Accessory glands of male reproductive system in Pseudochorthippus parallelus parallelus (Zetterstedt, 1821) (Orthoptera: Acrididae): A light and electron microscopic study.

The accessory glands of male reproductive system in insects play a significant role in the reproduction process by protecting sperm in spermatheca, preventing female to accept other males after mating and stimulating oviposition. The number, structure, and arrangement of the tubules of accessory glands can change from species to species. In this study, the accessory glands belonging the male reproductive system in Pseudochorthippus parallelus parallelus (Zetterstedt, 1821) (Orthoptera, Acrididae) were examined with stereomicroscope, light microscope, scanning (SEM), and transmission (TEM) electron microscopes at Gazi University, Faculty of Science in 2017-2019. P. parallelus parallelus is a widespread species that is located at the extending areas from Italy to the Northern Europe and also in Turkey. The accessory glands of P. parallelus parallelus' male reproductive system are composed of about 10 tubules. The tubules can be classified into two groups according to the thickness of their muscle tissues. Both groups have single layered epithelial cells with mitochondria, well-developed endoplasmic reticulum, spherical nucleus with electron dense chromatin, secretory vesicles and multivesicular bodies in their cytoplasm. In addition, apocrine type secretion is seen in epithelial cells.

Revealing hidden density-dependent phenotypic plasticity in sedentary grasshoppers in the genus Schistocerca Stål (Orthoptera: Acrididae: Cyrtacanthacridinae).

Comparative quantification of reaction norms across closely related species in a clade is rare, but such a study can reveal valuable insights into understanding how reaction norms evolve along phylogeny. The grasshopper genus Schistocerca Stål (Orthoptera: Acrididae: Cyrtacanthacridinae) is an ideal group to study the evolution of density-dependent phenotypic plasticity because it includes both swarming locusts and non-swarming sedentary grasshoppers, which show varying degrees of plastic reaction norms in many traits. The swarming locusts exhibit locust phase polyphenism in which cryptically colored and solitary individuals can transform into conspicuously colored and highly gregarious individuals in response to increases in population density. The sedentary grasshoppers do not swarm in nature, and thus it has been assumed that they have little or no expression of plastic reaction norms in many traits, except for color, which has been shown to be a phylogenetically conserved trait. In this study, we have quantified density-dependent reaction norms in behavior, color, body size, and morphometric ratio in the nymphs of four sedentary species within Schistocerca by conducting explicit rearing experiments to induce potential phenotypic changes in response to isolation and crowding. In contrast to our previous assumption, we find that all four species show a certain level of density-dependent plastic reaction norms, which implies that these sedentary species have hidden reaction norms that can only be induced experimentally, some components of which must be phylogenetically conserved. Furthermore, we demonstrate that rearing density differentially affects the expression of reaction norms in different species, suggesting that different reaction norms must have followed independent evolutionary trajectories.

Integrating genomic and phenotypic data to evaluate alternative phylogenetic and species delimitation hypotheses in a recent evolutionary radiation of grasshoppers.

Although resolving phylogenetic relationships and establishing species limits are primary goals of systematics, these tasks remain challenging at both conceptual and analytical levels. Here, we integrated genomic and phenotypic data and employed a comprehensive suite of coalescent-based analyses to develop and evaluate competing phylogenetic and species delimitation hypotheses in a recent evolutionary radiation of grasshoppers (Chorthippus binotatus group) composed of two species and eight putative subspecies. To resolve the evolutionary relationships within this complex, we first evaluated alternative phylogenetic hypotheses arising from multiple schemes of genomic data processing and contrasted genetic-based inferences with different sources of phenotypic information. Second, we examined the importance of number of loci, demographic priors, number and kind of phenotypic characters and sex-based trait variation for developing alternative species delimitation hypotheses. The best-supported topology was largely compatible with phenotypic data and showed the presence of two clades corresponding to the nominative species groups, one including three well-resolved lineages and the other comprising a four-lineage polytomy and a well-differentiated sister taxon. Integrative species delimitation analyses indicated that the number of employed loci had little impact on the obtained inferences but revealed the higher power provided by an increasing number of phenotypic characters and the usefulness of assessing their phylogenetic information content and differences between sexes in among-taxa trait variation. Overall, our study highlights the importance of integrating multiple sources of information to test competing phylogenetic hypotheses and elucidate the evolutionary history of species complexes representing early stages of divergence where conflicting inferences are more prone to appear.

Two types of albino mutants in desert and migratory locusts are caused by gene defects in the same signaling pathway.

Albinism is caused by mutations in the genes involved in melanin production. Albino nymphs of Locusta migratoria and Schistocerca gregaria reared under crowded conditions are uniformly creamy-white in color. However, nothing is known about the molecular mechanisms underlying this phenomenon in locusts. The albino strain of L. migratoria is known to lack the dark-color-inducing neuropeptide corazonin (Crz). In this study, we report that this albino strain has a 10-base-pair deletion in the gene LmCRZ, which encodes Crz. This mutation was found to cause a frame-shift, resulting in a null mutation in Crz. On the other hand, the albino strain of S. gregaria is known to have an intact Crz. This strain was found to possess a single-nucleotide substitution in the middle of the Crz receptor-encoding gene, SgCRZR, which caused a nonsense mutation, resulting in a truncated receptor. Silencing of SgCRZR in wild-type S. gregaria nymphs greatly reduced the area and intensity of their black patterning, suggesting that the functional defect of SgCRZR likely causes the albinism. The expression level of SgCRZR in the albino S. gregaria was comparable to that in the wild type. Unlike the wild type, the albino strain of this locust did not show a phase-dependent shift in a morphometric trait controlled by Crz. From these results, we conclude that the mutations in LmCRZ and SgCRZR are responsible for the albinism in L. migratoria and S. gregaria, respectively, indicating that the two types of albinism are caused by different genetic defects in the same Crz signaling pathway.

Biomechanical Factors in the Adaptations of Insect Tibia Cuticle.

Insects are among the most diverse groups of animals on Earth. Their cuticle exoskeletons vary greatly in terms of size and shape, and are subjected to different applied forces during daily activities. We investigated the biomechanics of the tibiae of three different insect species: the desert locust (Schistocerca gregaria), American cockroach (Periplaneta americana) and Death's Head cockroach (Blaberus discoidalis). In a previous work, we showed that these tibiae vary not only in geometry (length, radius and thickness) but also in material quality (Young's modulus) and in the applied stress required to cause failure when loaded in bending. In the present work we used kinematic data from the literature to estimate the forces and stresses arising in vivo for various different activities, and thus calculated factors of safety defined as the ratio between the failure stress and the in vivo stress, adjusting the failure stress to a lower value to allow for fatigue failure in the case of frequently repeated activities. Factors of safety were found to vary considerably, being as little as 1.7 for the most strenuous activities, such as jumping or escaping from tight spaces. Our results show that these limbs have evolved to the point where they are close to optimal, and that instantaneous failure during high-stress activities is more critical than long-term fatigue failure. This work contributes to the discussion on how form and material properties have evolved in response to the mechanical functions of the same body part in different insects.

The closed spiracle phase of discontinuous gas exchange predicts diving duration in the grasshopper Paracinema tricolor.

The discontinuous gas exchange (DGE) pattern of respiration shown by many arthropods includes periods of spiracle closure (C-phase) and is largely thought to serve as a physiological adaptation to restrict water loss in terrestrial environments. One major challenge to this hypothesis is to explain the presence of DGE in insects in moist environments. Here, we show a novel ecological correlate of the C-phase, namely, diving behaviour in mesic Paracinema tricolor grasshoppers. Notably, maximal dive duration is positively correlated with C-phase length, even after accounting for mass scaling and absolute metabolic rate. Here, we propose that an additional advantage of DGE may be conferred by allowing the tracheal system to act as a sealed underwater oxygen reservoir. Spiracle closure may facilitate underwater submersion, which, in turn, may contribute to predator avoidance, the survival of accidental immersion or periodic flooding and the exploitation of underwater resources.

Knockdown of the corazonin gene reveals its critical role in the control of gregarious characteristics in the desert locust.

The two plague locusts, Schistocerca gregaria and Locusta migratoria, exhibit density-dependent phase polyphenism. Nymphs occurring at low population densities (solitarious forms) are uniformly colored and match their body color to the background color of their habitat, whereas those occurring at high population densities (gregarious) develop black patterns. An injection of the neuropeptide, corazonin (Crz) has been shown to induce black patterns in locusts and affect the classical morphometric ratio, F/C (F, hind femur length; C, maximum head width). We herein identified and cloned the CRZ genes from S. gregaria (SgCRZ) and L. migratoria. A comparative analysis of prepro-Crz sequences among insects showed that the functional peptide was well conserved; its conservation was limited to the peptide region. Silencing of the identified SgCRZ gene in gregarious S. gregaria nymphs markedly lightened their body color and shifted the adult F/C ratio toward the value typical of solitarious forms. In addition, knockdown of the gene in solitarious nymphs strongly inhibited darkening even after a transfer to crowded conditions; however, these individuals developed black patterns after being injected with the Crz as a rescue treatment. SgCRZ was constitutively expressed in the brains of S. gregaria during nymphal development in both phases. This gene was highly expressed not only in the brain in both phases, but also in the corpora allata in the gregarious phase. This conspicuous phase-dependent difference in SgCRZ gene expression may indicate a functional role in the control of phase polyphenism in this locust.

On cockroaches of the subfamily Epilamprinae (Dictyoptera: Blaberidae) from South India and Sri Lanka, with descriptions of new taxa.

The new genus Indoapterolampra, gen. nov. and two new species (I. rugosiuscula sp. nov. and Morphna lucida sp. nov.) are described. Rhabdoblatta praecipua (Walker, 1868) is removed from the synonymy with 'Polyzosteria' terranea Walker, 1868. The latter species is considered Epilamprinae gen. sp. The lectotype of Phoraspis (Thorax) porcellana Saussure, 1862 is designated. A key for the genera of Epilamprinae from South India and Sri Lanka is provided. Detailed morphological descriptions of the studied taxa are given. The structure of the male genitalia of I. rugosiuscula sp. nov., M. lucida sp. nov., M. plana (Brunner von Wattenwyl, 1865), M. decolyi (Bolivar, 1897) and R. praecipua and that of the female genital complex of M. decolyi, P. (T.) porcellana and Phlebonotus anomalus (Saussure, 1863) are described for the first time. Some aspects of the cockroach evolution are briefly discussed. 

Morphometry of Cornops aquaticum (Orthoptera: Acrididae: Leptysminae) in the Pantanal of Mato Grosso, Brazil / Morfometria de Cornops aquaticum (Orthoptera: Acrididae: Leptysminae) no Pantanal de Mato Grosso, Brasil

Insects show morphometric variations associated with the environment that may be the result of phenotypic response or genetic inheritance, or both. Thereby, studies that emphasise the variability in body size are very useful for understanding the dynamics and the stability of ecological systems. Cornops aquaticum (Bruner, 1906) (Acrididae) is a semi-aquatic grasshopper, distributed from the southeast of Mexico to the south of Buenos Aires Province, Argentina, and is intimately associated with the aquatic macrophytes Eichhornia spp. and Pontederia spp. In its wide habitat distribution, C. aquaticum shows variations in its life cycle and morphometric differences that were observed suggesting geographic and host plant influence. Considering these findings, this study aimed to find out the morphometric characteristics of this species at the Pantanal of Poconé – MT, using the protocol of the project “HICWA – Host-Insect Coevolution on Waterhyacinth”, as well as to assess possible differences in each stage of development between the sexes and among seasonal periods (flood, high water, low water and dry). During 12 months a total of 600 individuals were collected in monthly collections of 50 grasshoppers, and of this total, 261 were adults and 339 nymphs. The following measurements were taken: total length (A); body length (B); wing length (I) and measurement of the hind femur (H). The results showed that both male and female have different measurements but not correlated with seasonal periods. The average obtained for each character and the seasonality showed the highest values during the flood period. In nymphs, the measurement of the posterior femur presented the lower variation between individuals and characters.

Insetos apresentam variações morfométricas associadas ao ambiente que podem ser resultado tanto de respostas fenotípicas, quanto da herança genética, ou de ambos. Assim, estudos que enfatizam a variabilidade no tamanho do corpo do inseto são de grande utilidade para o entendimento da dinâmica e da estabilidade dos sistemas ecológicos. Cornops aquaticum (Bruner, 1906) (Acrididae) é um gafanhoto semi-aquático, distribuído desde o sudeste do México até o sul da província de Buenos Aires, Argentina, demonstrando íntima associação com macrófitas aquáticas dos gêneros Eichhornia e Pontederia. Em sua ampla distribuição de habitats, C. aquaticum apresenta variações em seu ciclo biológico e diferenças morfométricas que sugerem uma influência tanto geográfica, quanto da planta hospedeira. Diante disto, esse estudo objetivou conhecer as características morfométricas dessa espécie no Pantanal de Poconé (MT), empregando o protocolo do projeto “HICWA – Host-Insect Coevolution on Waterhyacinth”, bem como avaliar possíveis diferenças em cada estádio de desenvolvimento entre os sexos e entre os períodos sazonais dessa região (enchente, cheia, vazante e seca). Durante 12 meses foram coletados, mensalmente, 50 gafanhotos, totalizando 600 indivíduos, sendo 261 adultos e 339 ninfas, nos quais foram tomadas as medidas do comprimento total (A); comprimento do corpo (B); comprimento da asa (I) e medida do fêmur posterior (H). Os resultados indicam indivíduos adultos, tanto machos quanto fêmeas, de tamanho variado em todos os períodos sazonais, entretanto, essas variações não estão correlacionadas à sazonalidade. As médias obtidas para cada caracter entre os períodos sazonais demonstraram que houve diferenciação entre as medidas, revelando os maiores valores médios durante a enchente. Em ninfas, a menor variação entre os indivíduos em relação aos outros caracteres avaliados foi encontrada na medida do fêmur posterior.

Lack of correlation between vertical distribution and carrier frequency, and preference for open spaces in arboreal katydids that use extreme ultrasound, in Gorgona, Colombia (Orthoptera: Tettigoniidae) / Falta de correlación entre distribución vertical y frecuencia portadora, y preferencia por espacios abiertos en saltamontes arbóreos que utilizan ultrasonido extremo, en Gorgona, Colombia (Orthoptera: Tettigoniidae)

Male Tettigoniidae emit sound to attract conspecific females. The sound is produced by stridulation. During stridulation the forewings open and close, but it is during the closing stroke that the scraper contacts the file teeth to generate the predominant sound components, which are amplified by adjacent wing cells specialized in sound radiation. The sounds usually exceed the sonic boundary and might occur above 40 kHz, reaching extreme ultrasonic frequencies of 150kHz in some species. Here we test the hypothesis that Tettigoniidae species should prefer microhabitats that favour efficient signal transmission, i.e. that there is a relationship of sound frequency with the vertical distribution of the species (from ground to canopy) at Gorgona National Natural Park, Colombia. We sampled 16 trees and four different altitudinal levels between 1 and 20m above the understory vegetation. We placed collecting blankets separated by vertical distances of 5m, and knocked insects down using the technique known as fogging. We found no correlation between vertical distribution and carrier frequency, but there was a preference for open spaces (below the canopy and above the understory) in species using extreme ultrasound. This is the first quantitative description of the vertical distribution in neotropical species of the family Tettigoniidae and its relationship to the calling song frequency. Rev. Biol. Trop. 62 (Suppl. 1): 289-296. Epub 2014 February 01.

Los machos de Tettigoniidae producen sonido frotando las alas anteriores para atraer a sus hembras coespecíficas con fines reproductivos (mecanismo conocido como estridulación). Un borde esclerotizado (o raspador) en el ala derecha es frotado sobre una vena modificada con dientecillos en el ala izquierda. Durante la estridulación las alas abren y cierran, pero es durante el cierre que el raspador contacta los dientecillos de la lima y produce vibraciones que son amplificadas por celdas adyacentes especializadas para radiar sonido. Sonidos que superen los 20 000Hz, se consideran ultrasónicos, en los Tettigoniidae, la mayoría de los cantos superan el umbral sónico y pueden ocurrir a más de 40 000Hz, con casos extremos de hasta 148 000Hz. La esencia de este trabajo es el estudio de esta gama espectacular de frecuencias de la familia Tettigoniidae y su relación con la distribución vertical de los individuos en las especies que habitan en Gorgona. Se muestrearon 16 árboles a cuatro niveles diferentes de altitud entre 1 y ~20m sobre el sotobosque, instalando sabanas colectoras a intervalos de 4-5m. Los insectos se colectaron mediante el método de nebulización térmica. El análisis indica que no hay correlación entre la distribución vertical de las especies y la frecuencia del canto. Sin embargo se observó una preferencia por espacios abiertos en especies que cantan a frecuencias extremas. Este estudio representa la primera descripción cuantitativa de la distribución vertical de Tettigoniidae Neotropicales y su relación con la frecuencia del canto.

Non-swarming grasshoppers exhibit density-dependent phenotypic plasticity reminiscent of swarming locusts.

Locusts are well known for exhibiting an extreme form of density-dependent phenotypic plasticity known as locust phase polyphenism. At low density, locust nymphs are cryptically colored and shy, but at high density they transform into conspicuously colored and gregarious individuals. Most of what we know about locust phase polyphenism come from the study of the desert locust Schistocerca gregaria (Forskål), which is a devastating pest species affecting many countries in North Africa and the Middle East. The desert locust belongs to the grasshopper genus Schistocerca Stål, which includes mostly non-swarming, sedentary species. Recent phylogenetic studies suggest that the desert locust is the earliest branching lineage within Schistocerca, which raises a possibility that the presence of density-dependent phenotypic plasticity may be a plesiomorphic trait for the whole genus. In order to test this idea, we have quantified the effect of rearing density in terms of the resulting behavior, color, and morphology in two non-swarming Schistocerca species native to Florida. When reared in both isolated and crowded conditions, the two non-swarming species, Schistocerca americana (Drury) and Schistocerca serialis cubense (Saussure) clearly exhibited plastic reaction norms in all traits measured, which were reminiscent of the desert locust. Specifically, we found that both species were more active and more attracted to each other when reared in a crowded condition than in isolation. They were mainly bright green in color when isolated, but developed strong black patterns and conspicuous background colors when crowded. We found a strong effect of rearing density in terms of size. There were also more mechanoreceptor hairs on the outer face of the hind femora in the crowded nymphs in both species. Although both species responded similarly, there were some clear species-specific differences in terms of color and behavior. Furthermore, we compare and contrast our findings with those on the desert locust and other relevant studies. We attribute the presence of density-dependent phenotypic plasticity in the non-swarming Schistocerca species to phylogenetic conservatism, but there may be a possible role of local adaptation in further shaping the ultimate expressions of plasticity.

Dietary diversification and variations in the number of labrum sensilla in grasshoppers: which came first?

The diversity of the diet of grasshoppers (Acrididae, Orthoptera) is related to multiple factors, including the chemoreceptors on the antennae, palps and on the epipharyngeal face of the labrum. In the present study, we sought to understand the nature of the diet of 12 Moroccan acridian species and to try to relate various aspects of their diet to the number of labrum sensilla. If the effect of the labrum size on the number of sensilla is removed, four groups of species are recorded: (i) polyphagous species with a broad diet and numerous sensilla; (ii) polyphagous species with a graminivorous diet and numerous sensilla; (iii) oligophagous species feeding exclusively on Poaceae and with a medium number of sensilla; and (iv) strictly monophagous species feeding on a single plant species and with the smallest number of sensilla. These observations show the close relationship between the diet and the number of labrum sensilla. However, Sphingonotus rubescens, a polyphagous species, is an exception to this trend as it harbours a medium number of sensilla. We propose that the modification in the number of labrum sensilla is a result of a progressive adaptation to a different diet and does not represent its cause.

El comportamiento acústico de Fenestra bohlsii Giglio-Tos (Orthoptera: Acrididae: Gomphocerinae) / Acoustic behavior of Fenestra bohlsii Giglio-Tos (Orthoptera: Acrididae: Gomphocerinae)

The acoustic behavior of Fenestra bohlsii Giglio-Tos is described for the first time. The sounds and behaviors were observed and registered in captivity. The signals were digitized with the Sound-Blaster AWE64 Gold program and analysed with the Avisoft SAS Lab Pro 30 PC for MS Windows software. Seven different types of sounds are described as produced by males: spontaneous song (also used during the courtship), two different types of courtship song, assault song, tapping associated to the courtship, interaction between males and fly crackling. For each one, the characteristic oscillograms and frequency spectra are given. Sounds are produced by different mechanisms: femoro-tegminal stridulation, typical for Gomphocerinae, fly crackling, hind tarsi tapping and alar beat, the last produced by the beat and clash of hind alae, that is, the castanet method which up to now was only known, among Orthoptera, in Stenobothrus rubicundulus Kruseman & Jeekel. A description of the stridulatory file of male and female is given, as well as that of the alar special structures. Behavioral units and their sequence during the courtship are defined. There, in addition to the acoustic signals, visual signals are present, referring to positions, hind legs, antennae and palpi movements and body vibrations.

Are color or high rearing density related to migratory polyphenism in the band-winged grasshopper, Oedaleus asiaticus?

Locusts represent an impressive example of migratory polyphenism, with high densities triggering a switch from a solitarious, shorter dispersal range, and sometimes greenish phenotype to a gregarious and sometimes darker form exhibiting behavioral, morphological and physiological traits associated with long-distance migratory swarms. While such polyphenism has been well documented in Locusta migratoria and Schistocerca gregaria, the extent to which other grasshoppers exhibit this type of migratory polyphenism is unclear. Anecdotally, the Chinese grasshopper, Oedaleus asiaticus, forms migratory swarms comprised mostly of a darker, brown-colored morph, but also exhibits a non-migratory green-colored morph that predominates at low densities. In a population in Inner Mongolia not currently exhibiting migratory swarms, we found that while green and brown O. asiaticus are found concurrently across our sampled range, only brown grasshoppers were found in high densities. Differences between field-collected brown and green forms matched some but not key predictions associated with the hypothesis that the brown form is morphologically and physiologically specialized for gregarious migration. Controlling for body mass, brown forms had more massive thoraxes, abdomens and legs, and higher metabolic rates, but not more flight muscle or lipid stores. Further, the brown and green grasshoppers did not differ in gregarious behavior, and neither would fly in multiple lab and field trials. Lab or field-rearing at high densities for one-to-multiple juvenile instars caused grasshoppers to exhibit some morphological traits predicted to benefit migration (larger wings and a shift in relative mass from abdomen to thorax), but did not change color or induce flight behavior. One hypothesis to explain these data is that a migratory form of O. asiaticus is partially triggered by high field densities, but that existing ecological conditions blocked full expression of such traits (and outbreak swarms). Alternatively, color variation in this species may more tightly linked to other functions in this species such as crypsis or disease resistance, and mechanisms other than late-juvenile rearing density (e.g. genetic variation, maternal effects) may be more critical for promoting variation in color and/or migratory polyphenism.

Why certain male grasshoppers have clubbed antennae?

The significance of clubbed antennae in grasshoppers was assessed by investigating the sensilla repertoire of 15 gomphocerine species. The influence of the diet type (graminivorous or polyphagous) and the apical thickening of antenna on the number of sensilla were tested. It appears that the antennal thickening has a stronger impact on the number of sensilla than the food mode. The species bearing clubbed antennae are globally low in olfactive and contact sensilla, maybe in relation with a more complex courtship, but are richer in mechanoreceptors, probably involved in the control of antenna movements. The food mode change from oligophagy to polyphagy is not associated to an increase in the number of olfactive or contact sensilla. In contrast, the high number of these sensilla in a monophagous grasshopper feeding on Ulex bushes is interpreted in the context of alkaloid detection.

Endocrinology of reproduction and phase transition in locusts.

In the last decade, important progress has been made in the experimental analysis of the endocrine mechanisms controlling reproduction and phase transition in locusts. Phase transition is a very fascinating, but complex, phenomenon of phenotypic plasticity that is triggered by changes in population density and can lead to the formation of extremely devastating hopper bands and adult gregarious locust swarms. While some phase characteristics change within hours, others appear more gradually in the next stage(s), or even in the next generation(s). In adults, the phase status also has a major influence on the process of reproduction. A better understanding of how solitarious locusts become gregarious and how this switch affects reproductive physiology may result in novel strategies to fight locust plagues. In this paper, we will review the current knowledge concerning this close interaction between locust phase polyphenism and reproduction.

A test of Allen's rule in ectotherms: the case of two south American Melanopline Grasshoppers (Orthoptera: Acrididae) with partially overlapping geographic ranges / Un test de la regla de Allen en ectotermos: el caso de dos Saltamontes Melanoplinos (Orthoptera: Acrididae) sudamericanos con distribuciones Geográficas parcialmente solapadas

We studied the geographic variation of three morphometric characters in relation to body size in two South American grasshoppers (Acrididae), Dichroplus vittatus Bruner and D. pratensis Bruner to test Allen's rule in these ectotherms. Since both species follow the converse to Bergmann's rule owing to latitudinal and/or altitudinal variation in time available for growth and reproduction, geographic variation in body size proportions of protruding parts may obey to differential allometric growth in different geographic areas. Alternatively, it could reflect true Allenian variation related to thermoregulation. Body proportions were studied by correlation/regression analyses with geographic and climatic variables. In D. pratensis, body proportions increased with latitude and decreased with altitude. These results probably obey to the effects of water balance and seasonality on final body size, and on the allometric growth of the three studied characters not being related to thermoregulation. In D. vittatus, a generally non-significant trend towards the decrease of the mean proportions of all three characters with increasing latitude was observed. Nevertheless, also in this species, it is probable that the environmental gradient responds to seasonality factors (although not to water balance) that affect the length of growing season and, in consequence, body size and its allometric relationships. We conclude that the regularities in the geographic distribution of body proportions of D. pratensis and D. vittatus do not follow Allen's rule in the sense of thermoregulation, and result from variables that determine growing season length and the allometric growth of different body parts.

Estudiamos la variación geográfica de tres caracteres morfométricos en relación al tamaño corporal, en dos saltamontes sudamericanos (Acrididae), Dichroplus vittatus Bruner y D. pratensis Bruner, para verificar la regla de Allen en ectotermos. Ambas especies siguen la regla de Bergmann inversa por variación latitudinal y/o altitudinal en el tiempo disponible para crecimiento y reproducción; entonces la variación de proporciones de partes salientes del cuerpo, obedecería a crecimiento alométrico diferencial en diferentes áreas geográficas. Alternativamente, podría reflejar variación alleniana relacionada a termorregulación. Las proporciones corporales se estudiaron por análisis de correlación/regresión con variables geográficas y climáticas. En D. pratensis, las proporciones corporales aumentaron con la latitud, y decrecieron con la altitud. Esto probablemente obedezca a efectos del balance hídrico y la estacionalidad sobre el tamaño corporal final, y al crecimiento alométrico de los tres caracteres independientemente de la termorregulación. En D. vittatus, se observó una tendencia generalmente no significativa al decrecimiento de las proporciones de los tres caracteres con el incremento de latitud. Sin embargo, también es probable que el gradiente ambiental responda a factores de estacionalidad que afectan la duración de la estación de crecimiento y, consecuentemente, el tamaño corporal y sus relaciones alométricas. Concluimos qué las relaciones alométricas en la distribución geográfica de proporciones corporales de D. pratensis y D. vittatus no siguen la regla de Allen en el sentido de la termorregulación, y son el resultado de variables que determinan la duración de la estación de crecimiento y el crecimiento alométrico de diferentes partes del cuerpo.

Demographic study of two population outbreaks of Elasmoderus wagenknechti (Liebermann) (Orthoptera: Tristiridae) in the transitional desert of Chile

Under certain environmental conditions, several species of grasshoppers inhabiting rangeland areas (e.g., inter-valleys) of the Chilean transitional desert can irrupt demographically. One of them is Elasmoderus wagenknechti (Liebermann), an endemic species. We studied two outbreaks occurred in 1996 and 1999. The objectives of the research were to (i) estimate some demographic parameters associated with the aforementioned events, and (ii) compare between them the population parameters. The parameters we studied were density (ind/m²), sexual proportion, female fertility (i.e., eggs/female), and the relationship eggs/female versus female size. Density (ind/m²) ranged from 0.2 to 0.4 in 1996 and from 0.5 to 0.6 in 1999. ANOVA-tests registered differences in density among study sites and between years. In some of the study sites, females were more abundant than males (e.g., Lomas del Sauce). Females fertility ranged from 27 to 39 eggs per female, with significant differences among sites in 1996 but not in 1999. For females of 30-50 mm body size, a linear relationship was detected between egg number/female and body size. It is concluded that the E. wagenknechti outbreaks are site-specific in the study area and that the demographic parameters examined show a high variability among sites and between events.

Sob certas condições ambientais, diversas espécies de gafanhotos que habitam áreas de campos, como as áreas entre vales do deserto transicional do Chile, podem experimentar surtos populacionais. Uma dessas espécies é Elasmoderus wagenknechti (Liebermann), espécie endêmica. Nós estudamos dois surtos que ocorreram em 1996 e 1999. Os objetivos da pesquisa foram (1) estimar alguns parâmetros demográficos associados aos eventos acima indicados, e (2) comparar os parâmetros entre os eventos. Os parâmetros estudados foram densidade (indivíduos/m²), razão sexual, fertilidade da fêmea (i.e., ovos/fêmea), e a relação entre a fertilidade e o tamanho corporal da fêmea. O intervalo da densidade do evento foi estimado entre 0,2 e 0,4 indivíduos/m² em 1996, e entre 0,5 e 0,6 indivíduos /m² em 1999. Foram encontradas diferenças (análise de variância) na densidade entre os locais para o mesmo evento, e entre os eventos. As fêmeas foram mais numerosas que os machos em alguns locais estudados (e.g., Lomas del Sauce). Foi estimado um intervalo médio de 27-39 ovos/fêmea, existindo diferenças entre os locais no evento de 1996, mas não no evento de 1999. Para fêmeas de longitude corporal de 30-35 mm. foi detectada uma relação linear entre número de ovos/fêmea e tamanho corporal. Em conclusão, a magnitude do evento na área de estudo é específica do local; além do que para os parâmetros demográficos examinados existe uma acentuada variabilidade entre locais e entre os eventos.

Maternal effects on phase characteristics in the desert locust, Schistocerca gregaria: a review of current understanding.

Desert locusts demonstrate pronounced density-dependent polyphenism: a complex suite of traits shifts over the lifetime of an individual in response to crowding or isolation. These changes also accumulate across generations through a maternal effect. Female desert locusts alter the developmental trajectory of their offspring in response to their own experience of crowding. The mother possesses a memory of both the recency and extent of crowding and shifts the phase state of her hatchlings accordingly. Extensive experimental work has shown that offspring behaviour is controlled by a low molecular weight, polar compound (or compounds) released from the mother's accessory glands. The chemical identity of this agent is not yet known.

Histological description of the midgut and the pyloric valve of Tropidacris collaris (Stoll, 1813) (Orthopetera: Romaleidae)

The present research describes the histology of the midgut, gastric caeca, and pyloric valve of Tropidacris collaris (Stoll, 1813), (Orthopetera: Romaleidae). We used light microscopy, staining (Gomori's trichrome and periodic acid-Schiff (PAS)), and a routine histological analysis method (hematoxilin-eosin). The insects were obtained from, and also bred in, the Laboratory of Entomology, Department of Biology, of the Rural Federal University of Pernambuco (UFRPE). The collected material was fixed in alcoholic Boüin and embedded in paraplast. The results demonstrated that the midgut wall is composed of an inner epithelial layer and two outer layers of striate muscles: one internal (circular) and the other external (longitudinal), with connective tissue between the muscle fibers. The epithelium is single-layered, with two cell types: regenerative and elongated columnar. The gastric caeca presents muscle layers similar to those of the midgut. Simple columnar epithelium lines the gastric caeca, which presents villi and projects towards the lumen. The pyloric valve is of striate muscle tissue, covered by a single epithelial-cell layer.

A presente pesquisa teve como objetivo descrever a histologia do mesêntero, cecos gástricos e válvula pilórica de Tropidacris collaris (Stoll, 1813) (Orthoptera: Romaleidae), por meio da microscopia de luz, utilizando-se colorações especiais (Tricrômico de Gomori e P.A.S. - Acido periódico de Schiff) e de rotina (Hematoxilina-Eosina). Os insetos foram obtidos da criação existente no Laboratório de Entomologia, do Departamento de Biologia, da UFRPE. O material coletado foi fixado em Boüin alcoólico e processado para inclusão em "paralast". Os resultados mostraram que a parede do mesêntero é constituída por duas camadas de músculo estriado: uma interna (circular) e outra externa (longitudinal), com a presença de tecido conjuntivo entre as fibras musculares. O epitélio é do tipo simples, constituído por dois tipos de células: células regenerativas e células colunares altas. Os cecos gástricos também apresentam as camadas de músculo semelhantes às observadas no mesêntero. O tecido epitelial é do tipo simples colunar projetando-se para a luz do órgão, formando vilosidades. A válvula pilórica é constituída por tecido muscular estriado, recoberto por tecido epitelial.