Response of grasshoppers (Orthoptera: Acrididae) to livestock grazing in southeastern Arizona: differences between seasons and subfamilies

Summary Grasshopper densities were compared between grazed and ungrazed semidesert grassland sites in southeastern Arizona. Bouteloua-dominated perennial grass cover was about 1.5 times greater on the livestock exclosure. Grasshoppers were 3.7 times more abundant on the protected area in the summers of 1983 and 1984, when dominant species were grass-feeding members of the subfamily Gomphocerinae. In fall 1984, grasshoppers were 3.8 times more common on the grazed site, when dominants were mainly herb-feeders in the subfamily Melanoplinae. These results indicate important seasonal and taxonomic differences in the responses of grasshoppers to the activities of vertebrate grazers.     

Prey location by Oechalia schellembergii

A total of 548 spiders (Gnaphosidae, Clubionidae, Thomisidae, Philodromidae, Salticidae, Lycosidae, Pisauridae, Linyphiidae) from three sand dune grassland sites were tested serologically for feeding on the grasshoppers, Chorthippus brunneus (Thunberg) and Myrmeleotettix maculatus (Thunberg). Lycosidae were the most commonly tested species and gave the greatest proportion of positive tests. Laboratory observations suggest that predation in the field was predominantly on first instar grasshoppers.

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Résumé Afin d'améliorer la connaissance de l'importance des prédateurs dans la biologie des populations de criquets (Orthoptères; Acrididae), les araignées de trois pelouses sur dunes de sable ont été examinées sérologiquement pour estimer leur consommation des populations sympatriques de Chorthippus brunneus Thunberg et Myrmeleotettix maculatus Thunberg. Au total, 548 araignées (Gnaphosidae, Clubionidae, Thomisidae, Philodromidae, Salticidae, Lycosidae, Pisauridae, Linyphiidae) ont été récoltées à la main ou par piège pendant la période d'éclosion des ufs de criquets. Les Lycosidae ont été le plus fréquemment observées (90,5% de toutes les récoltes) et ont donné la plus forte proportion d'individus positifs (jusqu'à 32,3%). Les expériences d'alimentation en laboratoire suggèrent que, dans la nature, les Lycosidae sont les plus actives contre les criquets du premier stade.

     

Haemagglutinin activity in the haemolymph of individual Acrididae (grasshopper) specimens

Twenty-four individual grasshopper specimens representing four Melanoplus spp. contained similar broad-spectrum haemolymphatic haemagglutinin. The agglutinin activity showed highest titre toward human ABO and rabbit cells among nine types of erythrocytes tested. Titre values differed between individual insects but agglutination specificity toward different erythrocytes was similar. Agglutination of type-O red cells by individual grasshopper haemolymph was inhibited by 34 of 41 tested carbohydrates, carbohydrate derivatives, alcohols and chelating agents. Individual insects showed similar patterns of haemagglutination inhibition. Non-inhibitory compounds were mannose and mannose derivatives (excepting N-acetylneuraminate), several glucose derivatives, amino sugars and ethanol. The observations indicated that haemolymph from an individual grasshopper contained complex heteroagglutinin activity similar to that found in haemolymph pooled from several insects. Determination of minimal effective inhibitor concentrations confirmed the presence of heteroagglutinin activity primarily directed toward galactose and glucose and related α-linked glycosidic derivatives.     

中国窝蝗属一新种：直翅目：蝗总科：剑角蝗科

本文了剑角蝗科窝蝗属１新种：郑氏窝蝗Ｆｏｖｅｏｌａｔａｃｒｉｓ ｚｈｅｎｇｉ,ｓｐ．ｎｏｖ。,采自甘肃省南县宝瓶河牧场;并据此对属征作了必要的修订,给出了分种检索表。模式标本保存于陕西师范大学动物研究所。     

Sex differentiation studies relating to releaser aggregation pheromones of the desert locust,Schistocerca gregaria

Behavioural responses of nymphs and adults in the gregarious phase of the desert locust,Schistocerca gregaria (Forskal) (Orthoptera: Acrididae) were investigated in a single-chamber bioassay system to a choice of two columns of air, one permeated with airborne volatiles emanating from either sex of nymphs or adults and the other untreated. There was no sexual differentiation in the production of or response to nymphal volatiles. Young adults of either sex did not produce a stimulus with significant activity. Of the older adults, only the males produced the aggregation stimulus to which both sexes were equally responsive. Charcoal-trapped volatiles from the two sexes of nymphs and adults evoked similar aggregation responses. Antennae of the older adults showed significantly higher EAG responses than those of fifth instar nymphs to all four volatile collections, of which volatiles from older adult males were the most stimulatory and evoked the highest EAG amplitudes.     

中国直背蝗属一新种（直翅目：蝗科）

本文记述采自吉林省长白山蝗虫一新种,黄股直背蝗,新种Ｅｕｔｈｙｓｔｉｒａｌｕｔｅｉｆｅｍｏｒａｓｐ．ｎｏｖ．。该新种近似短翅直背蝗Ｅｕｔｈｙｓｔｉｒａｂｒａｃｈｙｐｔｅｒａ（Ｏｃｓｋ．）。     

Evaluation of Nosema locustae (Microsporida) as a control agent of grasshopper populations in Saskatchewan

A quantitative study of the effect of a microsporidan, Nosema locustae, as a control agent against grasshopper populations in Saskatchewan, Canada, revealed that 50% of the populations of Melanoplus sanguinipes, M. packardii, and Camnula pellucida were infected between 4 and 5 weeks (400 to 424 degree-days) after application of the pathogen. Maxima of 95–100% infection were evident between 9 and 12 weeks (600–700 degree-days) after application. The percentage reduction in surviving populations of M. sanguinipes, i.e., those that did not die from natural causes, reached about 20% by the 4th week (400 degree-days) after inoculation, about 50% by the 9th week (600 + degree-days), and a maximum of about 60% by the 12th week (700 degree-days). An exponential relationship was obtained between percentage reduction and percentage infection in all three species. However, a similar percentage infection resulted in different percentage reduction in the populations. Results also revealed that the rate of reduction in populations reached its peak by about 40–80 degree-days before the maximum rate of infection was attained for each species. Egg production in the two Melanoplus species in treated plots was significantly lower (P < 0.05) than in the control plot.     

An improved breeding method for solitarious locusts

In order to unravel the physiological, endocrine, and behavioral differences between gregarious and solitarious forms of the desert locust, Schistocerca gregaria (Forsk.) (Orthoptera, Acrididae), a constant supply of rather large numbers of solitary individuals has to be guaranteed. This represents a bottleneck, mainly because of the intensity of the labor involved and limited laboratory accommodation. The method we describe here substantially reduces the space and manpower needed. The survival rate we obtained in the solitarised population was relatively high, reaching about 55%. The optimal rearing temperature proved to be 32–36 °C. Cabbage leaves and oat flakes sufficed for feeding all year round. Special racks have been designed that enable high density stacking and easy handling. The solitarisation process was monitored over ten consecutive generations. Changes in morphometrics, eye stripes, color, and behavior were recorded, of which only morphometrics, temperature related development, and mortality are discussed. A shift towards the solitarious phase was recorded, with clear differences between gregarious, 1^st generation and 7^th to 10^th generation solitarious locusts.     

High‐throughput sequencing and graph‐based cluster analysis facilitate microsatellite development from a highly complex genome

Despite recent advances in high‐throughput sequencing, difficulties are often encountered when developing microsatellites for species with large and complex genomes. This probably reflects the close association in many species of microsatellites with cryptic repetitive elements. We therefore developed a novel approach for isolating polymorphic microsatellites from the club‐legged grasshopper (Gomphocerus sibiricus), an emerging quantitative genetic and behavioral model system. Whole genome shotgun Illumina MiSeq sequencing was used to generate over three million 300 bp paired‐end reads, of which 67.75% were grouped into 40,548 clusters within RepeatExplorer. Annotations of the top 468 clusters, which represent 60.5% of the reads, revealed homology to satellite DNA and a variety of transposable elements. Evaluating 96 primer pairs in eight wild‐caught individuals, we found that primers mined from singleton reads were six times more likely to amplify a single polymorphic microsatellite locus than primers mined from clusters. Our study provides experimental evidence in support of the notion that microsatellites associated with repetitive elements are less likely to successfully amplify. It also reveals how advances in high‐throughput sequencing and graph‐based repetitive DNA analysis can be leveraged to isolate polymorphic microsatellites from complex genomes.     

Direct and indirect genetic effects on reproductive investment in a grasshopper

A fundamental part of the quantitative genetic theory deals with the partitioning of the phenotypic variance into additive genetic and environmental components. During interaction with conspecifics, the interaction partner becomes a part of the environment from the perspective of the focal individual. If the interaction effects have a genetic basis, they are called indirect genetic effects (IGEs) and can evolve along with direct genetic effects. Sexual reproduction is a classic context where potential conflict between males and females can arise from trade‐offs between current and future investments. We studied five female fecundity traits, egg length and number, egg pod length and number and latency to first egg pod, and estimated the direct and IGEs using a half‐sib breeding design in the grasshopper Chorthippus biguttulus. We found that the male IGEs were an order of magnitude lower than the direct genetic effects and were not significantly different from zero. However, there was some indication that IGEs were larger shortly after mating, consistent with the idea that IGEs fade with time after interaction. Female direct heritabilities were moderate to low. Simulation shows that the variance component estimates can appear larger with less data, calling for care when interpreting variance components estimated with low power. Our results illustrate that the contribution of male IGEs is overall low on the phenotypic variance of female fecundity traits. Thus, even in the relevant context of sexual conflict, the influence of male IGEs on the evolutionary trajectory of female reproductive traits is likely to be small.