Macropterous Individuals Research Articles

Morphometric variability of specimens in Ground Beetle (Carabidae) communities in agrarian landscape forests and protected areas

The change in the morphometric variable of ground beetles as well as in their volume (ellipsoidal biovol-ume) indicates the state of the biotope (unstable, stable), which is affected by anthropogenic activity such as forestry, agriculture and urbanisation. Between the years 2020 and 2022, we conducted research in flood-plain forests, which were located in agriculturally used land and in the important European territory of Du-najské Luhy Protected Landscape Area. Using the pitfall traps method, we recorded 1319 individuals be-longing to 29 species of ground beetles in six study areas representing two types of habitats (willow-poplar floodplain forest and regenerated poplar forest). We confirmed the largest average Ellipsoid Biovolume (EV) in the species Carabus coriaceus L. (2936 mm3), Carabus scheidleri Panzer (1427 mm3), Carabus vio-laceus L. (943 mm3), Carabus granulatus L. (366 mm3), Cychrus caraboides (L.) (336 mm3), Pterostichus niger (Schaller) (254 mm3), Harpalus rufipes (DeGeer) (123 mm3). The redundancy analysis confirmed the predominance of apterous and brachypterous species of ground beetles in forest stands in the Dunajské Luhy PLA (important European territory). These groups of Carabidae point to the ecological stability of bio-topes, because they inhabit habitats where they have optimum food. On the contrary, we confirmed the pre-dominance of macropterous species in forest biotopes in agrarian landscape conditions, which points to bi-otopes cyclically disturbed by anthropogenic activity. We recorded larger individuals in groups of apterous and brachypterous species in forest stands in the conditions of the Dunajské Luhy PLA. Larger macropter-ous individuals were recorded in forest stands in agrarian landscape conditions. In order to preserve forest habitats of European importance, it is necessary to know the ecological interactions between the ecosystem and ground beetles.

Megamelus scutellaris (Berg) (Hemiptera: Delphacidae) biology and population dynamics in the highly variable landscape of southern Florida

Changes to the historical flow and nutrient levels of freshwater bodies in Florida have made control of waterhyacinth difficult. Biological control agents were introduced to augment herbicidal control of this plant. The newest insect agent, Megamelus scutellaris, was released in 2010, has established, and has been documented dispersing more than 6 kms away from release locations, across aquatic and terrestrial habitats. These insects were able to successfully disperse away from herbicide treated areas and across terrestrial habitats to reach new mats of waterhyacinth. Macropterous individuals were the first M. scutellaris documented at three non-release sites, indicating that the established wild populations are producing flighted individuals and are dispersing actively. Established populations appear to have reached an equilibrium density of 10.74 ± 19.74 M. scutellaris/m2 and this does not fluctuate with additional releases.

Wing polymorphisms of Pterostichus melanarius (Coleoptera: Carabidae) (Illiger, 1978) in Alberta pulse crops

In a 6 week research project, a wing-dimorphic carabid species was studied to identify the proportions of macropterous (large functional wings) individuals and brachypterous (short, rudimentary wings) individuals from different pulse growing regions of Alberta. Pterostichus melanarius I. (Coleoptera: Carabidae) can be short-winged (SW) due to brachyptery being a dominant gene or long-winged (LW) individuals causing macroptery. Although macroptery is a recessive trait, the LW morph persists through the recolonization of populations due to human disturbance. Their ability to fly facilitates their dispersal across Alberta to uncolonized areas. Samples of P. melanarius were captured as bycatch from pea leaf weevil, Sitona lineatus L. (Coleoptera: Curculionidae) pitfall traps from the East, Capital, and Central regions of Alberta. Traps were positioned on a 175 meter transect pea and faba field margins in spring and again in the fall. Captured P. melanarius were identified and separated by collection site and date and stored in 95% ethanol until measurements. The beetles from the bycatch samples were sexed using tarsal characteristics. Anterior tarsal segments of the front pair of tarsi are dilated in males and normal in females. After being identified and recorded as “M” or “F”, they were mounted on a foam board with insect pins for measurement. The elytra (forewings) length and width was measured followed by measurement of their hindwings. They were classified as “SW” or “LW” depending on the functionality of their wings. Out of 440 individuals from the Capital region, 17.1% of captured P. melanarius were LW and 83.0% were SW. From the Central region 21.6% of 495 beetles were LW and 83.4% of them were SW. In the East region less P. melanarius were captured and from 94 individuals, 46.8% were LW and 53.2% were SW. Macropterous individuals are more common in the East region due to recolonization of populations whereas in the Central and Capital region the proportions of SW are much larger. In regions that have established populations of P. melanarius the proportions of SW are greater than LW.

The latitudinal uniformity of the unique life history of <i>Velia caprai</i> (Heteroptera: Veliidae) and notes to the pre-overwintering period of selected water striders (Heteroptera: Gerridae)

Temperate water striders (Gerridae) overwinter as adults and die after spring reproduction. European water cricket Velia caprai (Veliidae) overwinters concurrently in egg and adult stage in Central Europe. This rare overwintering strategy goes with longevity ofthis species. Adults can survive two winters in Central Europe, unlike other semiaquatic bugs. Scandinavian populations of V. caprai and water striders Gerris lacustris and G. lateralis were examined at the beginning and end of September to determine their life histories. Both gerrids start to overwinter during September, females prior to males and macropterous individuals prior to brachypterous. All females of G. lacustris and G. lateralis enter reproductive diapause before winter. V. caprai overwinters in both adult and egg stage in Norway, and can probably survive two winters. Central European and Scandinavian populations of V. caprai share the same unusual way of overwintering and probably also the whole life history.

Seasonal differences in body mass and circulating metabolites in a wing‐dimorphic pygmy grasshopper: implications for life history?

1. Functional wing polymorphism in insects is an intriguing topic, especially with respect to the adaptive advantage of each wing morph. The common pygmy grasshopper in Germany, Tetrix subulata, displays wing polymorphism skewed towards macropterous (LW) individuals capable of flight. Furthermore, T. subulata is known to undergo adult diapause in winter and reproduce in spring.2. Morphometric and biochemical parameters were examined in field‐collected grasshoppers during autumn and spring to obtain a ‘snapshot’ from the same/one cohort of grasshoppers in the wild.3. Flight muscles are largely reduced in brachypterous (SW) specimens, whereas they are well developed in LW individuals. Body mass measurements indicated gain in female T. subulata in spring, especially in LW morphs, which could be attributed to increased reproductive activity (egg production).4. Metabolic fuel in haemolymph is differentially distributed in autumn: the concentration of lipids is highest in males, while carbohydrates are most abundant in LW specimens. The metabolic data imply that dispersal in T. subulata is predominantly in autumn, by flight in the case of LW specimens and by hopping/walking in males.5. The season seems to be an important factor for the reproductive versus dispersal trade‐off in this species. Moreover, this study shows that morphological differences in T. subulata individuals are reflected in physiological differences that may ultimately affect behaviour and ecology.

Spatial Variation in Body Size and Wing Dimorphism Correlates With Environmental Conditions in the Grasshopper Dichroplus vittatus (Orthoptera: Acrididae).

Wing dimorphism occurs widely in insects and involves discontinuous variation in a wide variety of traits involved in fight and reproduction. In the current study, we analyzed the spatial pattern of wing dimorphism and intraspecific morphometric variation in nine natural populations of the grasshopper Dichroplus vittatus (Bruner; Orthoptera: Acrididae) in Argentina. Considerable body size differences among populations, between sexes and wing morphs were detected. As a general trend, females were larger than males and macropterous individuals showed increased thorax length over brachypterous which can be explained by the morphological requirements for the development of flight muscles in the thoracic cavity favoring dispersal. Moreover, when comparing wing morphs, a higher phenotypic variability was detected in macropterous females. The frequency of macropterous individuals showed negative correlation with longitude and positive with precipitations, indicating that the macropterous morph is more frequent in the humid eastern part of the studied area. Our results provide valuable about spatial variation of fully winged morph and revealed geographic areas in which the species would experience greater dispersal capacity.

Elevenin regulates the body color through a G protein-coupled receptor NlA42 in the brown planthopper Nilaparvata lugens

The neuropeptide elevenin and similar neuropeptide precursors are common in some invertebrates but their physiological function in most species has not been explored. The brown planthopper, Nilaparvata lugens (Stål) has an elevenin-like peptide and a G protein-coupled receptor (GPCR) NlA42 that is homologous to the elevenin receptor of the annelid Platynereis dumerilii. RNA interference (RNAi)-mediated knockdown of either Nl-elevenin or the NlA42 gene resulted in cuticle melanization. Ion transport peptide (ITP) also induces melanization, but unlike ITP, knockdown of NlElevenin and NlA42 did not have any effect on wing expansion or activity after eclosion. In wild condition macropterous individuals show a darker body color when compared with brachypterous individuals, but RNAi experiments suggest that insulin-signaling and Nl-elevenin signaling regulate wing morph and body color independently. NlElevenin was predominantly expressed in the brain while NlA42 was highly expressed in the abdominal integument and brain. A signal Calcium assays using aequorin indicated that NlA42 heterologously expressed in HEK293 cells exhibited responses to synthetic Nl-elevenin peptide from concentrations as low as 10−9M. These results suggest that neuropeptide Nl-elevenin is involved in the regulation of melanization through its receptor NlA42. This is the first report of a physiological function for elevenin-like peptides in insects.

Biased dispersal of Metrioptera bicolor, a wing dimorphic bush-cricket.

In the highly fragmented landscape of central Europe, dispersal is of particular importance as it determines the long-term survival of animal populations. Dispersal not only secures the recolonization of patches where populations went extinct, it may also rescue small populations and thus prevent local extinction events. As dispersal involves different individual fitness costs, the decision to disperse should not be random but context-dependent and often will be biased toward a certain group of individuals (e.g., sex- and wing morph-biased dispersal). Although biased dispersal has far-reaching consequences for animal populations, immediate studies of sex- and wing morph-biased dispersal in orthopterans are very rare. Here, we used a combined approach of morphological and genetic analyses to investigate biased dispersal of Metrioptera bicolor, a wing dimorphic bush-cricket. Our results clearly show wing morph-biased dispersal for both sexes of M. bicolor. In addition, we found sex-biased dispersal for macropterous individuals, but not for micropters. Both, morphological and genetic data, favor macropterous males as dispersal unit of this bush-cricket species. To get an idea of the flight ability of M. bicolor, we compared our morphological data with that of Locusta migratoria and Schistocerca gregaria, which are very good flyers. Based on our morphological data, we suggest a good flight ability for macropters of M. bicolor, although flying individuals of this species are seldom observed.

To fly or not to fly: Factors influencing the flight capacity of carabid beetles (Coleoptera: Carabidae)

This review considers factors affecting the flight capacity of carabid beetles and the implications of flight for carabids. Studies from the Dutch polders in particular show that young populations of carabids consist predominantly of macropterous species and macropterous individuals of wing-dimorphic species. Also populations of wing-dimorphic carabid species at the periphery of their geographical range contain high proportions of macropterous individuals. However, studies from Baltic archipelagos show that older populations of even highly isolated island habitats contain considerable proportions of brachypterous species and individuals. This suggests that macroptery is primarily an adaptation for dispersal and that there exists a mechanism for subsequently reducing the ratio of macropterous to brachypterous species under stable conditions, due to the competitive advantage of brachyptery. Populations in isolated habitats, such as islands and mountains, have high proportions of brachypterous species. Many macropterous species do not possess functional flight muscles. Species of unstable habitats, such as tree canopies and wet habitats, are mostly macropterous. Brachypterous species tend to disappear from disturbed habitats. There is uncertainty regarding the extent to which carabid dispersal is directed and how much passive. Both Den Boer and Lindroth recognized that mostly macropterous individuals of macropterous and wing-dimorphic species disperse and found new populations, after which brachyptery tends to rapidly appear and proliferate in the newly founded population. It is most likely that the allele for brachyptery would arrive via the dispersal of gravid females which had mated with brachypterous males prior to emigration. Whilst many studies consider wing morphology traits of carabid beetles to be species-specific and permanent, a number of studies have shown that the oogenesis flight syndrome, whereby females undertake migration and subsequently lose their flight muscles by histolysis before eventually regenerating them after reproducing, has been reported for a growing number of carabid species. Wing morphology of carabid beetles clearly offers strong potential for the study of population dynamics. This field of study flourished during the 1940's to the late 1980's. Whilst a considerable amount of valuable research has been performed and published, the topic clearly holds considerable potential for future study.

The Effect of Combinations of Food Insects for Continuous Rearing of the Wing Polymorphic Water Strider Limnogonus Fossarum fossarum (Hemiptera: Gerridae).

The water strider Limnogonus fossarum fossarum (F.) (Hemiptera: Gerridae) shows a macropterous, micropterous, and apterous polymorphism. Although a long photoperiod condition induces winged morphs, preliminary studies have revealed that crossing between winged morphs increased the proportion of macropterous individuals, suggesting that the genetic factors also affect wing-morph determination in this species. Assessing the genetic backgrounds of wing polymorphism requires constant and repeatable methods for rearing. This study attempts to establish a continuous rearing method for L. f. fossarum under constant diet conditions. Initially, we maintain the water striders with two Drosophila species as a food, but viability until adulthood is less than 20%. We then add the storage pest Plodia interpunctella (Hübner), which are readily reared in the laboratory, to the diets. As a result, nymphs fed on P. interpunctella (even only until the second instar) show significantly higher viability and shorter developmental period than nymphs fed on Drosophila alone. Moreover, feeding on D. melanogaster (Meigen) reared on cholesterol-enriched medium instead of a normal medium significantly increases viability in the next generation. This means that only the two food-insect species are enough for establishing a substantial number of individuals in segregating generations (F2 and backcross), limiting DNA and RNA contaminations from food insects with genome information. Thus, the present rearing method opens the way to elucidating the genetic backgrounds of the wing polymorphism in L. f. fossarum.

Can body traits, other than wings, reflect the flight ability of Triatominae bugs?

Insects of the subfamily Triatominae are vectors of Trypanosoma cruzi , the Chagas disease parasite, and their flying behavior has epidemiological importance. The flying capacity is strikingly different across and within Triatominae species, as well as between sexes or individuals. Many Triatoma infestans individuals have wings but no flying muscles. In other Triatominae species, no clear relationships were found between wing length and flying behavior. If wing presence or size is not reflective of the flying behavior, which other parts of the body could be considered as reliable markers of this important function? The genus Mepraia has exceptional characteristics with invariably wingless females and wingless or winged males. We calculated the porous surface exposed to odorant molecules to estimate the olfactory capacity of Mepraia spinolai . The head shape and thorax size were estimated using the geometric morphometric approach and traditional morphometric techniques, respectively. Alary polymorphism in M. spinolai was significantly associated with consistent modification of the thorax size, head shape, and notable change in the estimated olfactory capacity. The macropterous individuals had a larger olfactory surface and thorax size and significantly different head shape compared to those of the micropterous individuals. We concluded that these structural changes could be associated with the flying potential of Triatominae. Thus, morphological attributes not found on wings could help determine the likely flying potential of the bugs.

Analysis of the Classical Model of Juvenile Hormone Control of Wing Polymorphism in the CricketVelarifictorus aspersus(Orthoptera: Gryllidae)

The classical model of juvenile hormone (JH)-mediated wing polymorphism was proposed in the early 1960s, and numerous studies have tested this model using exogenous hormone treatment. However, this indirect method may yield misleading results, necessitating direct quantification of JH titers in insects. In this study, the effects of JH application on wing development and comparisons of hemolymph JH titers between presumptive long-winged (LW) and short-winged (SW) nymphs in the cricket Velarifictorus aspersus (Walker) are investigated. The results show that treatment of presumptive LW nymphs with high-dose JH III significantly decreases the percentage of macropterous individuals during the penultimate and first half of the last stadia, indicating that exogenous JH III can suppress wing development in V. aspersus and that the last two stadia are critical periods for wing determination. However, application of precocene to presumptive SW nymphs does not induce macropterizing effects, and JH III titers are not significantly higher in presumptive SW females than in presumptive LW females during the critical period of wing development. Therefore, this model may not be applicable to this species and the brachypterizing effects associated with JH application may be induced by affecting other innate factors rather than by direct JH titers in hemolymph.

Contrasting patterns of macroptery in Roesel’s bush cricketMetrioptera roeselii(Orthoptera, Ensifera)

We studied the wing dimorphism in Roesel's bush cricket populations. A total of 410 individuals (77 macropterous and 333 brachypterous) were sampled in seven sites. We found a high frequency (≤ 53%) of macropterous individuals in some meadows surrounded by forests. We measured the body weight, thorax weight, and abdomen weight in connection with macroptery vs brachyptery. We could find a positive correlation between macroptery and thorax weight. The abdomen weight of females showed high individual variation; thus the supposed trade-off between macroptery and lower fertility of females was not supported.

Temperature-dependent wing dimorphism in a Japanese strain of tobacco thrips, Frankliniella fusca (Thysanoptera: Thripidae)

A Japanese strain of Frankliniella fusca (Hinds) was reared under 4 temperature and two photoperiodic conditions on leaves of green bean. On the basis of the ratio of fore wing length to head width (RWL) of adult thrips we defined individuals with RWL above 3.7 as macropterous forms and those with RWL below 3.5 as brachypterous forms. Percentages of macropterous individuals among females were 0 % at 18 °C, 10.6 % at 22.5 °C, 21.8 % at 25 °C, and 77.5 % at 27.5 °C, under 15L–9D. The proportion of macropters among females developing under 15L–9D was no different from that among those developing under 10L–14D. These results indicate that photoperiod does not affect wing form, and suggest that the proportion of macropterous females increases with temperature. Although development time from hatching to adult eclosion, adult pre-oviposition period, adult head width, adult longevity, total fecundity, and fecundity schedule were compared between macropterous and brachypterous females developing at 25 °C and 15L–9D, these traits were not significantly different between the wing forms. Males of this experimental strain were all brachypterous.

Wing-dimorphism and population expansion of Pterostichus melanarius (Illiger, 1798) at small and large scales in central Alberta, Canada (Coleoptera, Carabidae, Pterostichini)

A study spanning ten years revealed changes in wing-morph ratios corroborating the hypothesis that the wing-dimorphic introduced carabid, Pterostichus melanarius Ill.,is spreading through flight, from the city of Edmonton, Canada and establishing populations in natural aspen forest of more rural areas 45-50 km to the East. Comparison of wing-morph ratios between Pterostichus melanarius and the native wing dimorphic species Agonum retractum LeConte suggests that the spatial variation in ratios for Pterostichus melanarius does not reflect underlying environmental variation, but instead the action of selective forces on this wing-dimorphic species. About ten years after its earliest detection in some rural sites the frequency of macropterous individuals in Pterostichus melanarius has decreased c. five-fold, but it is still above the level seen in European populations in which the two wing-morphs are thought to exist in equilibrium. Pterostichus melanarius is expanding its range in native aspen forest much faster than three other introduced species Clivina fossor L.), Carabus granulatus O.F. Müllerand Clivina fossor L also encountered in this study. The two Carabus species are flightless, but Carabus fossor can be dimorphic. Although these four non-native ground beetle species comprise >85% of the carabids collected at sites in urban Edmonton, activity-density of native carabids was similar across the urban-rural gradient, suggesting little direct impact of introduced species on the local abundance of native species. In a second study conducted at a smaller scale near George Lake, Alberta, macropterous individuals of Pterostichus melanarius have penetrated furthest and most rapidly into native aspen forest. Furthermore, the percentage of micropterous individuals has increased markedly in areas first colonized a decade previously. Overall, these studies support the idea that macropterous beetles in wing-d dimorphic species are important vanguards for early colonization of unexploited territory, but that flightless individuals replace the flying morph relatively rapidly once populations are established.

Effect of population density on the development of Mesovelia furcata (Mesoveliidae), Microvelia reticulata and Velia caprai (Veliidae) (Heteroptera: Gerromorpha)

Population density during nymphal development affects body size, developmental rate and wing polymorphism in semiaquatic bugs. Nymphs from crowded habitats grow faster and thus gain an advantage in the later stadia. Rapid development results in smaller body size in several gerrids. Macropterous adults develop more frequently at high population densities in most species, which enables the bugs to leave crowded habitats. Three European widespread species Mesovelia furcata Mulsant & Rey, 1852 (Mesoveliidae), Microvelia reticulata Burmeister, 1835 and Velia caprai Tamanini, 1947 (Veliidae) were reared individually and simultaneously either at a low or high population density. Duration of postembryonic development, wing morph, body size and length of distal oocyte in females were recorded. High population density accelerates development in Mesovelia furcata and Microvelia reticulata. However, there was no trade-off between developmental rate and body size. Accelerated development without a decrease in body size was probably because maturation was delayed. Individually reared nymphs developed faster than nymphs from communal cohorts. No long-winged Microvelia reticulata specimen developed in any treatment. However, more macropterous individuals developed in high-density treatments in Mesovelia furcata (significant) and Velia caprai (not significant). All the nymphs of the species that were reared individually developed into apterous adults. The results suggest that population density strongly influences the life history of semiaquatic bugs. However, the only commonly shared response seems to be an increase in developmental rate when reared at high population densities. Other traits such as wing dimorphism, body size and rate of oogenesis differ at the species level.

Grass Thrips (Anaphothrips obscurus) (Thysanoptera: Thripidae) Population Dynamics and Sampling Method Comparison in Timothy

Sampling studies were conducted on grass thrips, Anaphothrips obscurus (Müller) (Thysanoptera: Thripidae), in timothy, Phleum pratense L. These studies were used to compare the occurrence of brachypterous and macropterous thrips across sampling methods, seasons, and time of day. Information about the population dynamics of this thrips was also revealed. Three absolute and two relative methods were tested at three different dates within a season and three different daily times during four harvest periods. Thrips were counted and different phenotypes were recorded from one of the absolute methods. Absolute methods were the most similar to one another over time of day and within seasonal dates. Relative methods varied in assessing thrips population dynamics over time of day and within seasonal dates. Based on thrips collected from the plant and sticky card counts, macropterous individuals increased in the spring and summer. Thrips aerially dispersed in the summer. An absolute method, the beat cup method (rapping timothy inside a plastic cup), was among the least variable sampling methods and was faster than direct observations. These findings parallel other studies, documenting the commonality of diel and diurnal effects on sampled arthropod abundance and the seasonal effects on population abundance and structure. These studies also demonstrate that estimated population abundance can be markedly affected by temporal patterns as well as shifting adult phenotypes.

Experimental evidence for density-determined wing dimorphism in two bush-crickets (Ensifera: Tettigoniidae)

Macroptery is common in many species of Orthoptera, but the causes are still discussed. Besides the assumption that macroptery is genetically determined, there is evidence that wing dimorphism is induced by environmental factors, particularly population density. However, most of the research is on pest species. In contrast, knowledge of wing dimorphism in species that occur at low population densites is still poor. Our study aims to test how density actually affects macroptery. As model organisms we chose two bush-cricket species of the genus Metrioptera (Ensifera: Tettigoniidae): While long-winged M. roeselii (Hagenbach, 1822) occur regularly, macropterous M. brachyptera (Linnaeus, 1761) are rare and are never observed outside their mating habitat. Nymphs of populations from the range core of both species (340 individuals each) were reared in groups of three and six individuals per 500 cm3 box, and individually. Our analyses revealed that development of macropters was mainly affected by the initial rearing densities. Compared with those reared individually the number of macropters was significantly higher among individuals reared at medium and high densities. The percentage of macropterous individuals was about twice as high in M. brachyptera as in M. roeselii, and the development of macropters significantly differed between the two species. These findings lead to the conclusion that macropterism is mainly influenced by density stress in both bush-crickets. Genetically determined wing dimorphism is unlikely, otherwise the observed high numbers of long-winged individuals of M. brachyptera, which are very rare under natural conditions, would never have developed in the laboratory. Macropterous M. brachyptera may rarely be found in the field, but we argue that this is due to low natural densities and, accordingly, to rare exposure to density stress.

Correlated traits for dispersal pattern: Terrestrial movement of the water cricket Velia caprai (Heteroptera: Gerromorpha: Veliidae)

Macropterous individuals of wing polymorphic semiaquatic bugs (Heteroptera: Gerromorpha) usually occur at a high fre- quency if there is a need to leave an unfavorable habitat or in a generation migrating to/from an overwintering site. Velia caprai (Veliidae) is usually found in unpredictable habitats, but the macropterous morph is rare. Laboratory, mesocosm and field experi- ments were used to test the hypothesis that individuals of this species migrate by walking rather than by flight. Laboratory experi- ments that focused on the development of macropterous morph under conditions that usually stimulate the development of this morph in water striders were unsuccessful. A high temperature shortened the duration of nymphal development, but no winged specimens of Velia caprai developed in the laboratory when reared under either high or low temperatures, long or short photoperiods or on the surface of water or wet filter paper. Mesocosm experiments with apterous adults revealed they are able to walk on land. Both the males and females dispersed by walking in semi-natural conditions. Long-term field experiments using mark and recapture confirmed that this species can disperse by walking. Apterous individuals can compensate for downstream drift by upstream terres- trial migration and colonize newly established pools and ditches even several tens of meters from source sites. The development of a macropterous morph in response to environmental factors is replaced by terrestrial dispersal in V. caprai.

Macropterism of Roesel's BushcricketMetrioptera roeseliiin Relation to Climate Change and Landscape Structure in Eastern England

Abstract There has been a considerable range expansion for Roesel's bushcricket Metrioptera roeselii in Essex since 1980, and it is often assumed that the macropterous (long-winged) form (f. diluta) has played an important role. A systematic study of the occurrence and distribution of this bushcricket in the county shows that this range expansion has corresponded with a significant increase in air temperature and the availability of tall grassland on farmland, due to the introduction of set-aside and agri-environment schemes such as Countryside Stewardship. These tall grasslands are particularly important for M. roeselii in areas of the county (e.g., the northwest) where hedgerow removal has been severe since the 1940s. This study indicates that the previous year's air temperature may be the most crucial climatic determinant of macroptery, hot weather leading to successful breeding and high population densities in the following year. These populations may then produce macropterous individuals in response ...