Soil temperature and diapause maintenance in eggs of the spittlebug, Deois flavopicta (Hemiptera: Cercopidae)

Abstract

Diapausing eggs of the neotropical pasture pest, Deois flavopicta (Stal) (Hemiptera: Cercopidae), were exposed to low overnight temperatures that simulated field conditions during the dry season (23/12, 23/15 and 23/18ºC day/night), for different periods (0-60 days). After treatment, eggs were kept at 28ºC and contact water (100% humidity) until hatching. A group of diapausing eggs were kept all the time under this last condition as a control treatment. Time for hatching (in degree-days) was reduced with decrease in low overnight temperature and increase of exposure time to these cold shocks, although there was no interaction between the factors. Regression of exposure time to cold shock influencing the expected mean hatching time produced independent equations for temperatures below 18ºC and 15ºC. We constructed a model that simulates the expected proportion of the population hatching after the beginning of rainy season based on regression equations to mean hatching time and associated standard deviation. The simulation generated for the model correlated significantly with nymphal population observed in the field. These results showed that overnight soil temperatures below 18ºC, as occurs in Central and South-eastern Brazil between May and August, shorten the period of diapause, increase quiescent eggs in the soil, and may synchronize the population hatching.Key words: Insecta, phenology, dormancy, cold treatment, population dynamics. RESUMOTemperatura do solo e manutenção da diapausa em ovos da cigarrinha-das-pastagens, Deois flavopicta (Hemiptera: Cercopidae)Foram expostos ovos diapáusicos da praga de pastagens na região neotropical, Deois flavopicta (Stal) (Hemiptera: Cercopidae), a baixas temperaturas noturnas, simulando condições de campo durante a estação seca (23/12, 23/15 e 23/18ºC dia/noite), por diferentes períodos (0, 15, 30, 40, 50 e 60 dias). Após o tratamento térmico, os ovos foram mantidos a 28ºC e em água de contato (100% de umidade), até a eclosão das ninfas. Um grupo-controle de ovos diapáusicos foi mantido por todo o período experimental em altas temperaturas e umidade. O tempo para eclosão (em graus/dia) foi reduzido devido ao efeito das baixas temperaturas noturnas e ao aumento no período de exposição ao choque frio, embora não tenha sido observada interação significativa entre esses fatores. A regressão do efeito do período de choque frio no tempo médio para eclosão das ninfas provenientes de ovos diapáusicos produziu equações independentes para as temperaturas abaixo de 18ºC e 15ºC. Com base nas equações

Extraction and phytochemical investigation ofCalotropis procera: Effect of plant extracts on the activity of diverse muscles

“…Changes of the heart rate (HR) and other ECG parameters (P-R interval, R-wave amplitude, and T-wave amplitude) are expressed as mean ± standard error. The data were analyzed by paired t-test (Sujii et al, 2001).…”

Influence of pastoral systems on Mahanarva spectabilis (Distant) (Hemiptera: Cercopidae) and the entomopathogen Metarhizium anisopliae (Metsch.) Sorokin

“…In the pastoral systems with spittlebug infestation (monoculture and silvopastoral), this infestation occurred in the beginning of the rainy season (November 2013) when the total rainfall measured was 239,25 mm, providing enough soil moisture to end the quiescence process of the eggs present in the dry soil (Sujii et al, 2001); thus, rising the first M. spectabilis generation as described by Valério (2009) ). Thus, more solar radiation reaches the soil surface, which has a high correlation with spittlebug survivance (Lohmann et al, 2010).…”

Developmental Arrest during Embryonic Development of the Common Chameleon (Chamaeleo chamaeleon) in Spain

“…During the first 6-7 mo of incubation, embryos of C. chameleon in nature are in a state of developmental arrest consisting of an initial period of diapause that is followed by a period of cold torpor, a pattern parallel to that of embryos of many insects (Ando 1983;Sujii et al 2001). Oviposition by C. chamaeleon occurs from late September to early November.…”