Differential responses to double-stranded RNA injection and feeding in Mormon cricket (Orthoptera: Tettigoniidae).

The Mormon cricket, Anabrus simplex, is a flightless katydid, one of the major devastating rangeland pests in several states of the western United States. During the past few years, their sudden and periodic outbreaks into massive migratory bands caused significant economic losses to the rangeland forage and agricultural crops, particularly grain crops. Current population management methods rely heavily on broad-spectrum chemical insecticides, which could be toxic to nontargets, and even the targeted species might develop resistance in the long run. Therefore, we assessed the potential of RNA interference (RNAi)-based alternative management strategies that could supplement the current methods. In insects, RNAi efficiency varies with the method of double-stranded RNA (dsRNA) delivery. We tested 2 different methods of dsRNA delivery: injection and oral feeding of dsRNA. The results showed that Mormon crickets are sensitive to injection of dsRNA in a dose-dependent manner, but refractory to the oral feeding of dsRNA. Further, we confirmed the high nuclease activity in the insect midgut. In order to protect the dsRNA from the dsRNase activity and facilitate its uptake in the midgut, we encapsulated dsRNA inside poly lactic-co-glycolic acid (PLGA) nanoparticles and studied its release kinetics and RNAi efficiency by oral feeding. The release kinetics clearly suggested that the PLGA nanoparticle permeates from the insect digestive system to the hemolymph; however, it failed to induce an efficient RNAi response of the targeted genes. In conclusion, our findings suggest the different responses to dsRNA delivery methods in Mormon crickets, and further investigations involving dsRNA stability and its uptake mechanism are required to use RNAi as an alternative Mormon cricket population management strategy.

Studies in Mexican Grasshoppers: Liladownsia fraile, a new genus and species of Dactylotini (Acrididae: Melanoplinae) and an updated molecular phylogeny of Melanoplinae.

Liladownsia fraile gen. nov. sp. nov. Fontana, Mariño-Pérez, Woller & Song (Lila Downs' friar grasshopper) of the tribe Dactylotini (Orthoptera: Acrididae: Melanoplinae) is described from the pine-oak forest of the Sierra Madre del Sur Mountain Range in Oaxaca, Mexico. Taxonomic placement of this new genus is justified based on morphological characters as well as a molecular phylogeny. Information about the probable host plant, phenology, and known localities is also presented. We also present an updated molecular phylogeny of Melanoplinae, which includes representatives of five of the seven recognized tribes. The monophyly of the subfamily and the included tribes is tested and we find Dactylotini to be paraphyletic because of the placement of Hesperotettix Scudder, 1876. We also recover strong close relationships between the new genus and Perixerus Gerstaecker, 1873 and Dactylotum Charpentier, 1845.  

Studies in Mexican Tettigoniidae: a new genus of Copiphorini and the first description of male Conocephalus (Aphauropus) leptopterus Rehn and Hebard and the female of Insara acutitegmina Fontana, Buzzetti, Mariño-Pérez & García García.

A new genus belonging to the katydid tribe Copiphorini (Tettigoniidae: Conocephalinae) is established, Brachycaulopsis gen. nov., collected from the state of Chiapas, Mexico. Also provided are first descriptions for both the male of Conocephalus (Aphauropus) leptopterus Rehn & Hebard, 1915 (Conocephalinae: Conocephalini) and the female of Insara acutitegmina Fontana et al., 2011 (Phaneropterinae: Insarini).

Development of RNAi Methods for the Mormon Cricket, Anabrus simplex (Orthoptera: Tettigoniidae).

Mormon crickets are a major rangeland pest in the western United States and are currently managed by targeted applications of non-specific chemical insecticides, which can potentially have negative effects on the environment. In this study, we took the first steps toward developing RNAi methods for Mormon crickets as a potential alternative to traditional broad-spectrum insecticides. To design an effective RNAi-based insecticide, we first generated a de novo transcriptome for the Mormon cricket and developed dsRNAs that could silence the expression of seven housekeeping genes. We then characterized the RNAi efficiencies and time-course of knockdown using these dsRNAs, and assessed their ability to induce mortality. We have demonstrated that it is possible to elicit RNAi responses in the Mormon cricket by injection, but knockdown efficiencies and the time course of RNAi response varied according to target genes and tissue types. We also show that one of the reasons for the poor knockdown efficiencies could be the presence of dsRNA-degrading enzymes in the hemolymph. RNAi silencing is possible in Mormon cricket, but more work needs to be done before it can be effectively used as a population management method.

Modeling Rangeland Grasshopper (Orthoptera: Acrididae) Population Density Using a Landscape-Level Predictive Mapping Approach.

Since the mid-19th century, grasshoppers have posed a substantial threat to North American rangelands as well as adjacent croplands and have the potential to cost the economy millions of dollars in annual damages. The United States Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) have gone to great lengths to ensure that rangeland grasshopper populations remain below an economic impact threshold across the western United States. However, current grasshopper forecasting efforts by the USDA are based solely on the previous year's grasshopper density and do not take region-specific environmental factors (e.g., climate and topography) into account. To better understand the effects of climate and landscape heterogeneity on rangeland grasshopper populations, we assessed the relationship between grasshopper density survey data from across 56 sites between 2007 and 2017 for four counties in north central Wyoming with 72 biologically relevant geographic information system (GIS)-based environmental variables. A regression model was developed to predict mean adult grasshopper density from 2012 to 2016, which was then used to forecast grasshopper density in 2017. The best-fit predictive model selected using Akaike's Information Criterion (AICc) explained 34.5% of the variation in mean grasshopper density from 2012 to 2016. October precipitation and past mean grasshopper density from 2007 to 2011 were among the best predictors of mean grasshopper density in 2012-2016. Our results also suggest that rangelands in central Sheridan County, southwest Johnson County, and southeast Washakie County are more prone to grasshopper outbreaks. Most importantly, this study demonstrated that both biotic and abiotic environmental variables influence grasshopper density and should be considered in future forecasting efforts.

Taxonomic notes on the Australian skyhopper genus Kosciuscola Sjstedt (Orthoptera: Acrididae: Oxyinae).

The Australian skyhopper genus Kosciuscola Sjstedt consists of brachypterous species that inhabit the Australian alpine and subalpine region. The genus used to include 5 species and 1 subspecies, but according to a recent phylogenomic study, there could be as many as 14 species in the genus, that are genetically and geographically isolated from each other. This study represents the first step in describing and documenting the diversity of this interesting genus. In this study, we redefine the type species K. tristis, and elevate its subspecies K. tristis restrictus as a valid species on the basis of distinct morphological traits, geographical isolation, and phylogenomic evidence.

Studies in Mexican Grasshoppers: A new species of Pedies Saussure (Acrididae: Melanoplinae) with comments on the unusual blue coloration on the abdomens of females and live specimen images for three other congenerics.

A new species of Melanoplinae (Orthoptera: Acrididae) is described from Central Mexico: Pedies andreae sp. nov. Fontana, Mariño-Pérez, Woller and is added to the 12 existing species. Taxonomic placement of this species is justified based on distinct morphology and comparisons with congeneric species are provided. Additionally, species in this genus are associated with higher elevations (1,700 to 3,700 masl) that possess larger fluctuations in temperatures. We observed that females of P. andreae sp. nov. exhibit blue coloration on their abdomens and we discuss the possible reasons for this peculiar pigmentation. Interestingly, we did not observe this coloration in males. Finally, images are provided for three live previously described species of Pedies.

Investigating the functional morphology of genitalia during copulation in the grasshopper Melanoplus rotundipennis (Scudder, 1878) via correlative microscopy.

We investigated probable functions of the interacting genitalic components of a male and a female of the flightless grasshopper species Melanoplus rotundipennis (Scudder, 1878) (frozen rapidly during copulation) via correlative microscopy; in this case, by synergizing micro-computed tomography (micro-CT) with digital single lens reflex camera photography with focal stacking, and scanning electron microscopy. To assign probable functions, we combined imaging results with observations of live and museum specimens, and function hypotheses from previous studies, the majority of which focused on museum specimens with few investigating hypotheses in a physical framework of copulation. For both sexes, detailed descriptions are given for each of the observed genitalic and other reproductive system components, the majority of which are involved in copulation, and we assigned probable functions to these latter components. The correlative microscopy approach is effective for examining functional morphology in grasshoppers, so we suggest its use for other animals as well, especially when investigating body regions or events that are difficult to access and understand otherwise, as shown here with genitalia and copulation. J. Morphol. 278:334-359, 2017. © 2017 Wiley Periodicals, Inc.

Phylogeny of locusts and grasshoppers reveals complex evolution of density-dependent phenotypic plasticity.

Locusts are grasshoppers that can form dense migrating swarms through an extreme form of density-dependent phenotypic plasticity, known as locust phase polyphenism. We present a comprehensive phylogeny of the genus Schistocerca, which contains both non-swarming grasshoppers and swarming locusts. We find that the desert locust, S. gregaria, which is the only Old World representative of the genus, is the earliest diverging lineage. This suggests that the common ancestor of Schistocerca must have been a swarming locust that crossed the Atlantic Ocean from Africa to America approximately 6 million years ago, giving rise to the current diversity in the New World. This also implies that density-dependent phenotypic plasticity is an ancestral trait for the genus. Through ancestral character reconstruction of reaction norms, we show that colour plasticity has been largely retained in most species in the genus, but behavioural plasticity was lost and regained at least twice. Furthermore, we show that swarming species do not form a monophyletic group and non-swarming species that are closely related to locusts often express locust-like plastic reaction norms. Thus, we conclude that individual reaction norms have followed different evolutionary trajectories, which have led to the evolutionary transition between grasshoppers and locusts - and vice versa.

Studies in Mexican Grasshoppers: Three new species of Dactylotini (Acrididae: Melanoplinae) from Mexico and a review of existing conspecifics with comments on their geographical distributions.

Three new species of the tribe Dactylotini (Acrididae: Melanoplinae) are described from Central and Southern Mexico. 1) Dasyscirtus monicae sp. nov. Fontana, Mariño-Pérez, Sanabria-Urbán, & Woller is described from the eastern portion of the Balsas River Basin and the outer slope of the Mexican Volcanic Belt; 2) Perixerus obscurus sp. nov. Fontana, Mariño-Pérez, Sanabria-Urbán, & Woller is described from the Sierra Norte de Oaxaca mountain range; and 3), Perixerus triqui sp. nov. Fontana, Mariño-Pérez, Sanabria-Urbán, & Woller is described from the Sierra Madre del Sur mountain range and towards the Pacific Coast of Oaxaca. Taxonomic placement of these species is justified based on distinct morphology and comparisons with congeneric species are provided. Finally, we provide a biogeographical explanation for the distribution of the species in both genera.