Review of Biogeography, Host Range and Evolution of Acoustic Hunting in Ormiini (Insecta, Diptera, Tachinidae), Parasitoids of Night-calling Bushcrickets and Crickets (Insecta, Orthoptera, Ensifera)

Interest in parasitoids has grown with the recognition that host-parasitoid systems offer opportunities to examine fundamental questions in behavioural and evolutionary ecology. Tachinid flies of the Ormiini possess a conspicuously inflated prosternal region, enabling them to detect the mating songs of their hosts. This speciality makes them a highly suitable group for studies of adaptive radiation. To emphasise further research in this important group of parasitoids, their biogeography and host species are summarised.The Ormiini are a particularly small group, containing only 68 described species of predominantly tropical, especially neotropical forms. A table of host-parasitoid relations reveals that predominant parasitism is of bushcrickets. The exploitation of cricket songs appears to be a derived pattern that evolved as a host switch some time after the Eocene.Hypotheses concerning fly-host coevolution and the reasons for the development of hearing are discussed, and include the question of mate finding and avoidance of bats as predators.     

Insect duets: underlying mechanisms and their evolution

Abstract. Duetting between the sexes in insects involves the use of airborne acoustic signals, substrate vibration and bioluminescence. Unlike avian duets, in which females may initiate the interaction, among insects the duet starts with the male, and the female usually provides a brief reply. Insect duets are characterized by low variance in the reply latency of the female (the time between a key element in the male call and the onset of the female's response). Duetting is reviewed principally in Orthoptera but also in Plecoptera, Hemiptera, Neuroptera and bioluminescence in the Coleoptera. The mechanisms of the duet are examined first, followed by evolution and the associated change in searching strategies of each sex. As defined, the duet has distinct temporal characteristics and these are compared with acoustic interactions among males in those species that exhibit male–male synchrony and alternation. For insects, the key element of a duet for species' recognition is low variance in the reply latency of females. In cases in which the male's initiating signal is extremely short, reply latencies become indicators of species' recognition. However, in those species in which the initiating male call is under selection through female choice, the male call is predictably longer and occasionally more complex. Under these circumstances, reply latencies often increase, creating an opportunity for alternative male tactics. When alternative tactics exist in nature, males may decrease the intensity of their call, insert a trigger pulse that signals to the female the end of its complex call, or males may even add a masking signal that obscures the competing signal.     

Cicada acoustic communication: potential sound partitioning in a multispecies community from Mexico (Hemiptera: Cicadomorpha: Cicadidae)

Multispecies cicada communities in neotropical rainforests produce a complex and intense acoustic environment. In a fragment of a Mexican rainforest (Veracruz, Mexico), a cicada community at the end of the dry season consisted of nine species ( Daza montezuma; Pacarina schumanni; Miranha imbellis; Dorisiana sutori; Fidicinoides picea; Fidicinoides pronoe; Quesada gigas; one species of the genus Neocicada and one uncaught canopy species). Seven of the nine species formed dense choruses at dawn and at dusk. Each species showed preferences in the height of calling sites. Males of the species were solitary or gregarious, and followed a 'call-fly' or a 'call-stay' calling strategy. Acoustic signals of each species had particular time and frequency patterns. All these specific features appear to separate the nine species acoustically and lead to a partitioning of the acoustic environment. The acoustic partitioning might decrease the risk of heterospecific courting and mating.© 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 75 , 379–394.     

Echolocation of Multiple Targets in 3-D Space from a Single Emission

Using frequency-modulated echolocation sound, bat can capture a moving target in real three-dimensional (3-D) space. It is impossible to locate multiple targets in 3-D space by using only the delay time between an emission and the resultingechoes received at two points (i.e., two ears). To locate multiple targets in 3-D space requires directional information for each target. The spectrum of the echoes from nearly equidistant targets includes spectral components of both the interference between the echoes and the interference resulting from the physical process of reception at the external ear. The frequency of the spectral notch, which is the frequency corresponding to the minimum of the external ear's transfer function (EEDNF), provides a crucial cue for directional localization. In the model we present, a computational model todiscriminate multiple close targets in 3-D space utilizing echoes evoked by a single emission by distinguishing the interference of echoes from each object and the EEDNF corresponding to each target.     

Performance of hairy root cultures of Cichorium intybus L. In bioreactors of different configurations

Summary A transformed root culture of Cichorium intybus L. cv. Lucknow Local grown in different configurations of bioreactors was examined. The roots grown in an acoustic mist bioreactor showed the best performance in terms of increased specific growth rate (0.072d⁻¹) and esculin content (18.5gl⁻¹), the latter of which was comparable to that of shake flask data. C. intybus hairy root cultures grown in an acoustic mist bioreactor produced nearly twice as much esculin as compared to roots grown in bubble column and nutrient sprinkle bioreactors. Studies relating to on-line estimation of conductivity and osmolarity to predict the growth of hairy root cultures are also discussed. The results demonstrate the efficacy and the advantages of an acoustic mist bioreactor for the cultivation of hairy root cultures, especially with reference to C. intybus hairy roots.     

Climatic stress, food availability and human activity as determinants of endemism patterns in the Mediterranean region: the case of dung beetles (Coleoptera, Scarabaeoidea) in the Iberian Peninsula

Abstract. A study to assess the influence of abiotic (climatic conditions) and biotic factors (food resources, habitat preference and human activity) on endemism patterns of dung beetles in the Mediterranean region was conducted in the Iberian Peninsula and the Balearic Islands. The Thermicity Index (It), the Mediterraneity Index (Im3) and the Aridity Index (Ia) were used to assess the influence of abiotic factors. Relative rabbit density (DR), the proportion of landscape used historically for grazing by sheep and goats and the nature of the food resource were used to assess the influence of biotic factors. Relative endemism (EN) of dung beetle assemblages was positively and significantly related with all of the factors considered. However, the Aridity and Mediterraneity Indices are the best predictors of EN. The predicted endemism (EN = 0.017 Ia + 0.004 Im3 + 0.422) was highly positively and significantly related with the observed endemism. Dung beetle assemblages with the highest relative endemism were observed in the south-eastern part of the Iberian Peninsula. This distribution corresponded to the highest Aridity and Mediterraneity. In contrast, dung beetle assemblages with lower endemism were located in more humid and temperate areas. Assemblages of dung beetles with the highest endemism comprise many species adapted to aridity and the exploitation of dry dung pellets. Conservation of traditional grazing activity by pellet-dropping sheep and goats might benefit the maintenance of dung beetle biodiversity in Mediterranean ecosystems.