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.     

Perceptual,developmental, experiential,and physiological parameters of swimming in Melanopline grasshoppers (Orthoptera: Acrididae)

The roles of perception, development, experience, and physiology on the swimming behavior of grasshoppers in an arena were investigated usingMelanoplus bivittatus, M. differentialis, andM. sanguinipes. The parameters of swimming included capacity (the ability to reach the edge of a 45-cm-diameter water basin within 3 min), net displacement time (time required to reach the edge of the arena), and orientation (ability to make initial contact with a target pattern).Melanoplus sanguinipes adults were most attracted to a vertical rectangle set at 90° to the water surface (the standard target). Orientation ability decreased significantly as the target became square or it declined to 60°, and there was virtually no orientation to horizontal patterns or those at 45°. All nymphal instars ofM. sanguinipes exhibited the capacity to swim and orient to a standard target. Although the net displacement time was lowest from the third instar through the adult stages, the earlier instars (first through fourth) had the greatest relative net displacement rates. As adults aged, their net displacement time and orientation ability declined significantly, particularly in males. BothM. differentialis andM. sanguinipes adults showed a decline in net displacement time over a 10-day trial period. The loss of a hind leg did not significantly alter swimming performance of eitherM. bivittatus orM. sanguinipes adults, but this alteration significantly reduced the net displacement time ofM. differentialis. DecerebratedM. differentialis adults were capable of swimming for several minutes.     

Behavioral influences on food selection in grasshoppers (Orthoptera: Acrididae)

Host plant selectivity has been established for many species of grasshoppers but the mechanisms involved are not completely known. General undirected activity was enhanced by favorable temperature, humidity and illumination. Positive phototactic responses were elicited by directed illumination, color and visual patterns.Orientation to stimuli from food materials generally took place only after contact had been made with the mouthparts. Discrimination among various extracts and extract concentrations from different plant species was demonstrated.Individual grasshoppers in laboratory experiments with artificial diet arrays selected resting sites independent of food location. In some cases feeding was influenced by resting site location.The feeding behavior of grasshoppers will cause them to remain in areas of favorable host plants through a general type of orthokinesis.

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Zusammenfassung Wirtspflanzen-Wahlvermögen ist bei vielen Feldheuschrecken nachgewiesen worden. Jedoch werden die Eiablage-Orte im allgemeinen nicht mit Rücksicht auf die Verfügbarkeit von Wirtspflanzen für die schlüpfenden Larven gewählt. Diese müssen geeignete Wirtspflanzen unter vielen verfügbaren selbst aussuchen.Innerhalb optimaler Temperatur-und Feuchtigkeitsbereiche wird die allgemeine ungerichtete Aktivität durch genügende Helligkeit verstärkt. Es wurden positive phototaktische Reaktionen zu gerichtetem Licht nachgewiesen. Die Reaktion auf gerichtete Beleuchtung war zwischen 3600 und 4750Å am größten. Wellenlängen ober-und unterhalb davon ergaben geringere Reaktionen.Senkrechte Objekte oder Muster riefen positive Taxien hervor.Olfaktorische Anlockung war sehr begrenzt, aber sobald die Nahrung einmal mit den Mundwerkzeugen in Berührung gekommen war, waren die Heuschrecken sehr wählerisch. Bei verschiedenen Arten wurde die Fähigkeit nachgewiesen, zwischen einer ganzen Reihe von verschiedenen Pflanzenextrakten wählen zu können, die in eine künstliche Trägerdiät eingefügt waren. Unterscheidung zwischen geringen Konzentrationsunterschieden der extrahierten Substanzen war nachweisbar.Zeitraffer-Aufnahmen zeigten, daß die Extraktpräparate in der Reihenfolge ihrer Annehmbarkeit ausgewählt wurden. Gewöhnlich wurde der Fraß auf einige wenige Präparate beschränkt, bis sie völlig verzehrt waren. Erst dann wurden die anderen Präparate in der Reihenfolge ihrer Annehmlichkeit gefressen.Mit Zeitraffer-Aufnahmen wurde das Verhalten einzelner Heuschrecken verfolgt, die zusammen mit Serien von künstlichen Nahrungstabletten mit Pflanzenextrakten gekäfigt worden waren. Es zeigte sich, daß die Heuschrecken Ruheplätze wählen, von denen aus sie sich zum Fressen und Trinken bewegen. Bestimmte Bewegungsmuster waren ausgebildet. Die Lage der Ruheplätze wurde von den anwesenden Nahrungsstoffen nicht beeinflußt, aber in einigen Fällen das Fressen von der Nähe der Ruheplätze.Es wurde angenommen, daß visuelle Reize die Orientierung der Feldheuschrecken unterstützen, aber die Wirtspflanzenwahl findet erst nach Berührung mit den Mundwerkzeugen statt. Feldheuschrecken haben die Gewohnheit, Gebiete, die keine geeigneten Wirtspflanzen enthalten, zu durchqueren und sich auf solchen mit geeigneten Wirten mit Hilfe eines allgemeinen Typs von Orthokinese zu scharen. Da die anziehenderen Pflanzen gewöhnlich auch das größte biologische Potential bieten, werden Verteiling und Dichte der Heuschrecken von der Wirtspflanzenwahl beeinflußt.

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Published with the approval of the Director of the North Dakota Agricultural Experiment Station as journal Article No...... Contribution from North Central Regional Project NC-52.     

Thermoregulation in four species of British grasshoppers (Orthoptera: Acrididae)

1. This study examines the extent to which thermal balance and thermoregulatory ability may contribute to habitat partitioning in insect herbivores.
2. The distribution of four species of grasshopper on a Breckland grass heath is described. Myrmeleotettix maculatus is restricted to short swards, Omocestus viridulus is restricted to long swards, and Chorthippus brunneus and Stenobothrus lineatus are found on swards of intermediate length.
3. Short swards are warmer on average than long swards, but lack cooler refuges on hot days.
4. Chorthippus brunneus and O. viridulus are better able to raise their body temperatures at low ambient temperatures than M. maculatus and S. lineatus . Omocestus viridulus is less able to reduce body temperature at high ambient temperature.
5. Myrmeleotettix maculatus may be precluded from inhabiting cooler long swards because of its inability to raise body temperatures at low ambient temperatures. Omocestus viridulus may avoid short swards because of the danger of overheating.
6. Thermoregulatory ability is a good predictor of the distribution of the grasshoppers in swards of differing length and microclimate.     

Evolution of chromosome number in grasshoppers (Orthoptera: Caelifera: Acrididae)

Organisms Diversity & Evolution - Orthoptera have some of the largest genomes of all insects. At the same time, the architecture of their genomes remains poorly understood. Comparative...     

Feeding patterns in grasshoppers (Orthoptera: Acrididae): Factors influencing diet specialization

Summary Diets of grasshopper species from two arid grassland communities in Trans-Pecos, Texas, were determined by gut analysis. Species-specific food plant choice and niche breadths are presented for each of these species. As a group, grasshoppers range from monophagous to polyphagous feeders although most species fall in the oligophagous to polyphagous group. Phylogenetic constraints are evident such that gomphocerinae are primarily grass feeders while melanoplinae feed predominantly on forbs; the oedipodinae show less clearcut tendencies.Feeding patterns are remarkably constant from site to site and overall, community niche breadth distributions between sites do not differ greatly. Individual species tend to eat the same plant species at various sites and maintain similar niche breadths. Species with relatively specialized diets tend to feed on predictable plant species such as grasses and long-lived perrenial forbs.Grasshopper feeding patterns present some problems to the current theory of herbivore diet specialization since forb feeding melanoplines tend to be polyphagous (contrary to predictions). Life history patterns unrelated to tracking host plants may explain some aspects of diet breadth since diet selectivities are presumably adjusted according to the probability of finding suitable food plants.     

The influence of environmental factors on dormancy and duration of egg development in Metrioptera roeseli (Orthoptera: Tettigoniidae)

Summary Developing eggs of Metrioptera roeseli HGB. have an obligate embryonic diapause in stage 23 and a facultative initial diapause in stage 4. Initial diapause is lacking when the ovipositing females are kept at long day photoperiod (LD 16/8), but is induced at LD 14/10 and LD 8/16. When natural light conditions are given in the laboratory, the females mostly lay diapausing eggs from the end of August onwards. In eggs without initial diapause, a larger number of embryos reach a stage, in which the embryonic diapause can be broken by chilling, only at favorable temperature (4 weeks at 24°C or 8 at 18°C) and in contact with water before the first winter. Thus, some individuals of a given population of M. roeseli have an annual, others a biennial life cycle. The variability in the duration of egg development is due to a photoperiodically induced, facultative initial diapause and to a possible quiescence caused by insufficient temperature and/or moisture.     

Action windows for optimum control of rangeland grasshoppers (Orthoptera: Acrididae)

Different assemblages of primary and secondary pest grasshopper species were found in 5 different rangeland plant communities in western North Dakota. The action window for their control (i.e., the interval when control is likely to be efficacious) with short-lived insecticides can be visualized in terms of time, grasshopper phenology, or plant phenology. Action windows ranged from 14 d duration in habitats dominated by western wheatgrass to 38 d duration in habitats dominated by needle-and-thread or by crested wheatgrass. Action windows opened 11-15 d later in rhizominous grass habitats than in bunchgrass habitats because of increased presence of late-hatching secondary pest species. In all habitat types, action windows closed primarily in response to imminent oviposition by a ubiquitous primary pest species, Melanoplus sanguinipes (F.). In all habitat types, action windows tended to open during seed development of 2 common and conspicuous grasses, needle-and-thread and green needlegrass. No such consistent indicator for closure of action windows was detected.     

Male and female genitalia in some Libyan species of Acrididae (Orthoptera: Acridoidea)

A comparative study of male and female genitalia was carried out in thirty‐seven Libyan species representing twenty genera of the family Acrididae. An attempt has been made to describe and illustrate the different structures, namely, epiphallus, aedeagus, subgenital plate, supra‐anal plate and cerci of the male, and spermatheca, ovipositor, subgenital plate, supra‐anal plate and cerci of the female, in Acridids, with an aim to discover their significance in order to make the identification of genera and species, together with other generic characters, more perfect and convenient. Distinct family characters are shield or bridge‐shaped condition of epiphallus; presence or absence of dorso‐lateral appendices, oval sclerites and lophi on epiphallus; divided, undivided or flexured condition of aedeagus; presence or absence of gonopore process on aedeagus; condition of apical and pre‐apical diverticula of spermatheca; presence or absence of glandular pouches of Cornstock and Kellog on female subgenital plate; and rudimentary or well developed condition of egg‐guide. Stable characters for separating the subfamilies are taken to be presence or absence of ancorae on epiphallus, long or short condition of aedeagal sclerites; elongate, slender or short and broad condition of ovipositor valves: presence or absence of Jannone's organs and setae on posterior margin of female subgenital plate; and shape of diverticula of spermatheca. Useful generic characters are shape of male subgenital plate, supra‐anal plate and cerci, broad or narrow condition of bridge, presence or absence of branch of bridge connecting lophi with bridge of epiphallus; mono‐, bi‐ or tri‐lobate condition of lophi of epiphallus, length and upcurved or downcurved condition of apical valve of aedeagus, shape of posterior margin of female subgenital plate, presence of setae on the whole posterior margin or confined to lateral margins only; and toothed, tuberculate or smooth condition of ovipositor valves, length of the lateral apodeme in relation to the dorsal valves. Specific characters are shape of egg‐guide of female subgenital plate, shape of ovipositor valves and apical tips, shape of male supra‐anal plate and cerci, size of anterior and posterior lobes of lophi of epiphallus, size and shape of ancorae, shape of apical valves of aedeagus; and size of apical and pre‐apical diverticula and presence of protuberance on pre‐apical diverticulum.     

The complete mitochondrial genome of Gomphocerus tibetanus Uvarov, 1935 (Orthoptera: Acrididae: Gomphocerinae)

The complete nucleotide sequence of the mitochondrial genome (mitogenome) of Gomphocerus tibetanus Uvarov, 1935 (Orthoptera: Acrididae: Gomphocerinae) was determined. It is 15,571 bp in length and contains 74.8% A + T. All Gomphocerus tibetanus protein-coding sequences start with a typical ATN codon. The usual termination codons (TAA and TAG) were found from 13 PCGs except COI and COII which took incomplete codon T as termination codons. All tRNA genes could be folded into the typical cloverleaf secondary structure, except tRNA^Ser(AGN) lacking of dihydrouridine (D) arm. The sizes of the large and small ribosomal RNA genes are 1313 and 822 bp, respectively. The A + T content of the A + T-rich region is 82.3%. A preliminary analysis on characteristics of Gomphocerinae mitogenome was made by comparision among three Gomphocerinae mitogenomes and Locusta migratoria.     

Visual behaviors of the migratory grasshopper,Melanoplus sanguinipes F. (Orthoptera: Acrididae)

The visual behavior of adult Melanoplus sanguinipesF. (Orthoptera: Acrididae) was investigated by placing individuals in the center of an arena and recording their orientation responses to visual targets at the perimeter of the arena. Targets that reflected more 540- to 570-nm light were approached more frequently; however, when reflectance in the 540 -to 570-nm region was combined with reflectance in the 400- to 520-nm region, orientation responses were reduced significantly. This suggests that spectral discrimination in M. sanguinipesinvolves at least two classes of photoreceptors, which respond to different regions of the wavelength spectrum. In addition, grasshoppers oriented to vertical, but not horizontal, contrasting stripes. However, when vertical stripes were added to targets reflecting 520- to 650-nm light, responses to verticals on these targets were not enhanced relative to verticals presented against a target background of 400- to 520-nm + 520- to 650-nm light. Thus, spectral discrimination and vertical stripe fixation appear to be two distinct visual behaviors, controlled by outputs from two classes of photoreceptors and a single class of photoreceptors, respectively, and may be used in different physiological or ecological contexts.     

Variation in dietary patterns among and within polyphagous grasshopper species (Orthoptera: Acrididae)

Individuals of two polyphagous grasshopper species,Melanoplus differentialis andSchistocerca albolineata, were reared under standardized conditions to eliminate prior experience as an influence on feeding behavior. Individuals were offered four plants in simultaneous choice tests from 8 to 14 times during development to adulthood. Individual insects varied in the preferred plant and the strength of preference, in the strength of the preference hierarchy among the four plants, and in breadth of feeding in choice tests. Average feeding diversity in choice tests increased significantly in later instars, but the sexes did not differ in feeding pattern. In both species a significant preference for one plant was generally but not invariably associated with a consistent preference hierarchy. Breadth of feeding in all tests was inversely related to the strength of preference and of the preference hierarchy. Although the two species differed in feeding diversity and in the relationship between preference and strength of preference hierarchy, evidence suggests that these differences were due to the specific plants used rather than to true interspecific differences. The existence of such variation under highly standardized rearing conditions suggests that genetic variation for these characteristics may exist in natural populations of polyphagous grasshoppers.     

The influence of proline on diet selection: sex-specific feeding preferences by the grasshoppers Ageneotettix deorum and Phoetaliotes nebrascensis (Orthoptera: Acrididae)

Diet selection based on the level of proline in an insect's host plant has been observed for a number of phytophagous insects, but few studies have examined potential differences in feeding preferences between males and females. The level of proline among an insect's host plants, particularly in drought-stressed plants, can be highly variable and often is positively correlated with soluble nitrogen levels. Additionally, proline is known to participate in a number of physiological functions in insects. We tested the effect of proline as a feeding stimulant in reproductively active grasshoppers using the graminivorous Ageneotettix deorum and the generalist, but mostly graminivorous, Phoetaliotes nebrascensis. Feeding preference tests using diets with representative free amino acid and sucrose levels but varying proline levels (zero, normal and 3 x normal) were examined. The feeding preference exhibited by both species was sex-specific, although the sex-specific response was more pronounced in P. nebrascensis than in A. deorum. Females of both species displayed preferences for diets high in proline. Males of neither species exhibited a preference for proline when responses were averaged over all treatment levels. However, within specific treatment combinations, male A. deorum preferred diets with high proline over diets with zero proline. These results suggest that diet selection for specific nutrients may vary between males and females because of differences in their physiological status and, possibly, differences in the nutritional requirements associated with reproduction. These results also suggest that subtle shifts in the concentration of individual nutrients within an insect's host plant may greatly influence insect feeding patterns.     

Insecticidal activity of photoactive dyes to American and migratory grasshoppers (Orthoptera: Acrididae)

Many photoactive dyes are relatively nontoxic to vertebrates despite their insecticidal properties. Several photoactive dyes known to be toxic to some groups of insects were evaluated at various concentrations for toxicity to American and migratory grasshoppers in laboratory and field studies. Rose bengal and phloxine B were effective at inducing mortality of grasshoppers when applied at 2 and 5% to bran bait, though erythrosin B and uranine were ineffective. Partial replacement of phloxine with uranine in dye mixtures resulted in no significant loss of efficacy. Some indication of feeding inhibition was observed at high dye concentrations, so minimum effective dosages, probably 2%, are optimal. Phloxine B and rose bengal appeared to be stable upon exposure to sunlight, and able to withstand at least 24 h of sunlight without significant degradation. Dyes such as phloxine B could be a viable grasshopper control agent for small or medium-sized grasshopper species because mortality can be induced by consumption of a single flake dusted with 5% dye, and yet pose little hazard to vertebrates. Large species such as American grasshopper must consume several flakes before mortality is induced.     

Antennal sensilla of grasshoppers (Orthoptera: Acrididae) in relation to food preferences and habits

The external structure, i.e. number and distribution of sensillae on male and female antennae of 12 species of grasshoppers belonging to Pamphaginae, Catantopinae, Oedipodinae and Gomphocerinae in the grasslands of Inner Mongolia was investigated using scanning electron microscopy. Five major types of antennal sensillae were detected - trichoid, long basiconic, short basiconic, slender and short basiconic, and coeloconic sensillae. Total number of antennal sensillae varied among different sexes, subfamilies, feeding groups, life forms and eco-forms. Males showed significantly more sensillae than females, due to presence of more short basiconic and coeloconic sensillae. Species under Catantopinae showed more long basiconic sensillae than the others. The Oedipodinae had the highest number of slender and short basiconic sensillae and coeloconic sensillae, followed by Catantopinae and Gomphocerinae; while Pamphaginae had the fewest. The total number of sensillae showed the same trend for these two types amongst the subfamilies as well, species which prefer habits on the ground possessed fewer antennal sensillae than species which prefer to stay on plants. The maximal number of antennal sensillae were observed in hygrophytous species,Chorthippus albomarginatus, in the 12 grasshopper species investigated, although the data is not statistically significant. The general trend which emerged was that species feeding on grass possessed more antennal sensillae, particularly coeloconic sensillae, compared to other feeding group species.     

Genotype–environment interaction and the ontogeny of diet-induced phenotypic plasticity in size and shape of Melanoplus femurrubrum (Orthoptera: Acrididae)

The developmental origin of phenotypic plasticity in morphological shape can be attributed to environment-specific changes in growth of overall body size, localized growth of a morphological structure or a combination of both. I monitored morphological development in the first four nymphal instars of grasshoppers (Melanoplus femurrubrum) raised on two different plant diets to determine the ontogenetic origins of diet-induced phenotypic plasticity and to quantify genetic variation for phenotypic plasticity. I measured diet-induced phenotypic plasticity in body size (tibia length), head size (articular width and mandible depth) and head shape (residual articular width and residual mandible depth) for grasshoppers from 37 full-sib families raised on either a hard plant diet (Lolium perenne) or a soft plant diet (Trifolium repens). By the second to third nymphal instar, grasshoppers raised on a hard plant diet had significantly smaller mean tibia length and greater mean residual articular width (distance between mandibles adjusted for body size) compared with full-sibs raised on a soft plant diet. However, there was no significant phenotypic plasticity in mean unadjusted articular width and mandible depth, and in mean residual mandible depth. At the population level, development of diet-induced phenotypic plasticity in grasshopper head shape is mediated by plastic changes in allocation to tissue growth that maintain growth of head size on hard, low-nutrient diets while reducing growth of body size. Within the population, there was substantial variation in the plasticity of growth trajectories since different full-sib families developed phenotypic plasticity of residual articular width through different combinations of head and body size growth. Genetic variation for diet-induced phenotypic plasticity of residual articular width, residual mandible depth and tibia length, as estimated by genotype–environment interaction, exhibited significant fluctuation through ontogeny (repeated measures MANOVA , family × plant × instar, P < 0.01). For example, there was significant genetic variation for phenotypic plasticity of residual articular width in the third nymphal instar, but not earlier or later in ontogeny. The observed patterns of genetic variation are discussed with reference to short-term constraints and the evolution of phenotypic plasticity.