Ocorrência do besouro tigre Neotropical, Cylindera suturalis helvaea (W. Horn, 1903) (Coleoptera, Cicindelidae), em bancos de areia do Reservatório da Barragem da Pedra, Rio de Contas, Bahia, Brasil

The occurrence of the tiger beetle Cylindera (Plectographa) suturalis helvaea (W. Horn, 1903) in sandbanks of Reservoir Barragem da Pedra, Bahia, Brazil, is registered. Adult beetles were collected using entomological nets on sandbanks between May and September 2003. Cicindelids are one of the most conspicuous groups among invertebrates. That is why thay are well suited for bioindication of biodiversity as well as of disturbance and modification in terrestrial ecosystems.Neste estudo é registrada a ocorrência do besouro tigre Cylindera (Plectographa) suturalis helvaea (W. Horn, 1903) em bancos de areia no Reservatório da Barragem da Pedra, Bahia, Brasil. Indivíduos adultos foram coletados utilizando-se de redes entomológicas, entre os meses de Maio e Setembro de 2003. Cicindelídeos são um dos mais conspícuos grupos de invertebrados, sendo considerados como bons indicadores de biodiversidade assim como de distúrbios e modificações nos ecossistemas terrestres

Survival strategy of the bombardier beetle, Pheropsophus rivieri (Col.: Carabidae) in a Central Amazonian blackwater floodplain (Brazil)

Terrestrial invertebrates in the Central Amazonian floodplains have to cope with an annual inundation period of several months. Their life cycles are affected by this flood pulse, and most species have adopted seasonal univoltine reproductive regimes as a common survival strategy. We followed the phenology of adult bombardier beetles, Pheropsophus rivieri, at a blackwater river beach near Manaus/Brazil during 1997-1999. Gonad maturity was examined in female beetles. Adult beetles showed a pronounced seasonal activity pattern with the reproductive period confined to the first three months of falling water levels. It is concluded that P. rivieri has a seasonal, univoltine. and presumably semelparous life cycle, driven by the flood pulse. The presence of fat bodies in immature females during rising water levels indicates a delayed gonad maturation or gonad dormancy. The species exhibits a migratory survival strategy, typical for most carabid species from Central Amazonian floodplains, although it remained unsolved where adults pass the period of rising water levels. A possible parasitic relation of larval P. rivieri with mole crickets is discusse

Exceptional anoxia resistance in larval tiger beetle, Phaeoxantha klugii (Coleoptera : Cicindelidae)

The tiger beetle Phaeoxantha klugii inhabits Central Amazonian floodplains, where it survives the annual inundation period in the third-instar larval stage submerged in the soil at approximately 29 degreesC for up to 3.5 months. Because flooded soils quickly become anoxic, these larvae should be highly resistant to anoxia. The survival of adult and larval P. klugii was therefore tested during exposure to a pure nitrogen atmosphere in the laboratory at 29 degreesC. Adult beetles were not resistant (< 6 h). Survival of larvae decreased over time, maximum survival was 15 days, whereas time to 50% mortality was 5.7 days (95% confidence interval 3.8-7.9). Anoxia resistance was additionally tested in third-instar larvae submerged within sediment for 40 days before anoxia exposure in the laboratory. Anoxia resistance was greatly enhanced in these larvae, showing a survival rate of 50% after 26 days of anoxia exposure. It appears that the gradual flooding process and/or the submersion phase induced a physiological alteration, most probably a strong depression in metabolic rate, which requires some days for induction. The degree of anoxia resistance in larval P. klugii is remarkable among terrestrial arthropods worldwide, even more so considering the high ambient temperatures. The species is well-suited to serve as a model organism for studying the physiological mechanisms of anoxia and submersion resistance in terrestrial arthropods inhabiting tropical floodplains

Spatio-temporal distribution of larval and adult tiger beetles (Coleoptera : Cicindelidae) from open areas in Central Amazonian floodplains (Brazil)

We investigated the regional occurrence and guild structure of tiger beetle species from open areas in Central Amazonian floodplains. Populations of larvae and adult beetles were observed during monthly field excursions from 1997-1999 to reveal life cycles, habitats, diet activity patterns, and other behavioral traits. One of the eight species found in open areas of Central Amazonia is represented by two subspecies. All except one species were found to reproduce in either white- or blackwater floodplains (6 and 4 species/subspecies, respectively). Habitats of larvae and adult beetles, diet activity patterns, as well as life cycles are given for all species. As a result of different life cycles (seasonal temporal segregation), diel activity patterns (diet temporal segregation), (micro-)habitats (spatial segregation), and behavior, intraspecific segregation of larvae and adult beetles was common. Its extent varied between species, ranging from almost complete segregation to partial overlap. Interspecific segregation was extensive. In larvae this was mainly due to different (micro-)habitat preferences (spatial separation). In adult beetles it was related to different life cycles, activity patterns and (micro-)habitats (seasonal, diet temporal, and spatial segregation). In addition, mandible gapes of adult beetles were different in species within guilds. Larvae of solely one or two pairs of species and adult beetles of only two pairs were found to live steadily together. Hence, guild structures showed strong niche separation. Possible implications for a better understanding of coexistence of tropical tiger beetles as well as for mechanisms mediating coexistence in general are discusse