Revision of the genus acrochordiceras hyatt, 1877 (Ammonoidea, Middle Triassic): Morphology, biometry, biostratigraphy and intra-specific variability

The family Acrochordiceratidae Arthaber, 1911 ranges in age from latest Spathian to the middle/late Anisian boundary, and it represents a major component of ammonoid faunas during that time. The middle Anisian genus Acrochordiceras Hyatt, 1877 is the most widespread taxon of the family and occurs abundantly worldwide within the low paleolatitude belt. However, there is a profusion of species names available for Acrochordiceras. This excessive diversity at the species level essentially results from the fact that sufficiently large samples were not available, thus leading to a typological approach to its taxonomy. Based on new extensive collections obtained from the Anisian (Middle Triassic) Fossil Hill Member (Star Peak Group, north-west Nevada) for which a high resolution biostratigraphic frame is available, the taxonomy and biostratigraphy of the genus Acrochordiceras Hyatt, 1877 is herein revised with respect to its intra-specific variation. Morphological and biometric studies (c. 550 bedrock-controlled specimens were measured) show that only one species occurs in each stratigraphic level. Continuous ranges of intra-specific variation of studied specimens enable us to synonymize Haydenites Diener, 1907, Silesiacrochordiceras Diener, 1916 and Epacrochordiceras Spath, 1934 with Acrochordiceras Hyatt, 1877. Three stratigraphically successive species are herein recognized in the low paleolatitude middle Anisian faunas from Nevada: A. hatschekii (Diener, 1907), A. hyatti Meek, 1877 and A. carolinae Mojsisovics, 1882. Moreover, an assessment of intra-specific variation of the adult size range does not support recognition of a dimorphic pair (Acrochordiceras and Epacrochordiceras) as previously suggested by other workers (Epacrochordiceras is the compressed and weakly ornamented end-member variant of Acrochordiceras). The successive middle Anisian species of Acrochordiceras form an anagenetic lineage characterized by increasing involution, adult size and intra-specific variation. This taxonomic revision based on new bedrock-controlled collections is thus an important prerequisite before studying the evolution of the group.

Efeito da densidade de ninfas de Aphis gossypii Glover, 1877 (Hemiptera, Aphididae) no consumo alimentar e aspectos biológicos de Orius insidiosus (Say, 1832) (Hemiptera, Anthocoridae)

Effect of ninfal density of Aphis gossypii Glover, 1877 (Hemiptera, Aphididae) on feed consumption and biological aspects of Orius insidiosus (Say, 1832) (Hemiptera, Anthocoridae). The influence of different densities of A. gossypii (10, 20, 30, 40, 50, 60 nymphs/day) on consumption rate, development time, survival, and reproduction of Orius insidiosus (Say, 1832) was investigated. The trials were carried out in climatic chamber at 25 ± 1 °C, 70±10% RH, and photoperiod 12:12h (L:D). Consumption rates of nymphs and adults increased under a linear form as the densities of aphids increased. Development time was longest when reared in 10 nymphs density (15.4 days). Nymphal survival was different under the densities of A. gossypii and no significant difference for the periods of preoviposition (4.8 days) and oviposition (8.9 days) were found. The oviposition increased with the prey densities (2.00, 11.33, 10.67, 21.30, 17.89 and 53.38 eggs), as well as the viability: 0.00, 52.49, 57.86, 58.14, 50.11 and 72.89%, respectively. Nymphs of A. gossypii as prey were suitable for the complete development of O. insidiosus.

Fecundidade e longevidade de Aphis gossypii Glover, 1877 (Hemiptera, Aphididae) em diferentes temperaturas e cultivares comerciais de crisântemo (Dendranthema grandiflora Tzvelev)

Fecundity and longevity of Aphis gossypii Glover, 1877 (Hemiptera, Aphididae) at different temperatures and commercial chrysanthemum cultivars (Dendranthema grandiflora Tzvelev). The aphid A. gossypii is one of the main pests in a number of crops both under field and protected conditions. The objective of the present study was to evaluate the fecundity and longevity of A. gossypii under different temperatures and commercial chrysanthemum cultivars (Yellow Snowdon, White Reagan and Dark Splendid Reagan) with different trichomes densities (11.3; 16.6 and 21.6 trichome/mm² of the leaf, respectively) The trials were carried out in climatic chambers, at four temperatures (15, 20, 25 and 30 ±1 °C), 70 ± 10% RH and photophase 10h. The reproductive period significantly decreased with increase of temperature in the three cultivars. In Yellow Snowdon cultivar average duration of the reproductive period was 14.3 days at 25 °C. The maximum fecundity was obtained at the temperature of 25 ºC with 3,1; 2,8 and 3,6 nymphs/female/day in the Yellow Snowdon, White Reagan and Dark S. Reagan cultivars, respectively. The total fecundity was reduced by extreme temperatures (15 and 30 °C), and was obtained at 25 °C with 35,9 nymphs/female. Females maintained in Yellow Snowdon cultivar significantly showed superiority (30,7 nymphs/female) in total fecundity in relation to White Reagan (22,1 nymphs/female) and Dark S. Reagan (22,9 nymphs/female). The Yellow Snowdon cultivar (with a lower trichome density) had a significant influence in daily and total capacity of nymphs production, showing a higher fecundity of A. gossypii females. The aphid's longevity was affected by cultivars and temperature, and this longevity decreased whit increase of temperature. The results showed that there was an interaction between the temperature and host plant on reproductive parameters of A. gossypii.