Showing papers in "Neotropical Entomology in 2015"
TL;DR: A better understanding of the mechanisms that determine the variability in the sensitivity of insects would accelerate the worldwide release of commercial RNAi-based approaches.
Abstract: The time has passed for us to wonder whether RNA interference (RNAi) effectively controls pest insects or protects beneficial insects from diseases. The RNAi era in insect science began with studies of gene function and genetics that paved the way for the development of novel and highly specific approaches for the management of pest insects and, more recently, for the treatment and prevention of diseases in beneficial insects. The slight differences in components of RNAi pathways are sufficient to provide a high degree of variation in responsiveness among insects. The current framework to assess the negative effects of genetically modified (GM) plants on human health is adequate for RNAi-based GM plants. Because of the mode of action of RNAi and the lack of genomic data for most exposed non-target organisms, it becomes difficult to determine the environmental risks posed by RNAi-based technologies and the benefits provided for the protection of crops. A better understanding of the mechanisms that determine the variability in the sensitivity of insects would accelerate the worldwide release of commercial RNAi-based approaches.
106 citations
TL;DR: It was showed that increasing plant diversity within crops by associating cultivated species can reduce aphid infestations, since host plants are more difficult to locate.
Abstract: Increasing plant diversity within crops can be beneficial for pest control. In this field study, the effects of two wheat and pea associations (mixed cropping and strip cropping) on aphid populations were compared with pure stands of both crops by observations on tillers and plants. Pea was more susceptible to infestations than wheat. As expected, the density of aphid colonies was significantly higher in pure stands during the main occurrence periods, compared with associations. Additionally, flying beneficials, such as not only aphidophagous adult ladybirds but also parasitoid, hoverfly and lacewing species that feed on aphids at the larval stage, were monitored using yellow pan traps. At specific times of the sampling season, ladybirds and hoverflies were significantly more abundant in the pure stand of pea and wheat, respectively, compared with associations. Few parasitoids and lacewings were trapped. This study showed that increasing plant diversity within crops by associating cultivated species can reduce aphid infestations, since host plants are more difficult to locate. However, additional methods are needed to attract more efficiently adult beneficials into wheat and pea associations.
30 citations
TL;DR: It is concluded that the benefits of silicon to sugarcane quality and Sugarcane resistance to stalk borers are dependent on theugarcane variety.
Abstract: Sugarcane is grown extensively throughout the world including more than 100,000 ha in Khuzestan province, Iran. The pink stalk borers Sesamia are key pests of sugarcane in this region, while other stalk borers will occur in sugarcane worldwide. Application of silicon as a soil amendment has provided plant mitigation to both biotic and abiotic stresses. Silicon has been shown to enhance resistance of sugarcane against stalk borers. Field trials were conducted to determine the effects of calcium silicate against infestations of stalk borers Sesamia spp. and on yield quality. Experiments were conducted with three sugarcane varieties CP69-1062, IRC99-01, and SP70-1143 and two rates of calcium silicate (400 and 800 kg/ha). Percentage of stalk damaged, percentage of bored internodes, length of borer tunnel (mm), number of larvae + pupae per 100 stalks, number of exit holes, and cane yield quality were determined. We demonstrate significant reduction on borer population and damage under silicon treatment, but greater reduction in the percentages of stalk damage, bored internodes, moth exit holes, and length of borer tunnel and number of larvae and pupae per 100 stalks were observed in the susceptible variety CP69-1062. Silicon treatment positively affected cane and sugarcane juice quality of for the variety CP69-1062, but not for SP70-1143. We conclude that the benefits of silicon to sugarcane quality and sugarcane resistance to stalk borers are dependent on the sugarcane variety.
29 citations
TL;DR: The data suggests that the variation in houseFly resistance among seasons could be due to fitness costs or to the cessation of selection pressure in the off-season, which has significant implications for the use of insecticides in house fly management.
Abstract: The house fly, Musca domestica L. (Diptera: Muscidae), is a pest of livestock and has the ability to develop resistance to different insecticides. We assessed the fluctuations in seasonal stability of house fly resistance to insecticides from poultry facility populations in Pakistan. House fly populations were collected from poultry facilities located at Khanewal, Punjab, Pakistan in three seasons (July, November, and March) to investigate the fluctuations in their resistance to conventional (organophosphate, pyrethroid) and novel chemistry (spinosyn, oxadiazine, neonicotinoid) insecticides. Laboratory bioassays were performed using the feeding method of mixing insecticide concentrations with 20% sugar solutions, and cotton pads dipped in insecticide solutions were provided to tested adult flies. Bioassay results showed that all house fly populations had varying degrees of susceptibility to tested insecticides. Comparisons between populations at different seasons showed a significant fluctuation in susceptibility to organophosphate, pyrethroid, spinosyn, oxadiazine, and neonicotinoid insecticides. Highest resistant levels were found for organophosphate when compared with other tested insecticides. The resistance to conventional insecticides decreased significantly in March compared with July and November, while resistance to oxadiazine and avermectins decreased significantly in November. However, resistance to spinosad and imidacloprid remained stable throughout the seasons. All conventional and novel chemistry insecticides were significantly correlated with each other in all tested seasons except nitenpyram/lambda-cyhalothrin and nitenpyram/imidacloprid. Our data suggests that the variation in house fly resistance among seasons could be due to fitness costs or to the cessation of selection pressure in the off-season. These results have significant implications for the use of insecticides in house fly management.
27 citations
TL;DR: The data clearly indicated that fitness cost of methoxyfenozide and its sublethal effects on S. litura has an important impact on its population dynamics.
Abstract: In the present study, two experiments were designed to investigate the lethal and sublethal effects of methoxyfenozide on Spodoptera litura (F.). The first experiment was conducted to explore the fitness cost of methoxyfenozide resistance in a methoxyfenozide-resistant strain (selected with methoxyfenozide for 13 consecutive generations), leading to resistance ratio to methoxyfenozide 83.0- and 2359-fold higher when compared to the field and susceptible populations with a fitness cost of 0.17. In the second experiment, second instars of the susceptible strain were treated with sublethal doses of methoxyfenozide (LC30, LC20, and LC10) by diet incorporation for larval feeding for 3 days. It was observed that higher concentrations of methoxyfenozide significantly prolonged the larval and pupal development time of S. litura as compared to the control treatment. The number of eggs per female, egg hatching, sex ratio, and longevity of adults of methoxyfenozide-treated groups was greatly reduced as compared to untreated S. litura. Our data clearly indicated that fitness cost of methoxyfenozide and its sublethal effects on S. litura has an important impact on its population dynamics.
24 citations
TL;DR: Given differences in flight activity at different taxonomic levels, it is strongly recommended to monitor by light trapping throughout the night to effectively sample saturniid and sphingid assemblages, even though the activity of Sphingidae sharply declines after midnight.
Abstract: Variations in diel activity among hyperdiverse tropical communities of moths, despite representing a key component of niche partitioning between species, have barely been studied so far. Using light trapping from dawn to sunset over a 1-year period in French Guiana, we investigated these variations within and between two families of moths (Sphingidae and Saturniidae). Our results revealed contrasting patterns in flight activity at night between Sphingidae and Saturniidae. Sphingidae reached their peak in species richness and abundance between 7:00 and 8:00 p.m., followed by a decrease around 11:00 p.m. to midnight, whereas Saturniidae were continuously present throughout the night, with a peak around midnight. In addition, we found changes in diel activity among some of the most common genera in each family, highlighting distinct behavioral, physiological, and functional traits among taxa. Given differences in flight activity at different taxonomic levels, it is strongly recommended to monitor by light trapping throughout the night to effectively sample saturniid and sphingid assemblages, even though the activity of Sphingidae sharply declines after midnight. These results improve the general natural history information of tropical moths and reinforce the need of further research on the ecological and taxonomic consequences of differences in diel activity.
22 citations
TL;DR: Both A. millefolium essential oil and thujone exhibited a repellent activity against this insect at the higher doses tested, demonstrating their potential as repellents for this species.
Abstract: Aegorhinus nodipennis (Hope) (Coleoptera: Curculionidae) is an important native pest in fruit crops that is mainly found in European hazelnut fields in the south of Chile. We investigated the behavioral response of A. nodipennis to volatile compounds released from the essential oil of Achillea millefolium and its main constituent using olfactometric bioassays. Gas chromatographic and mass spectral analysis of the A. millefolium essential oil revealed the presence of 11 compounds. Monoterpene β-thujone (96.2%) was the main component of the oil. Other compounds identified were α-thujone, 1,8-cineole, p-cymene, and 4-terpineol, all with percentages below 1%. Both A. millefolium essential oil and thujone exhibited a repellent activity against this insect at the higher doses tested (285.7 ng/cm2), demonstrating their potential as repellents for this species.
21 citations
TL;DR: Each insect community is distinctive among elevations and months and that diversity of flowering plants, precipitation, and elevation influence their structure and composition, indicating that conservation strategies should involve protection of forest cover at the whole elevation gradient, in order to preserve common and exclusive components of diversity and consequently the mosaic of plant–pollinator interactions.
Abstract: The determinants of diversity are a central issue in ecology, particularly in Andean forests that are known to be a major diversity hotspot for several taxa. We examined the effect of abiotic (elevation and precipitation) and biotic (flowering plant diversity) factors considered to be decisive causal factors of diversity patterns on anthophyllous insect communities on mountain forest. Sampling was carried out in 100-m transects at eight elevational levels and during a period of 8 months. All flowering plants in the understory and their flowering visitors were recorded. Species richness and diversity were estimated for each elevation and month. Diversity of flowering plants, elevation, and precipitation were used as independent variables in multiple regressions against insect diversity. The evaluated abiotic and biotic factors had contrasting effects on insect diversity: a significant decrease on insect diversity occurred at high elevation and dry months (i.e., threshold effect), while it showed a positive relationship with flowering plant diversity through time (i.e., linear effect), but not along elevation. Rapid turnover of species of both interacting guilds was observed every 100-m altitude and month. Local insect communities were also divided functionally depending on the plant family they visit. These results indicate that each insect community is distinctive among elevations and months and that diversity of flowering plants, precipitation, and elevation influence their structure and composition. Thus, conservation strategies should involve protection of forest cover at the whole elevation gradient, in order to preserve common and exclusive components of diversity and consequently, the mosaic of plant–pollinator interactions.
20 citations
TL;DR: The flowering of Z. nummularia was gradual, and was characterized by some flowers that opened and secreted nectar early before sunrise, whereas other flowers remained opened until sunrise, with 83% of nectar secreted in the first day.
Abstract: Ziziphus trees are of economic importance due to their aggregated value (source of fruits and timber) and are the most important melliferous plants in the Arabian Peninsula. Interaction between honeybees and Ziziphus nummularia was investigated by assessing foraging, flower phenology, nectar secretion, and honey potential. It is demonstrate that both the native Apis mellifera jemenitica Ruttner and the exotic Apis mellifera carnica Pollmann foraged on Z. nummularia flowers. Bee foraging for nectar and pollen was low (2 ± 0.7 workers/200 flowers/3 min) during early morning and increased to a peak in the afternoon (100 ± 15 workers/200 flowers/3 min). Remarkable foraging activity was recorded during high temperature (35°C) and low humidity (20%) conditions. Foraging for nectar collection was more distinct than that for pollen. The flowering of Z. nummularia was gradual, and was characterized by some flowers that opened and secreted nectar early before sunrise, whereas other flowers remained opened until sunrise. The flowers lasted 2 days, with 83% of nectar secreted in the first day. The peak of nectar secretion was recorded at noon under hot and dry conditions. The lowest amount of nectar was secreted during sunrise under mild temperature (24°C) and humidity (31%) conditions. Under optimum conditions, it is assumed that the average sugar mass was 0.321 ± 0.03 mg TSS/flower, while the total sugar mass was 27.65 ± 11 g/tree. The average honey production potential of tested Z. nummularia was approximately 2.998 kg/tree and 749.475 kg/ha in the main flowering season.
18 citations
TL;DR: The small tomato borer Neoleucinodes elegantalis completed its life cycle at temperatures between 15°C and27°C, indicating that it can remain active throughout the year in the subtropical region of Brazil, and temperatures above 27°C are deleterious to the fertilization/embryonic development of the studied population of N. elegantalis.
Abstract: The small tomato borer Neoleucinodes elegantalis (Guenee) (Lepidoptera: Crambidae) is one of the major pests of solanaceous in Central and South America. Little is known about the role of temperature on the biological traits of this species. Development time of the immature stages and longevity and reproduction of adults of N. elegantalis at constant temperatures (15, 20, 25, 27, and 30 ± 1°C) were determined when larvae were fed on fruits of the tomato hybrid “Paronset.” Neoleucinodes elegantalis completed its life cycle at temperatures between 15°C and 27°C, indicating that it can remain active throughout the year in the subtropical region of Brazil. The temperature threshold (T
t) was 8.8°C for the egg stage and 7.7°C for the larval and pupal stages. The small tomato borer required 588.2 degrees-day for its full development. At 30°C, the eggs were infertile, indicating that temperatures above 27°C are deleterious to the fertilization/embryonic development of the studied population of N. elegantalis. The number of generations of N. elegantalis per year in the Brazilian subtropical region is lower than for populations developing in warmer tropical areas. A relationship was found between the number of generations and the increase in latitude.
17 citations
TL;DR: Geostatistics and Geographic Information Systems are employed to measure the range of spatial correlation of G. molesta in order to define the optimum sampling distance for performing spatial analysis and to determine the current distribution of the pest in peach orchards of southern Uruguay.
Abstract: The oriental fruit moth, Grapholita molesta (Busck), is the most serious pest in peach, and several insecticide applications are required to reduce crop damage to acceptable levels. Geostatistics and Geographic Information Systems (GIS) are employed to measure the range of spatial correlation of G. molesta in order to define the optimum sampling distance for performing spatial analysis and to determine the current distribution of the pest in peach orchards of southern Uruguay. From 2007 to 2010, 135 pheromone traps per season were installed and georeferenced in peach orchards distributed over 50,000 ha. Male adult captures were recorded weekly from September to April. Structural analysis of the captures was performed, yielding 14 semivariograms for the accumulated captures analyzed by generation and growing season. Two sets of maps were constructed to describe the pest distribution. Nine significant models were obtained in the 14 evaluated periods. The range estimated for the correlation was from 908 to 6884 m. Three hot spots of high population level and some areas with comparatively low populations were constant over the 3-year period, while there is a greater variation in the size of the population in different generations and years in other areas.
TL;DR: Results revealed that hexane, chloroform and ethyl acetate extracts of C. guianensis showed larvicidal and pupicidal activities against S. litura, and this fraction could be used to develop botanical formulation to control agricultural pests.
Abstract: Laboratory experiments were conducted to find out the efficacy of different crude extracts and fractions of Couroupita guianensis (Lecythidaceae) against Spodoptera litura (Fabricius). Results revealed that hexane, chloroform and ethyl acetate extracts of C. guianensis showed larvicidal and pupicidal activities against S. litura. Maximum larvicidal activity (68.66%) was observed in hexane extract at 5.0% concentration followed by chloroform and ethyl acetate extracts, and least LC50 value of 2.64% was observed in hexane extract. A 100% pupicidal activity was observed in hexane extract. Based on the efficacy of crude extracts, the effective crude extract (hexane extract) was further fractionated and subjected to screening for biological activities against S. litura. Among the eight fractions isolated from the hexane extract, fraction 8 showed maximum antifeedant activity (81. 8%) and larvicidal activity (76.9%) at 1000-ppm concentration; this fraction showed least LC50 value of 375.92 ppm for larvicidal activity. Cent per cent pupicidal activity was recorded. Reduced midgut and hemolymph protein contents were observed at 1000 ppm of fraction 8. Histopathological studies revealed that fraction 8 severely damaged the midgut cells of S. litura. This fraction could be used to develop botanical formulation to control agricultural pests.
TL;DR: Infested trees were treated with imidacloprid and thiamethoxam, and subterranean termites were effectively controlled during the 9-year study, which showed that the higher the CBH value, theHigher the percentage of internal damage by C. gestroi.
Abstract: Urban tree deterioration is a common problem all over the world. Inappropriate plant species choice and inadequate planting may lead to micro and macro organism attacks, such as pests and diseases. Subterranean termite damage is common and may promote tree falls. In order to help urban forestry planning, this work was carried out for 9 years on 1477 street trees in a neighborhood in the city of Sao Paulo, Brazil. Plants were identified to species, grouped as native, exotic plants, and palm trees, and their measures of circumference at breast height (CBH) were taken, in order to evaluate if subterranean termite damages are related to tree size and plant group. Four subterranean termite species were identified infesting up to 27% of the plants, with Coptotermes gestroi (Wasmann) being the most common. Palm trees were not damaged by subterranean termites, while native plants are the most susceptible, especially Caesalpinia pluviosa var. peltophoroides (Fabaceae). Among the native plants monitored C. pluviosa var. peltophoroides, Caesalpinia ferrea var. leiostachya, Erythrina speciosa, Piptadenia gonoacantha (Fabaceae), Gochnatia polymorpha (Asteraceae), Tibouchina granulosa (Melastomataceae), and Handroanthus spp. (Bignoniaceae), the latter was the least damaged. Exotic plants were also susceptible with the exception of Lagerstroemia indica (Lythraceae) and Platanus acerifolia (Platanaceae). Correlation analysis showed that the higher the CBH value, the higher the percentage of internal damage by C. gestroi. Infested trees were treated with imidacloprid and thiamethoxam, and subterranean termites were effectively controlled during the 9-year study.
TL;DR: Chlorpyrifos (positive control) caused high adult parasitoid mortality in all bioassays, and while T. pretiosum and the tested entomopathogens may be used simultaneously in integrated pest management programs, the use of chlorpyrIFos should be avoided.
Abstract: The selectivity of various entomopathogens and one insecticide (chlorpyrifos = positive control) to Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) was evaluated in the laboratory, using the protocol established by the Working Group on "Pesticides and Beneficial Organisms" of the IOBC. The evaluated parameters were parasitism (%), adult emergence (%), and product repellency to the parasitoid when sprayed on host eggs prior to parasitism (free-choice and no-choice tests). Most of the studied entomopathogens (Bacillus thuringiensis var. kurstaki, Bacillus thuringiensis var. aizawai, Beauveria bassiana, Metarhizium anisopliae, and Trichoderma harzianum) had no effects on biological parameters and were classified as harmless to T. pretiosum. Emergence of parasitoids (progeny viability) was reduced, but remained above 90%, when host eggs were sprayed with Baculovirus anticarsia prior to parasitism in the free-choice test, and B. anticarsia was therefore considered harmless. Chlorpyrifos (positive control) caused high adult parasitoid mortality in all bioassays. While T. pretiosum and the tested entomopathogens may be used simultaneously in integrated pest management programs, the use of chlorpyrifos should be avoided.
TL;DR: It can be concluded that the most optimum environmental conditions of the tested nematodes to elicit their infectivity against late third instars of C. capitata were sandy soil with 10% moisture level, ambient temperature of 25°C, and no exposure to UV.
Abstract: Late third instars of the medfly, Ceratitis capitata (Wied.), migrate from the host fruit into the soil and leaf litter beneath host trees, where they may become a target for entomopathogenic nematodes (EPNs). The effects of ultraviolet (UV) light, temperature, soil type (texture), and soil moisture level on infectivity of the four tested EPNs Heterorhabditis bacteriophora AS1, H. bacteriophora HP88, Steinernema carpocapsae ALL, and Steinernema riobrave ML29 to late third instars of C. capitata were evaluated. Biochemical alterations induced by the most virulent nematodes were quantified. The nematode infectivity decreased with increase in exposure time to UV light, whereas it increased with increase in temperature. Infectivity increased in sandy soil, whereas it decreased in silt and clay soils. Soils with high moisture levels decreased infectivity. Based on the 50% lethal concentration (LC50), H. bacteriophora AS1 and S. carpocapsae ALL were the most virulent heterorhabditid and steinernematid nematodes, respectively, with the highest virulence for H. bacteriophora AS1. The nematodes caused significant decline in total protein and cholesterol content of larvae and caused reduced activity of transaminases and phosphatases. In contrast, they significantly enhanced total glucose content. It can be concluded that the most optimum environmental conditions of the tested nematodes to elicit their infectivity against late third instars of C. capitata were sandy soil with 10% moisture level, ambient temperature of 25°C, and no exposure to UV. The EPNs tested can affect late third instars of C. capitata by targeting different biochemical molecules in different metabolic pathways. The interaction between them and the host larvae appears to be primarily nutritional.
TL;DR: The wing veins of male Eulaema nigrita Lepeletier (Apidae: Euglossini) bees were measured to evaluate whether the bees sampled in agriculture (AG) areas suffer higher fluctuating asymmetry (FA) than those sampled in Cerrado areas in the Brazilian state of Goiás.
Abstract: Among other human-related activities, habitat loss and fragmentation are currently ranked as the most important environmental features affecting the persistence of animal and plant populations in landscapes, as well as the maintenance of ecological processes and services. Since these processes are also capable of affecting the ontogenetic development of species inhabiting those landscapes, here we measured the wing veins of male Eulaema nigrita Lepeletier (Apidae: Euglossini) bees in order to evaluate whether the bees sampled in agriculture (AG) areas suffer higher fluctuating asymmetry (FA) than those sampled in Cerrado (CE) areas in the Brazilian state of Goias. We believe that individuals sampled in CE areas would be less asymmetric than those sampled in AG areas, given a potential higher exposure of these specimens to environmental stresses (mostly pesticides). However, we did not observe a significant trend in the FA measures we obtained, although three wing measures were bigger for bees from CE areas. The lack of significant effects of FA may be related to inherent bionomic features of E. nigrita. For instance, given their high individual dispersal abilities, the individuals we analyzed may have developed in different areas than those where they were sampled. Their generalist feeding behavior may also have given them a higher resistance to environmental perturbations, buffering the normal development of immatures even in areas with local high environmental stress. Nonetheless, higher death rates of individuals from anthropic areas may also have killed the developing immatures of E. nigrita before they reached adulthood consequently equalizing our sampled estimates.
TL;DR: The longipalpus-group of Chrysotus Meigen is reviewed and comprises eight species that were introduced in the Afrotropical, Australasian, Oriental and Palaearctic regions and Illustrations of the hypopygium and ovipositor, photos of the male palpus and a key to species of the group are provided.
Abstract: The longipalpus-group of Chrysotus Meigen is reviewed and comprises eight species: Chrysotus coquitos n. sp. (Mexico), Chrysotus crosbyi Van Duzee (Eastern US, Bermuda, Cuba, Puerto Rico and Brazil; introduced in Australasian Region), Chrysotus longipalpus Aldrich (=Chrysotus sagittarius Van Duzee, n. syn.; Eastern US, Saint Vincent, Grenadas and Brazil; introduced in the Afrotropical, Australasian, Oriental and Palaearctic regions), Chrysotus miripalpus Parent (Costa Rica and Brazil), Chrysotus neopedionomus n. sp. (Brazil), Chrysotus pachystoma n. sp. (Belize), Chrysotus xiphostoma Robinson (Dominica and Saint Lucia), and Chrysotus zumbadoi n. sp. (Costa Rica). Lectotype and paralectotypes are designated for Chrysotus pallidipalpus Van Duzee, and a neotype for C. miripalpus. Illustrations of the hypopygium and ovipositor, photos of the male palpus and a key to species of the group are provided.
TL;DR: Diversity, species richness, and abundance were highest in the forest fragment and in spring and summer captures, and the composition of the assemblage was different among habitats.
Abstract: The aims of this study were to characterize the fauna of dung beetles and analyze their spatial and temporal diversity in a cattle ranch in the province of Chaco. Seven surveys were conducted in three environmental units: a forest fragment, a cattle pasture, and an open grassland. The efficiency of the sampling was assessed with non-parametric richness estimators, and attributes of the assemblage were evaluated. The species composition and the abundance distribution in each of the environmental units studied were compared using rank-abundance curves. The indicator value of each species was measured with the IndVal method. The relationship between richness, abundance, and environmental variables (temperature, precipitation, and relative humidity) was calculated by multivariate multiple regression analysis. A total of 3,356 adult individuals belonging to 29 species of the subfamily Scarabaeinae and to five species of Aphodiinae were captured. Dichotomius nisus (Olivier), Trichillum externepunctatum (Preudhomme), Canthon podagricus (Harold), Onthophagus hirculus (Mannerheim), Pseudocanthon aff. perplexus, Ontherus sulcator (Fabricius), and Ataenius platensis (Blanchard) were the most abundant. Diversity, species richness, and abundance were highest in the forest fragment and in spring and summer captures. Between 94% and 97% of the species present in the entire landscape were recorded. According to the analysis of similarity, the composition of the assemblage was different among habitats. Eurysternus caribaeus (Herbst), Eurysternus aeneus (Genier), and O. sulcator were indicators of the forest. In the three units, the coprophagous species represented more than 60% of the total species number. The rainfall regime, the temperature, and the heterogeneous use of the environmental units influenced the structure of dung beetle assemblages.
TL;DR: It was verified that the nectar loads of the individuals that made either constant or non-constant flights did not differ in the number of pollen grains they contained, which would indicate that the probability of changing between plant species during nectar collection is independent of the foraging trip duration.
Abstract: The flower constancy (the visit to a single plant species during a foraging trip) in pollinator insects is a theme widely discussed in behavioral ecology and has an important implication in the evolution of angiosperms. This behavior was studied in the bumblebees Bombus atratus Franklin and Bombus bellicosus Smith through palynological analysis of the nectar and pollen loads of individuals captured while foraging in a restricted area. In both species, there were more individuals with constant flights than with non-constant ones, although in the nectar loads of B. atratus there were no significant differences between individuals with each flight types. It was verified that the nectar loads of the individuals that made either constant or non-constant flights did not differ in the number of pollen grains they contained. Considering this measurement as an estimate for flight duration, the results would indicate that the probability of changing between plant species during nectar collection is independent of the foraging trip duration. In both species, most individuals who collected nectar and/or pollen from more than one plant species visited just two plant species. In these cases, the pollen of one plant species was predominant. In the bumblebees in which it was possible to analyze nectar and pollen loads, the botanical origin of both resources was the same or they shared the principal species (with the exception of two individuals), showing that bumblebees do not often use a botanical source in an exclusive way to collect nectar and another to collect pollen.
TL;DR: The results suggest that the effects of global warming over dung beetle communities will be difficult to predict because of species-specific responses to global warming.
Abstract: To understand the effects of global warming in tropical insect communities, it is necessary to comprehend how such communities respond to different abiotic factors that covariate with altitude. In this study, we partially answer this question applied to dung beetle communities distributed along an altitudinal gradient. The sampling was conducted in seven stations 100 m apart each in altitude in a dry mountain scrub in southern Ecuador. A total of 7422 individuals belonging to six species were captured. Canthon balteatus Boheman was the most abundant with 6502 individuals, and Onoreidium ohausi (Arrow) was the least abundant with 20 individuals. We found significant changes in the structure of the dung beetle communities with altitude. Two abiotic factors showed a relationship with the abundance pattern for all species (altitude, Z = 0.011, p < 0.01, and temperature, Z = 0.859, p < 0.01). Canthon balteatus Boheman showed a positive relationship with altitude (Z = 1.422, p < 0.001) and temperature (Z = 1.121, p < 0.001), Dichotomius problematicus (Luederwaldt) a positive relationship with precipitation (Z = 0.113, p < 0.001), and Malagoniella cupreicollis (Waterhouse) a positive relationship with temperature (Z = 0.668, p < 0.001) and negative with precipitation (Z = −0.189, p < 0.001). Phanaeus achilles Boheman, Onthophagus sp., and O. ohausi (Arrow) did not show any relationship with the studied variables, nor was the richness correlated with the studied variables. These results suggest that the effects of global warming over dung beetle communities will be difficult to predict because of species-specific responses to global warming.
TL;DR: It is demonstrated that although gravid females contain phytoplasmas, they are not able to transmit them to their progeny, confirming that transovarial transmission of ‘Ca. curtulus ulmi’ does not occur in A.Curtulus.
Abstract: 'Candidatus Phytoplasma ulmi' (Elm yellows, 16SrV-A), transmitted by Amplicephalus curtulus Linnavuori & DeLong (Hemiptera: Cicadellidae), has been found in native Chilean plants, and transovarial transmission has been considered as a possible form of transmission. An analysis to detect the presence of 'Ca. Phytoplasma ulmi' and other phytoplasmas in A. curtulus eggs, nymphs of the first and fifth instars were carried out in two experiments using nested PCR and DNA sequencing. The first experiment showed the natural acquisition of phytoplasma by adult females, and the second demonstrated the acquisition of phytoplasma in controlled conditions. Results showed that eggs and the first and fifth instars were not positive for phytoplasmas in nested PCR. 'Candidatus Phytoplasma ulmi' was detected and identified on average 10 and 47% of the adult females used in experiments 1 and 2, respectively. Other phytoplasma (X-disease group) was also found in adult females used in the experiment 1. We demonstrate that although gravid females contain phytoplasmas, they are not able to transmit them to their progeny, confirming that transovarial transmission of 'Ca. Phytoplasma ulmi' does not occur in A. curtulus.
TL;DR: Scanning electron microscopy was used to investigate the typology, morphology, and distribution of sensilla on the antennae and ovipositor of H. hippophaecolus to provide morphological evidence to facilitate a better understanding of the host location, mate finding, and Oviposition processes of this important species.
Abstract: Holcocerus hippophaecolus Hua et al (Lepidoptera: Cossidae) is an important boring pest that damages the sea buckthorn Hippophae rhamnoides. Larvae of H. hippophaecolus cause major losses of this shrub in Northern China, with severe economic and ecological consequences. In this study, we used scanning electron microscopy to investigate the typology, morphology, and distribution of sensilla on the antennae and ovipositor of H. hippophaecolus. In total, seven subtypes of sensilla were found on the antennae, i.e., chaetica, trichodea (two subtypes), basiconica (two subtypes), coeloconica, and Bohm bristles. In addition, three types of sensilla were detected on the ovipositor, i.e., chaetica, trichodea, and basiconica. The identification of these sensilla types could provide morphological evidence to facilitate a better understanding of the host location, mate finding, and oviposition processes of this important species.
TL;DR: Essential oil from P. pseudocaryophyllus leaves is an interesting source of compounds with grain-protectant properties and should be analyzed in future studies aiming to develop new bioinsecticides to use in the IPM of stored grains.
Abstract: Plant-based insecticides can play an important role in integrated insect pest management (IPM), especially in protecting stored grains. The aim of this study was to evaluate the bioactivity of derivatives (powder, ethanolic extract, and essential oil (EO)) from the leaves of Pimenta pseudocaryophyllus (Myrtaceae), a Brazilian native species, against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), the main insect pest of stored corn. The powder and essential oil prepared from leaves showed a repellent effect. Moreover, the EO exhibited promising insecticidal activity through residual contact (LC50 = 1522 mg kg(-1)) and significantly decreased the F 1 progeny and the percentage of damaged grains. However, the essential oil obtained from P. pseudocaryophyllus leaves did not result in significant mortality of S. zeamais adults after 72 h of exposure by fumigation in concentrations up to 400 μL L(-1) of air. Based on GC-MS analysis, 20 compounds were identified in the essential oil of P. pseudocaryophyllus leaves, being chavibetol (38.14%), methyl eugenol (11.35%), and terpinolene (9.17%) as the major constituents. Essential oil from P. pseudocaryophyllus leaves is an interesting source of compounds with grain-protectant properties and should be analyzed in future studies aiming to develop new bioinsecticides to use in the IPM of stored grains.
TL;DR: The testis morphology and spermatogenesis of the sugarcane borer is described using light, transmission, and scanning electron microscopies and the spermatozoa morphology is similar to that of other Lepidoptera.
Abstract: In the present study, we describe the testis morphology and spermatogenesis of the sugarcane borer, one of the most destructive pests of sugarcane, using light, transmission, and scanning electron microscopies. Diatraea saccharalis (F.) larvae have paired, kidney-shaped testes that are limited externally and divided into four follicles by tunica cells. The adults have two fused whitish and spherical testes that are divided into eight follicles and are composed of spermatogonia, spermatocyte, spermatid, and sperm bundles. The spermatogonia and spermatocyte cysts are located at the apical extremity of the follicle, while the spermatid cysts and sperm bundles are located at the basal extremity of the follicle. Inside of the cysts, which are formed by the somatic cells, the germ line cells develop synchronously and are interconnected by cytoplasmic bridges. Each cyst contains only apyrene or eupyrene, and none of the cysts contain both of the cells. The inner part of the apyrene cyst consists of an electron-dense cap as opposed to a nucleus. The eupyrene sperm contains a nucleus, acrosome, and reticular and lacinate appendages. Both of the sperm types have a “9 + 9 + 2” axoneme and two mitochondrial derivatives at the tail region. The spermatogenesis process and spermatozoa morphology are similar to that of other Lepidoptera.
TL;DR: Leaf beetles are evaluated as habitat quality bioindicators in a system with varying intensities of human impacts and different phyto-physiognomies (from open field to forests) to allow for a better understanding of Chrysomelidae response to environmental disturbance.
Abstract: In landscape mosaics, species may use different vegetation types or be restricted to a single vegetation type or land-use feature highlighting the importance of the interaction of species requirements and environmental heterogeneity. In these systems, the determination of the overall pattern of β-diversity can indicate the importance of the environmental heterogeneity on diversity patterns. Here, we evaluate leaf beetles (Coleoptera: Chrysomelidae) as habitat quality bioindicators in a system with varying intensities of human impacts and different phyto-physiognomies (from open field to forests). We collected 1117 leaf beetles belonging to 245 species, of which 12 species and 5 genus were considered possible bioindicators based on IndVal measures. Higher species richness was observed in forests and regenerating fields, and habitats with lower species richness included pastures, mines, and veredas. Natural fields, regenerating fields, natural cerrado, and forest had higher values of β-diversity. Bioindicator systems that include not only species richness and abundance but also assemblage composition are needed to allow for a better understanding of Chrysomelidae response to environmental disturbance.
TL;DR: Adult survival was affected by the prey type, as 75% of C. externa control adults remained alive at an age of 30 days compared to 51 and 54% for those fed on PLRV-uninfected and infected aphids, respectively.
Abstract: The aim of this study was to evaluate the biological parameters of Chrysoperla externa (Hagen) while feeding on Myzus persicae (Sulzer) acting as a vector of potato leafroll virus (PLRV). In laboratory experiments, three different diets were offered ad libitum to C. externa during the larval period: M. persicae fed on PLRV-infected potato leaves, M. persicae fed on uninfected potato leaves, and eggs of the factitious prey Anagasta kuehniella (Zeller) as the control. The following parameters were studied: the developmental time and survival rate of the larval and pupal stages, the sex ratio, the proportion of fertile females, female fecundity and egg viability, and the survival curve of the first 30 days after adult emergence. PLRV-infected aphids influenced the C. externa larval developmental time and survival compared to PLRV-uninfected aphids and A. kuehniella eggs. The pupal developmental time of C. externa was shorter when fed on aphids compared to A. kuehniella eggs, but no differences were recorded between the PLRV-infected and uninfected aphid diets. Additionally, no differences were observed for pupal survival and reproduction. However, adult survival was affected by the prey type, as 75% of C. externa control adults remained alive at an age of 30 days compared to 51 and 54% for those fed on PLRV-uninfected and infected aphids, respectively.
TL;DR: The numerical variation of psyllid population is described and these variations to the abiotic and biotic factors that may naturally regulate the population of this pest are correlated with the main factors that regulate its population.
Abstract: Eucalypts host a variety of insect pests among which the psyllid Blastopsylla occcidentalis Taylor is responsible for the degeneration of eucalypt seedlings. This psyllid is present in Cameroon, but no record has been published on the study of its population dynamics and the main factors that regulate its population. Our study aimed to describe the numerical variation of psyllid population and to correlate these variations to the abiotic and biotic factors that may naturally regulate the population of this pest. This study was carried out in Yaounde (Cameroon) from August 2009 to July 2011. The survey took place once a week on 1-year-old 111 eucalypts. During the 2 years of study, a total of 52,341 males and 64,725 females were collected. The population of B. occidentalis showed three periods of psyllid outbreaks each year. Six and five psyllid generations were observed during the first and the second years, respectively. Among the climatic factors, the increase of relative humidity and rainfall led to a decrease of the number of psyllids on the host plant. The number of new buds on host plants was positively correlated with the number of psyllids infesting. Psyllid parasitoids and predators were identified. These results constitute an important step for the elaboration of an integrated pest management against the eucalypt psyllid in Cameroon.
TL;DR: Investigation of the potential pro- and anticonvulsant effects of the venom from the ant Dinoponera quadriceps in Swiss mice demonstrates that D. quad riceps venom might be potential source of new pro-and anticonVulsants molecules.
Abstract: Epilepsy affects at least 50 million people worldwide, and the available treatment is associated with various side effects. Approximately 20–30% of the patients develop seizures that persist despite careful monitored treatment with antiepileptic drugs. Thus, there is a clear need for the development of new antiepileptic drugs, and the venoms can be an excellent source of probes. In this context, while there are studies on venoms from snakes, scorpions, and spiders, little is known regarding venom from ants. The aim of this study was to investigate the potential pro- and anticonvulsant effects of the venom from the ant Dinoponera quadriceps (Kempf) in Swiss mice. After the injection of the crude venom (DqTx—5, 50, and 500 mg/mL) in the lateral ventricle of mice, we observed a reduction of exploration and grooming behaviors, as well as an increase in immobility duration. In addition, the crude venom induced procursive behavior and tonic-clonic seizures at the highest concentration. Conversely, the preadministration of the denatured venom (AbDq) at the concentration of 2 mg/mL protected the animals against tonic-clonic seizures (66.7%) and death (100%) induced by administration of bicuculline. Taken together, the findings demonstrate that D. quadriceps venom might be potential source of new pro- and anticonvulsants molecules.
TL;DR: In this article, the authors describe the distribution patterns of lady beetles (adults, larvae, and egg clusters) relative to plants and aphids in eight crop ecosystems in a central region of Brazil.
Abstract: The competitive exclusion hypothesis suggests that coexisting related species using similar resources in nature should partition their realized niches. This hypothesis has direct implications for conservation strategies using biological control, taking into consideration the shifts caused by the introduction of natural enemies in a local community. Such introductions typically lead to disruptions in species interactions and interfere with community structure. In this study, we asked whether community structure of aphidophagous lady beetles is determined by the distribution of specific plants and aphids. To answer this question, we describe the distribution patterns of lady beetles (adults, larvae, and egg clusters) relative to plants and aphids in eight crop ecosystems in a central region of Brazil. We used canonical correspondence analysis to evaluate lady beetle distribution relative to selected habitat variables. Cycloneda sanguinea L., Hippodamia convergens Guerin-Meneville, Harmonia axyridis Pallas, and Eriopis connexa Germar (Coleoptera: Coccinellidae) differed in their use of plants and aphids. The association of egg clusters with specific plants/aphids was stronger than that of larvae or adults. In conclusion, lady beetle species occupied different niches, indicating different patterns of habitat use that may facilitate their coexistence in crop ecosystems. Furthermore, immature individuals had more specific environmental associations than adults, likely because female choice of oviposition sites influences their distribution and thus lady beetle community structure.
TL;DR: The results of this study suggest a relative compatibility between spinosad use and H. hebetor in IPM programs and the off-target effects of pesticides on biological control agents are essential considerations of IPM.
Abstract: The appropriate use of biological agents and chemical compounds is necessary to establish successful integrated pest management (IPM) programs. Thus, the off-target effects of pesticides on biological control agents are essential considerations of IPM. In this study, the effects of lethal and sublethal concentrations of chlorpyrifos and spinosad on the demographic parameters of Habrobracon hebetor (Say) (Hymenoptera: Braconidae) were assessed. Bioassays were carried out on immature and adult stages by using dipping and contact exposure of dry pesticide residue on an inert material, respectively. The lethal concentration (LC)50 values of chlorpyrifos and spinosad were 3.69 and 151.37 ppm, respectively, on the larval stage and 1.75 and 117.37 ppm, respectively, on adults. Hazard quotient (HQ) values for chlorpyrifos and spinosad were 400 and 2.2, respectively, on the larval stage and 857.14 and 2.84, respectively, on adults. A low lethal concentration (LC30) was used to assess the sublethal effects of both pesticides on the surviving females. In each treatment, 25 survivors were randomly selected and transferred into 6-cm Petri dishes. Adults were provided daily with last instars of Anagasta kuehniella (Zeller) as a host until all of the females died. The number of eggs laid, percent of larvae hatched, longevity, and sex ratio were recorded. Stable population growth parameters were estimated by the Jackknife method. In control, chlorpyrifos, and spinosad treatments, the intrinsic rates of increase (r m) values were 0.23, 0.10, and 0.21, respectively. The results of this study suggest a relative compatibility between spinosad use and H. hebetor. Finally, further studies should be conducted under natural conditions to verify the compatibility of spinosad with H. hebetor in IPM programs.