This review discusses body size and mass as they relate to the Orthoptera (crickets, katydids, grasshoppers) and the Phasmatodea (walkingsticks). It addresses the expression, causes and consequences of size in these insects. Topics include: methodological problems in body-size research, gravity vs surface forces, allometry and scaling, Dyar's law, ontogenetic scaling, size-invariant traits and nonallometric scaling, the influence of size on physiology, function, behavior, life history, mating, fecundity, population dynamics, ecology, and community, size-clines, Bergmann's rule, sexual size dimorphism, Rensch's rule, protandry, the environmental, genetic, and physiological control of size, the evolution of size and the influence of size on evolution. Hypotheses are presented to explain why insects remain small in comparison to other taxa.

We compared adult body size among six populations of the flightless lubber grasshopper Romalea microptera from south Florida, USA. The most distant populations were 113 km apart. We tested whether size differences among populations are correlated with local mean precipitation or temperature, and specifically investigated whether smaller average size is correlated with climate-related short-growth season, as has been shown for other grasshoppers. We found significant size differences among the populations for both males and females. Mean body size of R. microptera was greatest for a central population at Shark Valley South, declined toward the northwest, and less strikingly, toward the south. R. microptera females had a greater mean size at sites with high precipitation in May and low precipitation in November, suggesting that earlier onset of the wet season is positively associated with mean size. Further, mean size increased with increasing mean minimum temperature in January. These differences in adult size of R. microptera suggest that differences in local environments lead either to evolution of local differentiation in adult size or local differences in growth and development that result in differential expression of phenotypic plasticity in adult size.

The semi-aquatic grasshopper Cornops aquaticum is native to South America and inhabits lowlands from southern Mexico to Central Argentina and Uruguay. It is host-specific to aquatic plants in the genera Eichhornia and Pontederia. A quarantine population has existed in South Africa for 10 y, and it is planned to release it there as a biological control agent of water hyacinth, E. crassipes. Various studies of C. aquaticum are coordinated under HICWA ( www.mpil-ploen.mpg.de). This paper compares the morphometry of the release population and 11 native populations in South America. We tested four hypotheses: 1) South African and South American populations of C. aquaticum differ in morphology; 2) the South African laboratory population is more similar to other isolated populations in South America than to nonisolated populations; 3) morphology differs across sites; 4) morphology differs with host plant. South African populations differed from continental nonisolated populations, but not from continental isolated ones. Isolated populations presented smaller individuals than nonisolated, but there was also a change in male morphology: while in nonisolated populations male wing length was similar to their body length, in isolated populations, male wings were smaller than body length. Females were larger when on Eicchornia azurea than on E. crassipes, while males presented larger wings than their body on E. azurea, and similar lengths on E. crassipes. These morphological changes may have resulted from phenotypic plasticity, selection for small size, or because of a loss of genetic diversity in quantitative traits.

We studied geographic body-size variation in males and females of 25 populations of the South American melanopline grasshopper Dichroplus pratensis Bruner, 1900, along more than 22 degrees of latitude (S) and between 0 and almost 2500 m of altitude. Using mean body length of each sex and factors obtained from PCA analyses of six morphometric linear characters, it was shown that D. pratensis follows the converse to Bergmann's rule, becoming smaller at higher latitudes and altitudes. Variability of body size increased with latitude and altitude in males and females. Body-size trends were statistically significantly correlated with ambient temperature (annual mean, minimum and maximum), precipitation (annual mean, minimum and maximum), and two estimators of seasonality, the difference between the maximum and minimum temperatures, and the difference between maximum and minimum precipitation for each locality; both nonparametric correlations were positive. Body size was also positively and significantly correlated with Actual Evapotranspiration (AET), a measure of primary productivity, and with Potential Evapotranspiration (PET), a measure of ambient energy, but not with water balance (WB). Some allometric relationships also showed geographic variation. We suggest that the observed decrease in size with latitude and the increase in morphological variability, are joint consequences of the shortening of the growing season towards the south, the increasing seasonality and climatic unpredictability, lower primary productivity (as represented by AET); and that the species exhibits protandry, which contributes in the south, to smaller and more variably sized males, and smaller but more constant body size in females.

We examined size clines for various external body structures in two grasshopper species (Chorthippus vagans and Oedipoda miniata) and one katydid species (Poecilimon birandi), along an altitudinal gradient ranging from sea level to 1,980 m in southwest Anatolia (Turkey). In O. miniata and P. birandi all measured structures (body, tegmina, pronotum, and hind femur) were smallest at the highest altitude for both sexes. Hence, in these species, different structures covaried in the same direction, with increasing altitude. In contrast, there was no clear relationship between altitude and size in C. vagans, and different structures covaried in different directions in males and females (i.e., some structures became larger at higher elevations, whereas others became smaller, and this differed with sex). For some other C. vagans traits, there was no significant intraspecies variation. Hence, O. miniata and P. birandi followed the converse Bergmann's Rule, whereas there was no consistent pattern for C. vagans. For C. vagans, small body size was not associated with either local population density (measured as relative abundance) or local species richness, suggesting that neither intra- nor interspecific competition determined body size for this species. For O. miniata, the smallest individuals were found at the site with the highest grasshopper diversity, suggesting that interspecific competition could have influenced O. miniata body sizes at this altitude. However, the largest O. miniata individuals generally occurred at the sites with the highest relative abundance of O miniata. Hence, in this species, body sizes were generally larger at sites with high population densities — consistent with sites that were most favorable and so able to support high densities of O miniata also producing the largest individuals of this species. Observational data on P. birandi similarly suggested that, for this katydid, there is little relationship between local diversity/abundance and altitudinal size-clines.

We analyzed geographical variation in body size in males and females of nine Greek populations of the bushcricket Poecilimon thessalicus Brunner von Wattenwyl, 1891. We found significant geographic variability in P. thessalicus, with all three morphometric body-size characters (hind femur, front tibia, and pronotum) highly correlated within populations. Populations differed in mean size between three mountain ranges, and were larger on moist eastern, than on dry western slopes. We suggest that the observed smaller size of the bushcrickets on western slopes is mainly the consequence of a shorter growing season due to summer drying on western slopes. Sex-specific growth rates might contribute to the observed smaller body size in males in all populations. Rensch's rule that sexual size dimorphism (SSD) decreases as body size increases is supported, with males growing relatively larger compared to females in populations with larger body sizes. This pattern might be sexually selected, as males that produce larger nuptial gifts are favored as mates in Poecilimon bushcrickets.

We studied geographical body-size variation and sexual size dimorphism in three isolated populations of the bush-cricket Pholidoptera frivaldskyi in Central Europe (Slovakia). We measured six body traits in females and seven in males, from 93 individuals (46 males and 47 females): lengths of body, right hind femur, right hind tibia, pronotum, right cercus or ovipositor, length of wing (only in males) and body weight. Not all linear traits in both sexes were correlated with body weight. Generally, females were significantly bigger than males in all parameters. Although discriminant function analysis indicated some significant differences in male traits, there were no strong morphological difference among local populations. Morphological variability among the three populations was not higher than that within populations. This relative somatic uniformity should be verified on the level of genetic variability of the studied populations, since cryptic species diversity can be expected.

We studied 12 species of Acrididae (4 Oedipodinae and 8 Gomphocerinae) associated with three ecological stages of succession in herbaceous environments in mine tailings near Limoges, France. The pioneer, medium and late stages of succession each contained four different dominant grasshopper species. We measured morphometry variables possibly linked with displacement (locomotory) capacities, taking advantage of previous analyses on walking and jumping-flight performances on the same species.

Early succession species were characterized by long hind and fore wings and a wider pronotum. Their wings also exhibited greater sexual dimorphism in length than grasshopper species from middle or late successional stages. These morphological characters are associated with jumping-flight performances and walking speed, because the best jumpers are the best walkers. Although the ratio of wing length to body length decreases with succession, the overall body size does not, and overall body size is not correlated with displacement performance.

Complex interactions between an individual's genotype and its environment determine characteristics such as body size. However, gene-environment interactions should not be seen as being restricted to individual ontogeny: the diversity of the local gene pool can be greatly influenced by habitat variables and population history (e.g., landscape connectivity and propagule size). In this paper I use a model species, the bushcricket Metrioptera roeseli, and data from long-term experimental population introductions to examine individual body size as an indicator of the constraints placed on the gene pool by ecological variables following colonization of new environments. These broad-scale population-environment interactions are useful in understanding species ecology, species invasions and in managing successful reintroductions in conservation biology.

Sexual size dimorphism (SSD) is a common phenomenon in animal taxa. While males are the larger sex in many birds and mammals, female-biased SSD predominates among insects, including Orthoptera. We analyzed size differences of 1503 Orthoptera species, suggesting that SSD is rather uniform in Ensifera, with the females being on average 9% larger than the males (ranging from −20 to 40%). In contrast, SSD is usually much stronger in Caelifera (37%) and also more variable (ranging from −20 to 140%). Caelifera with larger females exhibit stronger size differences than smaller species, whereas in Ensifera SSD decreases with male body size, but is not related to female size. Sexual size differences in Orthoptera are usually associated with a higher number of nymphal instars in females, leading to an earlier emergence of adult males (protandry). Both growth rates and the number of instars seem to be affected by genetic and environmental cues. Two major hypotheses have been proposed to explain the ultimate causes for SSD: the intersexual competition hypothesis and the differential equilibrium hypothesis. The first suggests that sexual dimorphism is a mechanism to reduce intraspecific competition, enabling the sexes to specialize on different food items. The differential equilibrium hypothesis proposes that the different body sizes represent sex-specific fitness optima, which are caused by their specific life-history strategies. Females may maximize their reproductive success by increasing the number (or size) of eggs (fecundity selection), whereas males may maximize their reproduction by being more mobile and fertilizing many females in a short period of time. These fundamental differences in the life-history strategies of the sexes may also lead to sexual selection, which has sometimes been referred to as an additional hypothesis. There is still a need for more empirical research on the ultimate causes for SSD. At present, there is much more support for the differential equilibrium hypothesis, but the intersexual competition hypothesis has rarely been tested. We propose some experimental approaches to test both hypotheses in micro- and macroevolutionary contexts.

Sexual size dimorphism (SSD) in animal species can result from the interplay between natural and sexual selection. In this paper we review the impact of sexual and natural selection on grasshopper body size and the evolution of SSD. Mate choice by females, and natural selection on female fecundity could explain an evolutionary trend to increase SSD in species in which females receive nutritional benefits during mating. In general, sexual selection is stronger in males than females. However, when females receive nutritional resources from males during mating, selection could be stronger in females than males. These resources constitute high energetic costs to males and it is expected that this promotes an increment in male mate selectivity. Higher female-biased SSD might evolve as a result of polyandry in species where males transfer nutritional benefits in the ejaculate. This hypothesis is testable at both macro- and microevolutionary levels. Finally, we discuss the relationship between body size and mate-guarding duration and its evolutionary implications and propose future studies to analyze the evolution of SSD and mate-guarding duration in grasshoppers.

Sexual size dimorphism (SSD) can be the result of sexual selection (SS) or natural selection (NS). Due to male-male competition for access to females, SS could favor an increase in male body size. On the other hand, larger size in females could be favored by NS, since egg production is directly correlated with body size. Rensch`s rule states that SSD increases with increasing body size in animals, where males are the larger sex, and decreases when females are larger than males. Thus, Rensch's rule predicts that in those insects where females are larger than males, SSD should decrease with increasing body size, when comparing populations and species. We analyzed SSD in 19 Argentine populations of the grasshoppers Dichroplus vittatus and 25 of D. pratensis. Both species show latitudinal and altitudinal variation in body size, following the converse to Bergmann's rule: body size decreases with increasing latitude and decreasing ambient temperature. SSD occurs in both species across their geographical distribution ranges, also involving differences in allometry and shorter developmental times in males. In D. vittatus, the degree of SSD increased significantly with general body size, whereas in D. pratensis SSD decreased as body size increased. A plausible explanation of SSD is that SS favors a differential increase in female body size related to a preference by males for more fecund females. Given the close phylogenetic relationship between both species, the differences in SSD between them may be the result of differential natural and sexual selective pressures. In D. vittatus both sexes could be reacting differently to environmental conditions regarding body size, while in D. pratensis protandry could be the main factor behind SSD.

Sinipta dalmani is an Argentine grasshopper whose chromosome polymorphisms have been widely studied through cytogenetic and fitness-component analyses. This paper reviews the available information on its body-size variations as they relate to differences between sexes, karyotype and mating success, and shows a preliminary analysis of a pattern of geographic variation. A significant body-size sexual dimorphism was evident, with females being significantly larger than males. Polymorphic populations for M₄ pericentric inversion showed considerable variation in both adult male and adult female sizes, a variation in part related to this chromosomal rearrangement, which has a negative effect on body size. Simultaneous cytogenetic, morphometric and fitness analyses showed direct evidence of phenotypic directional selection within populations favoring larger males and smaller females. The patterns of body-size differentiation among populations in relation to geographic conditions suggest local adaptation. Our results in S. dalmani demonstrate significant variation in body size within polymorphic populations and among geographical populations, which may be explained under a selective scenario.

Conspicuous sex differences in size, shape, color and behavior are pervasive throughout both the animal and plant kingdoms. Although previous work has shown that sexual dimorphism can evolve purely as the result of either natural (intersexual resource competition) or sexual selection (fecundity selection, male-male combat), a handful of studies have also shown that these mechanisms need not be mutually exclusive and may even act synergistically to enhance dimorphisms. More recent studies have focused on the factors that act to constrain the evolution of sexual dimorphism. For example, a high genetic covariance among traits between the sexes is thought to retard adaptive sexual differentiation or place an upper limit on the degree of intersexual divergence. However, high genetic correlations themselves are often the result of selection for functional coherence amongst traits (integration), and thus divergent selection between the sexes could theoretically drive sexual dimorphism in the genetic variance-covariance matrix (G). To address this issue, we consider the phenotypic variance-covariance matrix (P), within the context of the evolution of sexual dimorphism in the eastern lubber grasshopper (Romalea microptera). We show that: 1) adult female lubbers have relatively wider heads than adult males; 2) most morphological traits show significant integration with one another, but males show a higher degree of integration than females; 3) P in lubbers is not strongly correlated across the sexes. These results suggest that phenotypic integration does not constrain the evolution of sexual dimorphism in R. microptera. Hence, sex-related traits can evolve separately from other traits.

Insects are predicted to prefer larger partners for a number of reasons relating to fitness. In species where males provide an expensive nuptial gift, male and female preferences for a larger partner are likely to be more pronounced. In nuptial-feeding insects however, models of sperm competition and female choice predict that males and females should also prefer virgin partners. Here we test the relative importance of size vs virginity in a Greek bushcricket, Poecilimon laevissimus, in which males offer typically large nuptial gifts during mating. While only a small number of replicates could be implemented, and there is a clear need for further analysis, we found that all males and females preferred to mate with virgins, despite the fact that nearly 90% of the virgins were smaller in size than the nonvirgins offered. In terms of mate choice, virginity therefore appears more important than body size in P. laevissimus.

During mating, male insects of certain species transfer a costly nuptial gift, a large spermatophore, which is eaten by the female as sperm transfer into her. The spermatophore components (the sperm-free spermatophylax and the sperm ampulla) vary greatly in size between species, and have a direct influence on male fitness. Studies of the relationship between spermatophore size variation and male fitness have concentrated on associations between evolutionary changes in spermatophylax size and either ampulla size or sperm number. Two main hypotheses have been put forward to explain the function of the spermatophylax: the ejaculate-protection hypothesis and the paternal investment hypothesis. A strong correlation between the spermatophylax and ampulla or sperm number suggests an ejaculate-protection function because it protects the ampulla from being removed prematurely. However, comparative support comes mainly from disparate bush-cricket species (Tettigoniidae), that vary greatly in relatedness and diet. Furthermore, data are often from animals reared under laboratory conditions. Our study describes the significance of size variation in bush-cricket nuptial gifts, with an analysis from field populations of 33 species within the genus Poecilimon. Poecilimon share similar diets and the variation in spermatophore size within the genus approximates family-wide variation, so confounding influences from diet and relatedness are, to a certain extent, controlled. Previous support for the ejaculate-protection hypothesis is almost universal, so we expected to find similar results. However, unlike previous studies, there was no relationship between body mass and each of the three spermatophore components when body mass was accounted for, or between spermatophylax mass and sperm number. We also found only a weak relationship between ampulla mass and sperm number, suggesting that caution is needed when using ampulla size to predict sperm number or sperm number to predict ejaculate size. In support of the ejaculate-protection hypothesis we found a positive relationship between spermatophylax size and ampulla mass. While our results support the ejaculate-protection hypothesis, they are not inconsistent with the paternal investment hypothesis.

In many insect species, males with larger body sizes are more successful at securing mates. Previous studies on the brachypterous grasshopper Podisma sapporensis have shown that male mating frequency varies greatly among populations. Here we test the hypothesis that differences in male mating success among populations are linked to differences in body size and shape. To do so, we collected males and females from three localities and conducted cross-breeding experiments. Overall, we found no link between mean male body size and mean number of matings across populations. However, stepwise regression indicates that within the populations, males with longer thoraxes and shorter hind femurs, mated more frequently, whereas females with longer thoraxes mated more frequently. These results suggest that in males, having short hind femurs, relative to body size, rather than body size itself, contributes positively to mating success — perhaps because of an advantage in holding onto females while avoiding females' resistance.

We used linear regression, nonlinear regression and principal component analysis to examine the relationships among morphology, fecundity, and mating variables for lab-reared adult female Romalea microptera (Beauvois) (fam. Romaleidae) grasshoppers. Morphological variables included head width, pronotum length, femur length, adult eclosion mass, maximum mass reached before the 1^st oviposition, and maximum mass reached before the 2^nd oviposition. Fecundity (= reproductive) variables included clutch size Pod 1, clutch size Pod 2, total eggs Pods 1 2, mass Pod 1, mass Pod 2, time between adult eclosion and Pod 1, time between Pod 1 and Pod 2, and time between eclosion and Pod 2. Mating variables included number of matings and age of 1^st mating. Most morphological variables were strongly positively correlated, and morphological variables (especially femur length, eclosion mass, and maximum body mass reached prior to oviposition) predicted many fecundity variables. Maximum body mass reached prior to laying Pod 1 was highly correlated with maximum body mass reached prior to laying Pod 2 (r =0 .93), and clutch size Pod 1 predicted clutch size Pod 2 (r = 0.72). However, time to oviposit (= interval between adult eclosion and oviposition) was generally unrelated to body size, body mass, or clutch size or mass. Hence, clutch size and pod mass are strongly determined by body size and mass at adult eclosion, but timing of oviposition is independent of body size and mass at eclosion. The results also suggest that early mating speeds oviposition, but that excessive mating reduces female fecundity, as measured by clutch size.

Body size affects many aspects of an organism's performance, including reproduction. Ecologists have shown an increased interest in linkages between body size variation and population dynamics. Fecundity in a number of insect orders is often positively correlated with body weight or structural size, but reproductive characteristics and body size are not always positively correlated, particularly in field studies. Numerous biotic and environmental factors can influence individual body size and reproduction in grasshoppers under field conditions. Intraspecific relationships between reproductive traits and individual body size in melanopline grasshoppers were examined using data from four field experiments. Significant positive correlations between body size and reproductive traits occurred in three of four field experiments involving Melanoplus sanguinipes (Fabricius) and Phoetaliotes nebrascensis (Thomas) where per capita resource availability was manipulated, with a highly significant relationship between femur length and functional ovarian follicles when statistical results were combined from all correlations. In addition, individual femur length was a significant covariate for at least one reproductive trait in three experiments. Biotic factors such as food availability and predation could be more important than body size in determining reproductive output under field conditions, but further work is required to examine under what conditions individual body size affects reproduction in grasshoppers.

Body size is of primary interest to biologists because of its often positive correlation with fitness, in particular fecundity. The size-fecundity relationship is well established both within and among species. However, little is known about how the size-fecundity relationship differs among populations of the same species or whether it differs in response to environmental conditions experienced by a single population. This study examines the size-fecundity relationship in the pallid-winged grasshopper (Trimerotropis pallidipennis: Acrididae, Oedipodinae) among seven populations that extend along an aridity gradient in the southwestern United States. Results showed a positive relationship between body size of field-caught females and precipitation along the gradient, but only among those populations that receive less than 12 cm rainfall a year. There was a positive relationship between body size and the number of mature oocyte in the ovaries and with the number of hatchlings. Potential fecundity, measured as the number of ovarioles, was not correlated with body size in any analysis. All analyses showed that populations differ in their size-fecundity relationships. This relationship was also examined in laboratory conditions that mimic years of high,versus low, food abundance. Results indicate that across the whole aridity gradient, the size-fecundity relationship is largely a function of available resources. The populations at the xeric end of the gradient however, change their reproductive strategy in years of low food abundance and invest more into reproduction per unit size than they do in years of high food abundance. Together, these results caution against assuming, a priori, a positive relationship between size and fecundity; results indicate this relationship depends on the measure of fecundity used, that populations can differ in this relationship and that this relationship can change with changes in environmental conditions. Last, when examined among individuals, body size explained less than 20% of the variation in fecundity, suggesting that body size is not the main determinant of reproductive success in this species.

Life-history models predict populations under shorter growing seasons will invest earlier and more heavily in reproduction than populations under longer growing seasons. Populations of Romalea microptera inhabit distinctly different climates and differ in mtDNA cytochrome-b gene sequences. Previous work suggested a latitudinal trend in the trade-off among body-mass gain, age at first oviposition, and clutch mass, in populations from Miami FL, Lydia LA, and Athens GA: but this study was confounded by longitudinal variation. Hence, we compared the Miami and Athens populations to a population from Jacksonville, FL, which is equidistant from both, yet under a distinct climate. The Athens population had less body-mass gain and an earlier age at oviposition than the other two populations. When corrected for initial body mass or age at oviposition, the Athens population produced larger clutches. Developmental profiles of juvenile hormone and hemolymph lipids did not differ across populations. In comparison to the Miami population, the Jacksonville population showed a nonsignificantly greater body-mass gain and age at oviposition, in contrast to the latitudinal trend observed previously. These data suggest that reproduction in R. microptera involves a trade-off between body-mass gain and age at oviposition, which is consistent with a current vs future reproduction trade-off.

Life-history theory suggests that the existence and persistence of phenotypic variation within species must be maintained through some advantage accruing to an individual following one developmental pathway over another. Here, we consider the adult lifespan of two highly differentiated male morphs and the female in the bladder grasshopper species Bullacris membracioides (Orthoptera: Pneumoroidea). Our results show that the adult longevity of small, uninflated males is twice that of both the larger inflated male and mature females. Uninflated males have a type II survivorship curve, whereas inflated males and adult females both have type I survivorship curves. This difference indicates that the latter two morphs die due to senescence, while the uninflated male does not. The longevity difference between the male morphs shows that while the volant inflated males have the ability to locate many females, they can do so only over a short term, whereas the flightless uninflated male has comparatively limited mobility, but twice as much time to search for mates. This lifespan extension may impart some reproductive advantage for the uninflated male in the longer term, allowing for more female encounters, and increasing its chances for reproduction.

Variation in body size exists within any natural population. Moreover, variation in this fundamental physiologically based trait often translates into variation in demographic rates. Here we explore the effects of variation in the initial body size of individuals on the mean survival trajectory of a generalist herbivore living in a seasonal environment. We first present the results from an individual-based model, which provided expectations for the form of the relationship between mean survival and standard deviation in initial size. We then develop a heuristic analytical model that captures the essentials of the influence of initial-size variation on mean survival to end of season. Both theoretical formulations demonstrate that as initial body size variation increases, mean survival might initially increase; however, this initial positive effect is eventually reversed, causing mean survival to fall steeply as size variation becomes high. We then test these qualitative predictions in the field by manipulating the magnitude of initial size variation in experimental populations of the generalist grasshopper, Melanoplus femurrubrum. We show good qualitative congruence between model predictions and experimental results. Because herbivore survival is strongly linked to the strength of food-web interactions, we suggest that adopting such a combined theoretical and empirical approach can provide a profitable avenue toward a full understanding of the interplay between individual trait variation and higher-level dynamics.

Morphometric condition (i.e., condition estimated from some aspect of body size) is frequently calculated from mass-size residuals, and is often used to infer something about an animal's energetic state. However, controversy exists about the validity of using mass-size residuals for this purpose. Recent work suggests the approach is appropriate in mammals, but it is unclear if morphometric condition is useful in the context of understanding the energetic state of grasshoppers and whether differences in morphometric condition are associated with variation in fecundity-related characteristics in females. To address this question, I examined male and female Dactylotum variegatum, sampled from a mosaic of grazed and ungrazed grasslands in southeastern Arizona, to determine whether morphometric condition corresponded with lipid and glycogen levels in males and a variety of reproductive characteristics in females. D. variegatum was found to be strongly sexually dimorphic relative to mass and femur length. The relationship between mass and femur length was linear for both males and females, an important assumption underlying the use of mass-size residuals as a measure of condition. Structurally larger males had more lipid and glycogen content. After controlling for the effect of size on lipid and glycogen content, a positive relationship was found between morphometric condition and lipid and glycogen levels, although the relationship was relatively weak for glycogen. In females, femur length, mass, and morphometric condition were not significantly associated with the number of ovarioles or the mean number of eggs or corpora lutea per ovariole. Only the mean number of resorption bodies per ovariole was significantly related to mass and morphometric condition, with larger and better conditioned females having fewer resorption bodies. The results of this study suggest that mass-size residuals in this species of grasshopper are related to energetic condition, but that other factors, such as variation in water and protein content, may weaken the relationship. Morphometric condition probably has limited value in estimating fitness of wild-caught D. variegatum females.

Metabolic rate determines an individual's rate of resource acquisition, assimilation, growth, survival and reproduction. Studies involving a broad range of taxa and body sizes typically result in whole-organism metabolic rate scaling to the ¾ power of body mass. Competing models have been proposed to explain this allometric relationship. The nutrient supply network model of West et al. (1997) proposes that the ¾ power relationship results from the fractal nature of space-filling nutrient supply networks. The model of Kozlowski et al. (2003) proposes that the scaling of metabolic rate with body mass will vary from 2/3 to 1 among different taxa, depending on the degree to which increasing body size depends on increasing cell size or number. The present study measured resting metabolic rates across a broad range of body sizes in nymphs of Melanoplus sanguinipes F. and also analyzed published reports of metabolic rates in adult Orthoptera. The two sets of data were in close agreement: the scaling exponent for the ontogenetic series of M. sanguinipes was 0.92, and for the interspecific, phylogenetically corrected regression with adult Orthoptera, was 1.06. Both scaling exponents were significantly greater than the 0.75 predicted by the nutrient supply network model.

Grasshoppers, like all other organisms, are composed of a combination of elements, but little is known about the extent to which the elemental composition in grasshoppers changes over the course of nymphal development. In this study the grasshopper Schistocerca americana was reared on a diet of seedling wheat and wheat germ; nymphs of various mass were collected and analyzed for elemental composition. In total, 12 different elements, including the macroelements carbon, nitrogen, and phosphorus, were quantified. Results show that the amount of a given element increased linearly with increasing body mass, but that the rate of increase differed depending on the element. Results also show that the concentration of some elements dropped dramatically over the course of development. We discuss our results in the context of limiting nutrients and ecological stoichiometry.

Autotomy, the ‘voluntary’ shedding of a limb or other body part, is a highly effective escape mechanism to avoid predation or other forms of entrapment. Autotomy, however, comes with costs to locomotion, reproductive behavior, regeneration etc. It has been suggested that increasing body size and ‘robustness’ may allow for less reliance on this extreme form of predator defense, but this theory has never been tested. Here we present behavioral observations (‘willingness’ or time taken to lose an entrapped limb) of Orthoptera of a range of body size and mass. These data strongly suggest that body size and mass may be an important determinant of the use of autotomy as an escape mechanism within the Order, possibly due to the effects of body size upon the efficacy of autotomy, as well as other defense mechanisms. An ontogenetic study for Gryllus bimaculatus, however, shows no clear trend in willingness to autotomize a limb with body mass, suggesting that this defense tactic may be less affected by body size per se, but rather by the tactics developed by each individual species.

Scientific literature often touts the many advantages of large body size, but seldom addresses the value of small body size. Yet selection for large size must be counterbalanced by selection for small size, otherwise, all animals would be large. In this paper, we demonstrate female-biased size dimorphism and a strong copulatory advantage for small males in a Jerusalem cricket (JC) (Stenopelmatus) from central California. We selectively paired male and female JCs of diverse body sizes and recorded their ability to copulate. All copulations were successful for males smaller or equal in size to females. In contrast, when the male was 6.1 mm longer than the female, copulation had only a 50% chance of occurring successfully. In general, as the difference between male and female body length increased (i.e., as males became longer than their mates), the probability of successful copulation decreased. These patterns of mating resulted in net selection for small male size and large female size. We also detected positive linear direct selection on male hind leg length, which may explain why male JCs have longer legs than females. The copulatory disadvantage of large males derives from the odd mating behavior of this group, in which males must contort and precisely align their bodies to couple. We believe that this is the first example of small-male advantage based solely on the physical aspects of copulation. In this species, small, not large, males have a copulatory advantage.

Among crickets and katydids calling carrier frequency is often inversely related to body size. Within species, this relationship is so far found consistently for species employing nonresonant stridulation, but not always among those using resonant stridulation. Metrioptera sphagnorum, is an unusual acoustic species in making two different spectra, one by nonresonant, one by resonant, stridulation. The nonresonant carrier of this insect correlates inversely with body size; the carrier of the elastic-resonant song part does not. Complex-wave pulses made over the distal half of the stridulatory file, give a nonresonant spectrum with a broad audio band, peaked near 19 kHz; sinusoidal pulses, made over the proximal half of the file, give an ultrasonic peak near 35 kHz. The sometime absence of a body-size effect in resonant stridulation may arise from the importance in this mechanism of tooth-contact rates: these provide a way of affecting carrier independent of isometry. Another possible factor in expressing body size acoustically is that nonresonant radiators may show less departure from natural vibration modes. Sound intensity in M. sphagnorum, though affected by temperature, could not be correlated with size.

We investigated the relationship between body size (weight) and hearing sensitivity in response to a high-frequency, bat-like stimulus in a number of phaneropterine katydids on BCI, Panama. These phaneropterines are nocturnal flying species and thus potential prey of various insectivorous bats on the island. We tested the prediction that larger species compensate for the disadvantage — of producing stronger echoes for searching bats — by being more sensitive to bat calls, thereby increasing safety margins towards this predator. Contrary to this prediction, larger katydids were not more sensitive. This was corroborated in neurophysiological experiments in the nocturnal rainforest, where simultaneous recordings of the T-fibre activity in response to searching bats revealed no substantial difference between small and large katydids. We offer three explanations for the lack of correlation between body size and high-frequency sensitivity in these species.

Body size is a crucial element of an organism's ecology and evolution, and is known to be influenced by natural selection. Here, we estimated the strength of temperature-mediated selection on body size in a wild population of the striped ground cricket, Allonemobius socius. We found that extremely high, but naturally occurring temperatures, selected for larger body sizes, as expected. The strength of this selection pressure was strong, with the univariate selection gradients being β = 0.591 ± 0.237; β_σ = 0.281 ± 0.112; and β_μ = 3.95 ± 1.58 (± s_x̄). These results suggest that periodically occurring temperature extremes can influence the evolution of body size in wild populations of A. socius and other orthopterans. Furthermore, these selection pressures may contribute to the often observed size cline known as the Converse of Bergmann's rule, and become more prevalent in the future as temperatures increase due to global warming.

Although large size is considered an evolved antipredator defense for some vertebrates and shellfish, large size is generally not considered an adaptive defensive trait in insects. Here we propose that large size in chemically defended grasshoppers has evolved as a beneficial antipredator trait. The lubber grasshoppers Romalea microptera and Taeniopoda eques are the largest grasshoppers in North America north of Mexico. These closely related species escape most vertebrate predation by possessing powerful predator-deterrent toxins and by nocturnal roosting. We hypothesize that escape from vertebrate predation allowed lubbers to evolve a larger body size, increased fecundity and provided many other benefits, including defense against invertebrate predators. To test the hypotheses that large lubber size reduces predation, we conducted feeding trials with wolf spiders (Honga carolinensis), assassin bugs (Arilus cristatus), preying mantids (Tenodera aridifolia), fire ants (Solenopsis invicta), frogs (Rana pipiens), and birds (Sturnus vulgaris and Passer domesticus). Our results show that larger lubber instars enjoyed a highly significant advantage vis-à-vis predators, demonstrating the adaptive value of large size against both vertebrate and invertebrate predators. Adult lubbers were generally immune from predation. It appears that lubbers have evolved to occupy a relatively predator-free ecological space: they are too large to be attacked by most invertebrate predators and too toxic for most vertebrate predators. We propose an evolutionary scenario whereby a change in feeding behavior toward vertebrate-toxic plants served as an evolutionary breakthrough, setting in motion the subsequent evolution of increased chemical defense and large body size in lubbers. To determine if large size is associated with chemical defense in grasshoppers in general, we compared body sizes of ~ 40 toxic vs ~ 3,000 nontoxic grasshopper species. Our results show that chemically defended species tend to be larger than nondefended grasshoppers, supporting an association between chemical defense and large size in insects. Large size may be favored in insects when vertebrate predation is removed as a strong selective factor.