D. Yu. Tishechkin

New Data on Vibratory Communication in Jumping Plant Lice of the Families Aphalaridae and Triozidae (Homoptera, Psyllinea)

Vibratory signals produced by nine species of Aphalaridae and Triozidae are described and illustrated by oscillograms. Representatives of Psyllinea possess the two-way vibratory communication. A male spontaneously produces calling signals and a receptive female sings in reply to the calling male. In some species, signals produced during copulation were also recorded. On the other hand, in some cases, insects of both sexes maintained in the same cage mated actively, but produced no signals. The amplitude-temporal pattern of the male calling signals is species-specific, allowing using the acoustic characters in the taxonomy of this group.

Vibrational background noise in herbaceous plants and its impact on acoustic communication of small Auchenorrhyncha and Psyllinea (Homoptera)

Vibrations induced in plant stems by rain drops, wind, and mechanical activity of insects were studied under natural conditions. Wind and rain can induce high-frequency vibrations in the range up to 3–4 kHz and jamming insect signals completely. For this reason, small homopterans mostly emit their signals during the gaps between gusts of wind. In the regions where strong wind blows during most part of the day, they concentrate mainly in the places protected from the wind (dry river beds, hollows, and other depressions of the relief). Individuals of different species occurring on the same or neighboring plants usually sing alternately, i.e., demonstrate the same response to each other’s signals as to the wind-induced noise. Low-amplitude vibrations resulting from insect movements have no considerable impact on vibrational communication of Homoptera.

Two new species of the genus Philaenus (Homoptera, Aphrophoridae) from Iran

Two new species of Philaenus from Iran are described. Philaenus elbursianus sp. n. belongs to the Ph. signatus species group from the nominotypical subgenus. Philaenus iranicus sp. n. differs considerably from all the known representatives of the genus and was separated in a new subgenus Gyrurus subgen. n. The occurrence of this highly peculiar species in Iran may indicate that the center of origin of the genus Philaenus lies in this territory and not in the Mediterranean region as it was considered before.

The use of bioacoustic characters for distinguishing between cryptic species in insects: Potentials, restrictions, and prospects

Differences in acoustic signal patterns between closely related species often form the main precopulatory reproductive barrier in insects. For this reason, discrimination between similar forms based on their signal patterns allows one to recognize reproductively isolated species. A calling signal produced by a mature male for attracting a conspecific female is a “species ID” testifying to the fact that it belongs to the same species. This is the reason why the use of the calling signal analysis for discriminating between cryptic species or elucidating the taxonomic rank of dubious forms is highly efficient. In certain species, courtship signals also show species-specific patterns. In insect taxonomy, the study of acoustic signals is most promising in morphologically or/and ecologically heterogeneous groups. Chances that any morphologically homogeneous form will actually appear to be a complex of cryptic species are low. The degree of signal variability differs in different orders, families and even congeneric species. Therefore, in every taxon investigated for the first time, it is necessary to evaluate the limits of intraspecific variability of signals before using the acoustic characters in taxonomy. Species not involved in acoustic interactions due to allopatry, different host specialization, etc. can produce calling signals with identical patterns. Consequently, similarity in the signal structure in such species is by no means evidence of their synonymy.

Taxonomy and Biology of Leafhoppers of the Genus Macropsis (Homoptera, Cicadellidae, Macropsinae) Living on Berberis spp. (Berberidaceae)

Two Berberis-dwelling Macropsis species, M. berberidis Dub., 1966 and M. berberidicola Dub., 1966 from the West Tien Shan Mountains are redescribed. Macropsis berberidis arkytica Tishetshkin ssp. n., M. berberidis pallidicephala Tishetshkin ssp. n., and M. berberidicola narynensis Tishetshkin ssp. n. are described, the data on their host specialization, male calling signals, and distribution are provided. In spite of identical ecological preferences, the two species were never found in the same locality. Such vicariance appears to be the result of similarity of their signal pattern and competition for acoustic communication channels.

New data on the taxonomy of Middle Asian Macropsinae (Homoptera, Cicadellidae)

The taxonomic status of some forms of Macropsinae described from the Tien Shan is elucidated based on the reinvestigation of collection materials and calling signal recordings from type localities. The following synonymies are established: Macropsis ocellata Prov., 1872 = M. sattibaevi Dub., 1966, syn. n.; M. viridobrunnea Dlab., 1961 = M. persimilis Dub., 1966, syn. n.; M. vicina (Horv., 1897) = M. populicola Dub., 1966, syn. n.; Oncopsis obstructa Dlab., 1963 = O. plagiata Kuoh, 1985, syn. n. Illustrated descriptions with data on the biology and distribution are provided for all the species studied.

Pure-tone vibrational signals in small Auchenorrhyncha (Homoptera)

Investigation of vibrational calling signals of about 500 species of small Auchenorrhyncha from Russia and adjacent territories has shown that more than 10% of the species studied produce signals fully or partially consisting of pure-tone components. Among these species, there are forms dwelling on various substrates including thick tree branches, slender twigs, grass stems, petioles, and leaves. Therefore, it is impossible to associate the presence of pure-tone signals in any species with the physical properties of the inhabited substrate. Pure-tone signals were recorded both in the largest and the smallest forms. Consequently, the type of signal frequency spectrum is not related to the insect size. Experiments under natural conditions confirm the assumption that pure-tone signals are more resistant to noise than wide-band ones. This property may compensate for the disadvantage of pure-tone signals arising from stronger attenuation in certain substrates. As a result, neither pure-tone nor noise signals give unambiguous advantages for vibrational communication. Since the carrier frequency of pure-tone signals of small Auchenorrhyncha increases with temperature, it seems to be determined by the contraction frequency of tymbal muscles, rather than by the resonance properties of any cavity or cuticular structure. Regular frequency modulations occur in the signals of many species; moreover, the calling signals of some species include both pure-tone and noise components. In most of the species studied, “frequency tuning” of their signals to the physical properties of a particular substrate is impossible because of the presence of frequency modulations, temperature-related variation in the carrier frequency, or the wide host range and the absence of strong preference for any particular plant organ. Sympatric species may differ in the carrier frequency of their pure-tone signals. If the signals occupy the same frequency range they sometimes differ in their frequency modulation pattern. Consequently, conspecific signal recognition not only by amplitude, but also by frequency pattern is possible in this case, which increases the efficiency of intraspecific communication.

Acoustic signals in insects: A reproductive barrier and a taxonomic character

In singing insects, the song is an important component of the specific mate recognition system (SMRS). In communities of sympatric singing species, there is a partitioning of communication channels, the so-called “acoustic niches.” Within one community, the songs of different species always differ in temporal or frequency characters, i.e. occupy different acoustic niches. However, conspecific songs do not always act as an interspecific reproductive barrier, despite always being a SMRS component. The species that do not communicate acoustically due to allopatry, different timing of vocalization, inhabiting different biotopes, or unmatched food specializations can produce similar songs while forming reproductively isolated communities. Individuals of different sexes need not only to recognize a conspecific mate but also to evaluate its “quality.” The close-range signal (courtship song) provides more opportunities for choosing the “best” male than does the distant signal (calling song). In many species of Orthoptera, courtship includes not only acoustic but also vibrational, visual, chemical, and mechanical signals. An analysis of cricket songs showed the courtship songs to be on average more elaborate and variable than the calling songs. At the same time, due to the difference in mating behavior between the two groups, the acoustic component of courtship is used for mate quality evaluation to a greater extent in grasshoppers than in crickets. The courtship songs of grasshoppers are generally more elaborate in temporal structure than cricket songs; moreover, they may be accompanied by visual displays such as movements of various body parts. Thus, song evolution in grasshoppers is more strongly driven by sexual selection than that in crickets. According to the reinforcement hypothesis, the premating barrier between hybridizing species becomes stronger in response to reduced hybrid fitness. However, our behavioral experiments with two groups of hybridizing grasshopper species did not confirm the reinforcement hypothesis. We explain this, firstly, by a low level of genetic incompatibility between the hybridizing species and secondly, by high hybrid fitness when attracting a mate. A high competitive capability of hybrids may be accounted for by attractiveness of new elements in hybrid courtship songs. When we divide similar forms based on their songs, we in fact distinguish biological species using the criterion of their reproductive isolation. Acoustic differences between species are usually greater than morphological ones. Therefore, song analysis allows one to determine the real status of doubtful species-rank taxa, to distinguish species in a medley of sibling forms, and to reveal cryptic species in the cases when morphological studies fail to provide a univocal result. At the same time, songs are subject to intraspecific variation the range of which is different in different groups. Therefore, it is necessary to study which degree of difference corresponds to the species level before interpreting the status of some forms based on song comparisons. Besides, song similarities cannot indicate conspecificity of acoustically isolated forms; on the other hand, song differences between these forms prove that they are full-rank species.

On the taxonomy of the leafhopper genus Macropsidius (Homoptera, Cicadellidae)

Macropsidius bajanagti Dlabola, 1967 from Mongolia is downgraded to a subspecies of Macropsidius niger Matsumura, 1915; thus, its name is Macropsidius niger bajanagti Dlabola, 1967, stat. n. [erroneously given as a new synonym of M. niger in the original Russian text.—Author]. M. araxes Dlab., 1961 and M. valiturus Dlab., 1963 from the Transcaucasia are redescribed based on re-examination of the type material. The synonymy of M. demavendinus Dlab., 1974, syn. n. and M. tricostatus Logv., 1981, syn. n. under M. valiturus is established. Illustrated descriptions are given for all the species listed above. Macropsidius mitjaevi Tishetshkin, sp. n. from Middle Asia is described.