Effects Of Acclimation, Population, And Sex On Behavioral Thermoregulation, CTMax, Symptoms Of Heat Stress, And Gene Expression of Melanoplus Differentialis, A Generalist Grasshopper - Does Temporal Thermal Heterogeneity Prepare Populations For A Warming World?

Insects thermoregulate using both canalized and plastic mechanisms. Populations of insects utilize these mechanisms to different extents, and while it is posited that the degree of thermal fluctuation a population experiences can determine the optimal combination of mechanisms to utilize, this is still being elucidated. We used three populations of the generalist grasshopper, Melanoplus differentialis (Thomas, 1856), from sites experiencing different degrees of thermal heterogeneity to test for correlations between thermal heterogeneity and 1) behavioral thermoregulation, 2) upper temperature tolerance, 3) the ability to thermally acclimate, and 4) gene expression. We found that 1) behavioral thermoregulation did not differ among sites, 2) CTMax of males, but not females, was higher at more thermally heterogeneous sites, 3) there was acclimation in some of the tested traits, but thermally heterogeneous sites did not always have the most plastic individuals, and 4) there were differences in gene expression among sites, but these differences were not between the most and least thermally heterogeneous sites. We concluded that thermal heterogeneity may play a selective role in some, but not all, of the measured thermoregulatory traits and their plasticity.

Short-horned grasshopper subfamilies feed at different rates on big bluestem and switchgrass cultivars

Grasshopper species belonging to subfamilies Melanoplinae, Gomphocerinae and Oedipodinae were tested for their feeding rate on three types of grass. All grasshopper species were offered Shawnee and Kanlow cultivars of switchgrass, Panicum virgatum L. and big bluestem, Andropogon gerardii Vitman. The grasshoppers, Melanoplus femurrubrum and Melanoplus differentialis were also tested for their feeding on turgid or wilted leaves of the Shawnee cultivar of switchgrass. We found that M. differentialis consumed more switchgrass compared to big bluestem while M. femurrubrum and Arphia xanthoptera consumed the most Shawnee switchgrass. The M. differentialis consumed more turgid grass compared to wilted switchgrass. The feeding performances show differences among grasshopper species even in the same subfamily and suggest that Melanoplinae grasshoppers may become destructive pests of switchgrass planted for biofuel production.

Contribución al conocimiento de enemigos naturales del chapulín (Orthoptera: Acridoidea) en el estado de Querétaro, México

Se realizó un inventario de enemigos naturales del chapulín (Orthoptera: Acridoidea) como resultado de observaciones hechas a través de la exploración, muestreos de ootecas, ninfas y adultosque se llevaron a cabo de 2002 a 2007 en 11,242 ha de 101 comunidades de 11 municipios del sur del Estado. Se examinaron 1620 ootecas y 8122 chapulines identificando tres especies de hongos entomopatógenos, un parasitoide y cinco depredadores. Se encontraron larvas de Epicauta spp. (Coleoptera: Meloidae) depredando ootecas de Melanoplus differentialis Thomas (Orthoptera: Acridoidea) y dos aves, Mimus polyglottos L. y Toxostoma curvirostre Swainson (Passeriformes: Mimidae) alimentándose de estadios ninfales o adultos de especies pequeñas. Se observaron estadios ninfales en la telaraña de Neoscona spp. (Araneae: Araneidae). Un depredador muy activo de ninfas pequeñas en las horas mas calientes del día fue el “moscón” Efferia spp. (Diptera: Asilidae). Se encontró a Sarcophaga spp. (Diptera: Sarcophagidae) en M. differentialis como huésped. Se observaron tres especies de hongos, Beauveria bassiana Balsamo (Hypocreales: Cordycipitaceae), Metharizium anisopliae Metschnikoff (Hypocreales: Clavicipitaceae) en todos los estadios y Entomophaga grylli Fresenius (Entomophthorales: Entomophthoraceae) en adultos de M. differentialis como hospedero, ocasionando epizootias con un buen nivel de infección.