of pronotum markings of Platyphyllini are briefly discussed.

Neoxabea mexicana sp. nov. (Gryllidae: Oecanthinae): A new species from Mexico and a key for Neoxabea in North and Central America

A new species of tree cricket, Neoxabea mexicanasp. nov., is described from northeast Mexico. Although it has morphological similarities to two other species found in Mexico, there are distinguishing characters, such as a well-developed tubercle on the pedicel, black markings on the maxillary palpi, one of the two pairs of spots on the female wings positioned at the base of the wings, stridulatory teeth count, and the pulse rate of the male calling song. The calling song description and pre-singing stuttering frequencies are provided. Character comparisons that rule out other species in the genus are presented. The common name given to this new species is Mexican tree cricket. Sound recordings and video are available online. We also make some clarification of the status of Neoxabea formosa (Walker, 1869), described as Oecanthus formosus, and present a key of Neoxabea in North and Central America.

Lesions of abdominal connectives reveal a conserved organization of the calling song central pattern generator (CPG) network in different cricket species

Although crickets move their front wings for sound production, the abdominal ganglia house the network of the singing central pattern generator. We compared the effects of specific lesions to the connectives of the abdominal ganglion chain on calling song activity in four different species of crickets, generating very different pulse patterns in their calling songs. In all species, singing activity was abolished after the connectives between the metathoracic ganglion complex and the first abdominal ganglion A3 were severed. The song structure was lost and males generated only single sound pulses when connectives between A3 and A4 were cut. Severing connectives between A4 and A5 had no effect in the trilling species, it led to an extension of chirps in a chirping species and to a loss of the phrase structure in two Teleogryllus species. Cutting the connectives between A5 and A6 caused no or minor changes in singing activity. In spite of the species-specific pulse patterns of calling songs, our data indicate a conserved organisation of the calling song motor pattern generating network. The generation of pulses is controlled by ganglia A3 and A4 while A4 and A5 provide the timing information for the chirp and/or phrase structure of the song.

Calling and courtship songs of the rare, robust ground cricket, Allonemobius walkeri

In the original description of Allonemobius walkeri Howard & Furth, 1986, the authors describe the species’ calling songs in a table that included trill length, length of the interval between trills, pulse rate, and carrier frequency for four individuals. Further investigation of the acoustics of this species reveals that the calling songs are composed of syllables organized into echemes composed of a varying number of syllables, and organized into groups of echemes, of variable length. The echemes are separated by intervals of various lengths. The calling song is pleasing to the ear, with ~27 syllables per second and a carrier frequency of ~7.7 kHz at 25°C. The characteristics of the echemes and echeme intervals are significantly different when the cricket is singing in sunlight compared to darkness. In sunlight, echemes are shorter, but echeme intervals are longer. There is no effect on calling bout lengths. Courtship songs are quieter than calling songs, with a random delivery of soft and loud chirps in addition to fainter, rhythmic sounds randomly distributed between the chirps. Courtship songs are interspersed with long bouts of calling songs with displays lasting hours.

Pycnogaster ribesiglesiasii, a new species of Ephippigerini (Orthoptera: Tettigoniidae: Bradyporinae) from Catalonia (northeast of the Iberian Peninsula)

A new species of the genus Pycnogaster Graells, 1851 is described from Catalonia (Northeast of the Iberian Peninsula). Pycnogaster ribesiglesiasii n. sp. was collected in the Plana d’Ancosa in a calcicolous stepic scrub dominated mainly by thyme (Thymus vulgaris). L. ribesiglesiasii is compared to P. sanchezgomezi Bolívar, 1897 from which it can be separated mainly by the shape of the male cerci, the titillators and the male calling song. In addition, in the females by the protuberance of the seventh (7th) sclerite and the shape of subgenital plate.

Previous flight facilitates partner finding in female crickets

In the cricket Gryllus bimaculatus, flying occurs soon after the last imaginal molt and precedes the mating behavior in natural conditions. Here, we tested the hypothesis that flying may improve subsequent behavioral performance in a novel environment in female crickets. We developed a behavioral set-up to test female cricket responsiveness to male calling song as well as their ability to locate and find the source of the song. The male song was produced by a loudspeaker hidden behind the fabric wall of a spacious square arena. Forced flight prior to the test promoted female sexual searching behavior in the novel environment. After the flight, more females reached the hidden source zone, spent more time near the source and finally more of them climbed over the wall section immediately in front of the hidden loudspeaker. At the same time, their behavior in the arena did not differ from the control group when the calling song was not delivered, suggesting that flight exerts its behavioral effects by influencing sexual motivation. Our results support the suggestion that preceding intense locomotion facilitates sexual searching behavior of females in a novel environment.

First description of calling song of Arcyptera alzonai and possible taxonomic implications (Insecta: Orthoptera, Acrididae, Gomphocerinae)

The aim of this study was to contribute to the knowledge of Arcyptera alzonai, considered an endemic Italian species, whose biology is little known and which has an uncertain taxonomic status. Some individuals were found on a small site within its historical presence area in Susa Valley (Piedmont, NW Italy). Some recordings of the song, until today unknown, were made and analyzed. From the oscillograms obtained, no significant differences emerged with the congener species Arcyptera microptera. Also according to various authors these two species are at the moment indistinguishable from a morphological point of view. Therefore, a possible synonymy among these two taxa can be assumed which, however, must be investigated and confirmed by further research based on genetic analysis.

Modular timer networks: abdominal interneurons controlling the chirp and pulse pattern in a cricket calling song

Chirping male crickets combine a 30 Hz pulse pattern with a 3 Hz chirp pattern to drive the rhythmic opening-closing movements of the front wings for sound production. Lesion experiments suggest two coupled modular timer-networks located along the chain of abdominal ganglia, a network in A3 and A4 generating the pulse pattern, and a network organized along with ganglia A4–A6 controlling the generation of the chirp rhythm. We analyzed neurons of the timer-networks and their synaptic connections by intracellular recordings and staining. We identified neurons spiking in phase with the chirps and pulses, or that are inhibited during the chirps. Neurons share a similar “gestalt”, regarding the position of the cell body, the dendritic arborizations and the contralateral ascending axon. Activating neurons of the pulse-timer network elicits ongoing motor activity driving the generation of pulses; this activity is not structured in the chirp pattern. Activating neurons of the chirp-timer network excites pulse-timer neurons; it drives the generation of chirps and during the chirps the pulse pattern is produced. Our results support the hypothesis that two modular networks along the abdominal ganglion chain control the cricket calling song, a pattern generating network in the mesothoracic ganglion may not be required.

Internal state transition to switch behavioral strategies in cricket phonotaxis

ABSTRACTAnimals employ multiple behavioral strategies for exploring food and mating partners based on both their internal state and external environment. Here, we examined how cricket phonotaxis, which was considered an innate reactive behavior of females to approach the calling song of conspecific males, depended on these internal and external conditions. Our observation revealed that the phonotaxis process consisted of two distinctive phases: wandering and approaching. In the latter phase, crickets moved directly towards the sound source. The transition into this phase, referred to as the ‘approach phase’, was based on changes in the animal's internal state. Moreover, retention of the approach phase required recognition of the calling song, while song loss downregulated cricket mobility and induced frequent stopping. This is a typical movement in local search behaviors. Our results indicate that phonotaxis is not only a reactive response but a complicated process including multiple behavioral strategies.