Comparative Genetic Structure of the Threatened Tenebrionid Beetle Oplocephala haemorrhoidalis and its Common Relative Bolitophagus reticulatus

We used RAPD and allozyme genetic markers to compare the genetic structures of a threatened saproxylic tenebrionid beetle, Oplocephala haemorrhoidalis, and its common relative (different subfamilies), Bolitophagus reticulatus, to evaluate the relative importance of habitat fragmentation on the occurrence of the two species. O. haemorrhoidalis showed significantly higher levels of genetic differentiation between sites than B. reticulatus for both types of genetic marker. Patterns of isolation by distance were consistent with (B. reticulatus) or close to (O. haemorrhoidalis) theoretical expectations for equilibrium between gene flow and genetic drift. For O. haemorrhoidalis, the RAPD-patterns also showed a steeper increase in isolation by distance where geographic distances were small than at larger distances. This suggests that gene flow between the populations of O. haemorrhoidalis has declined as an effect of recent habitat fragmentation and is probably relatively restricted at present. For B. reticulatus, levels of genetic differentiation were low, suggesting that B. reticulatus readily moves over large areas. Genetic variability was not low in either species. Genetic differentiation among and relatedness within fruiting bodies varied substantially within sites for both species. This variation was probably due to founder events: when levels of relatedness were close to zero, genetic differentiation was also low.     

The saproxylic beetle Bolitophagus reticulatus: its frequency in managed forests, attraction to volatiles and flight period

Reduction in amount of dead trees in Scandinavian forests due to intensive forest management has aroused interest in the requirements of saproxylic (wood-living) species. Much attention has been focused on Bolitophagus reticulatus , a tenebrionid beetle that lives on polypore fruiting bodies of Fomes fomentarius . Although earlier studies have suggested that the species has limited dispersal abilities, the beetle is abundant and widely distributed in Swedish forests. To resolve this paradox we conducted a series of field experiments. Firstly, the frequency of the species was found to be similar in six forest stands with a low density of fruiting bodies and six stands with a high density. Secondly, flying individuals were caught in window traps placed in all of eight randomly chosen, well-managed pine stands. Thirdly, we tested volatiles that flying beetles may use to find hosts by baiting window traps. We found strong attractions to ethanol and to a combination of ethanol and fruiting body. The dispersal period was almost entirely restricted to one week during the summer. Our results suggest that B. reticulatus is distributed wherever the host occurs. Long distance dispersal of B. reticulatus is difficult to observe, but appears to be effective when it does occur. Previously observed patchy distribution patterns of the species are probably due to short-distance movements being more frequent than long-distance movements. A general conclusion is that interpretations based on mark-recapture data and indirect measures of substrate and beetle occurrences that claims limited dispersal should be treated with caution.     

Reproductive cost of flight capability: a comparison of life history traits in wing dimorphic planthoppers

Abstract. 1. Reproductive costs associated with flight capability were evaluated in the wing dimorphic planthopper, Prokelisia dolus Wilson, by comparing the life history of traits of winged (macropterous) and flightless (brachypterous) females under controlled laboratory conditions.
2. Macropters with large thoraces and fully developed wings maintain a greater investment in flight apparatus than brachypters with small thoraces and reduced wings.
3. Associated with greater flight capability in the macropter of P.dolus are shorter adult life, decreased total fecundity, and delayed age at first reproduction compared to brachypterous females.
4. Under field conditions where mortality is high, the difference in realized fecundity between the two wing forms living on similar resources is further exaggerated with the brachypter having the greater advantage.
5. When the life history traits of the wing forms of P. dolus are compared with traits for nine other species of planthoppers, two similarities emerge. First, the preoviposition period of the macropterous wing form is always longer than that for the brachypter resulting in a reproductive delay. Second, most studies show that macropters are less fecund than brachypters.
6. There is no general tendency among planthopper species for macropterous adults to live fewer days or develop more slowly as nymphs compared to their flightless counterparts.
7. The reproductive delay and reduced fecundity of the volent wing form of planthoppers supports the notion that flight capability is costly and that phenotypic trade-offs between flight and reproduction exist.     

Investigations of the oogenesis-flight syndrome inAnthonomus grandis (Coleoptera: Curculionidae) using tethered flight tests

This paper investigates the relationship between oogenesis and flight duration and the use of tethered flight as an indicator of tendency to migrate inAnthonomus grandis grandis Boheman (Coleoptera: Curculionidae), the boll weevil. When boll weevils were flown to exhaustion in tethered flight tests, many flew between 2 and 3 h, with several flying more than 4 h. To test the validity of the tethered flight test as an indicator of tendency to migrate, comparisons of mean flight duration were made between boll weevils trapped in pheromone traps far from any cultivated cotton and those trapped at the edge of heavily infested, flowering cotton fields. There was a significant difference in mean flight time between the two groups, supporting the assumption that long-duration tethered flight in the laboratory reflects the tendency to make long-distance flights in the field. Groups of weevils of different ages were killed after flight testing, and the degree of ovarian development and fat body status were determined and related to duration of tethered flight. Insects with undeveloped or partially developed ovaries were the most likely to make long flights. Weevils with ovaries bearing chorionated eggs made very few long flights. Flight duration was positively correlated with degree of fat body development. In contrast, there were no significant differences in the degree of ovarian development with fat body status. We conclude from these experiments thatA. grandis grandis is capable of long-distance flight, that this species displays some behavioral and physiological characteristics typical of many insect migrants including an oogenesis-flight syndrome, and that a tethered flight test is an appropriate means of measuring migratory tendency in this species.     

Simultaneous monitoring of flight and oviposition of individual velvetbean caterpillar moths

ABSTRACT. A 'pivot' flight actograph was combined with a rolling oviposition surface to characterize the flight and oviposition behaviour of velvetbean caterpillar moths, Anticarsia gemmatalis Hubner. Tethered, caged control females laid significantly more eggs that those flown on the actograph. Mated females laid more eggs than unmated ones. However, mating did not affect longevity nor fight frequency and duration. Laboratory-reared and wild-type females also did not differ signficantly in longevity and flight. Both laboratory and wild mated females laid most of their eggs during the first 7 days whereas unmated ones delayed their oviposition. None of the female types produced a definite hourly, daily or lifetime pattern in flight frequency or duration. Of the 7672 recorded flights, about 3% were greater than 0.5 h. 'Long' flights (>0.5h) were made by some females before oviposition, as in colonization migration, but most interspersed flight with oviposition, as in extended search migration.     

Reproductive variation and adult size in two co-occurring grasshopper species

ABSTRACT. 1. Egg sizes and clutch sizes of the grasshoppers Chorthippus brunneus (Thunb.) and Myrmeleotettix maculatus (Thunb.) were compared among three years and among three sites less than 1.3 km apart. Relationships between these reproductive traits and date of egg laying, body size and body condition were sought.
2. M.maculatus , the smaller species, laid fewer but larger eggs; and only the eggs of this species showed significant differences between sites and years.
3. A negative correlation between egg size and number per clutch was evident between species and years, but generally not among sites and among individuals of a population.
4. However, a hidden negative correlation between egg size and number was uncovered within populations when the relationship was examined for females of a given mature weight.
5. Variation in the number of eggs per clutch was explained statistically by a positive relationship between female body weight and egg number. Also, both interpopulation and intrapopulation comparisons revealed that for M.maculatus , but not for C.brunneus , females with long hind femurs laid large eggs.     

Genetic and phenotypic variation for flight ability in the cactophilicDrosophila species,D. aldrichi andD. buzzatii

The flight ability ofDrosophila aldrichi (Patterson & Crow) andD. buzzatii (Patterson & Wheeler) using tethered flights, was measured with respect to age-related changes, genetic variation and adult body size variation induced by rearing at different larval densities.Drosophila buzzatii flew for much longer thanD. aldrichi, especially females, but age-related changes in flight duration were significant only forD. aldrichi. Effects of body size on flight ability were significant inD. buzzatii, but not inD. aldrichi. InD. buzzatii, there was a significant genotype-environment interaction (larval density × line) for flight duration, with short and average flight duration isofemale lines showing longer flights, but a long flight duration line shorter flights as body size decreased (i.e., as larval density increased). Heritability estimates for flight duration were similar in the two species, but flight duration showed no significant genetic correlations with developmental time, body size or wing dimensions (except for one wing dimension inD. buzzatii). Although not significantly different between the species, heritabilities for life-history traits (adult size and developmental time) showed contrasting patterns — with higher heritability for body size (body weight and thorax length) inD. buzzatii, and higher for developmental time inD. aldrichi. In agreement with limited previous field evidence,D. buzzatii is better adapted for colonization than isD. aldrichi.     

Juvenile hormone titer and morph-specific reproduction in the wing-polymorphic cricket,Gryllus firmus

Juvenile hormone titers and reproductive characteristics were measured in adult wing and flight-muscle morphs of the wing-polymorphic cricket, Gryllus firmus, during the first week of adulthood. This species has three morphs: one flight capable morph with fully-developed wings and fully-developed flight muscles [LW(F)], one flightless morph with fully-developed wings and histolyzed (non-functional) flight muscles [LW(H)], and another flightless morph with underdeveloped (short) wings and underdeveloped flight muscles (SW). Both flightless morphs [LW(H) and SW] had larger ovaries which contained a greater number of postvitellogenic eggs compared with the flight capable [LW(F)] morph. The juvenile hormone titer was significantly higher in SW compared with LW(F) females on days 3-7 of adulthood. On these days, the JH titer also was significantly higher in the other flightless morph, LW(H), compared with flight-capable [LW(F)] females as determined by one statistical test, but did not differ significantly by another test. The JH titer was positively correlated with ovarian mass or terminal oocyte length, but not with the number of post-vitellogenic eggs. This study is the first direct comparison of juvenile hormone titers in adult wing morphs of a wing-polymorphic insect. Results indicate that an elevated juvenile hormone titer may be at least partly responsible for one of the most distinctive features of wing-polymorphic species, the increased early fecundity of flightless females.     

Significance of spring migration and flexibility in flight-muscle histolysis in waterstriders (Heteroptera, Gerridae)

Abstract. 1. Individuals of long-winged waterstrider (Gerridae) species were found in spring far from their breeding habitats, which indicates that they fly before reproduction.
2. Field samples and laboratory studies show that once they return to their breeding sites, many individuals of three waterstrider species ( Gerris odontogaster (Zett.), Gerris lacustris (L.) and Limnoporus rufoscutellatus (Lat.)) histolyse wing muscles and lose flight ability during their reproductive period.
3. The extent of flight-muscle histolysis varies with environmental factors. Food scarcity affects flight-muscle histolysis in G.odontogaster females. In G.Lacustris , flight-muscle histolysis was more common in the laboratory than in the field samples. Proportionately more females than males lost their flight ability by the end of the reproductive period.
4. Flight ability had direct costs in reproductive potential with (non-flyer) females, which histolysed their flight muscles, laying more eggs than (flyer) females, which maintained flight ability. This was also the case during food scarcity. Non-flyer males of G.odontogaster survived longer than flyer males.
5. Spring migration was distinguished from dispersal during the reproductive period, because these flights serve different functions. Flight-muscle histolysis of females during reproduction is a qualitative reproductive option, with a trade-off between dispersal ability and reproductive potential. Ability to change reproductive behaviour depending on environmental conditions increases an individual's ability to cope with a large variety of habitats.     

Flight threshold, wing muscle histolysis, and alary polymorphism: correlated traits for dispersal tendency in the Gerridae

ABSTRACT. 1. This paper tests the hypothesis that selection for dispersal ability within a species influences not only the occurrence and extent of wing reduction but also the tendency or ability of the macropterous individuals to fly.
2. Flight thresholds of four species of waterstriders (Hemiptera; Gerridae) were assessed using a tethered flight technique. The species tested varied from monomorphic macropterous ( Limnoporus dissortis Drake and Harris), through seasonally polymorphic ( Gerris comatus Drake and Hottes and G. buenoi Kirkaldy), to primarily apterous ( G.remigis Say).
3. Condition of the indirect, mesothoracic flight muscles, and presence or absence of mature or developing eggs (for females) were determined by dissection of all individuals immediately following flight testing. Only individuals with normal muscles were included in the analysis of flight thresholds.
4. Comparisons among species revealed that average flight threshold and extent of flight muscle histolysis were negatively associated with the proportion of macropterous individuals. Wing reduction was also associated with significant seasonal variation in flight threshold, particularly among females.
5. These results support our initial hypothesis, and further indicate that, within the Gerridae, dispersal tendency depends not only on the proportion of macropters but also on the dispersal capability of the macropterous individuals.     

To fly or not to fly: response of water striders to drying out of habitat

Abstract .1. Adults of Aquarius paludum inhabit both temporary and permanent water surfaces; Gerris latiabdominis lives only in temporary habitats. To clarify whether adults of both species stay in position or fly when habitats dry up, overwintered adults of A. paludum and G. latiabdominis collected in spring were reared under one of the following four conditions: (A) on water with sufficient food, (B) on water, starved, (C) on wet paper with sufficient food, (D) on wet paper, starved. All rearings were at LD 15.5:8.5 h, 20 ± 2 °C, resembling natural conditions for April to June.
2. Females of A. paludum in group C had lower fecundity than the control group A and some stopped laying eggs. When a water surface was restored, females that had entered reproductive diapause began to lay eggs again. In contrast, females of G. latiabdominis continued to lay eggs even when reared on damp paper.
3. Adults of A. paludum lived longer and adopted diapause posture with high frequency when starved and reared without a water surface. There were, however, no significant differences in the longevity or in the number of adults showing diapause posture between groups A and D of G. latiabdominis.
4. Females of A. paludum collected in the middle of May had more mature oocytes (mean: 20.8) than females of G. latiabdominis (mean: 8.0), and most had histolysed their indirect flight muscles; most females of G. latiabdominis had retained their flight muscles and flew readily.
5. When water surfaces dry, with food shortage, adults of A. paludum may survive in place for a relatively long time until the water surface returns. Adults of G. latiabdominis may fly to other water surfaces and reproduce without delay.     

Effect of sex,age and morphological traits on tethered flight of Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) at different temperatures

The oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), is a pest of fruit and vegetable production that has become established in 42 countries in Africa after its first detection in 2003 in Kenya. It is likely that this rapid expansion is partly due to the reported strong capacity for flight by the pest. This study investigated the tethered flight performance of B. dorsalis over a range of constant temperatures in relation to sex and age. Tethered flight of unmated B. dorsalis aged 3, 10 and 21 days was recorded for 1 h using a computerized flight mill at temperatures of 12, 16, 20, 24, 28, 32 and 36 °C. Variations in fly morphology were observed as they aged. Body mass and wing loading increased with age, whereas wing length and wing area reduced as flies aged. Females had slightly larger wings than males but were not significantly heavier. The longest total distance flown by B. dorsalis in 1 h was 1559.58 m. Frequent short, fast flights were recorded at 12 and 36 °C, but long-distance flight was optimal between 20 and 24 °C. Young flies tended to have shorter flight bouts than older flies, which was associated with them flying shorter distances. Heavier flies with greater wing loading flew further than lighter flies. Flight distances recorded on flight mills approximated those recorded in the field, and tethered flight patterns suggest a need to factor temperature into the interpretation of trap captures.     

Ecomorphology of the wheatears (genus Oenanthe)

We used measurements of museum skins to assess morphological differences between the 22 currently recognized species of wheatear and to identify correlations between morphological features, behavioural traits and degrees of sympatry between species. Ground-dwelling species of steppe-like habitats have long tarsi, long claws and short tails; some are migratory and have long pointed wings and non-emarginated primaries ( O. isabellina and O. oenanthe ), while others are sedentary and have more rounded and slotted wings ( O. bottae , O. heuglini and O. pileata ). Vegetation-tolerant species ( O. pleschanka , O. hispanica , O. cypriaca and O. deserti ) have relatively long tails, short tarsi, long middle toes and long claws. The rock-dwelling species have short tarsi, long toes and short claws; they can be either relatively heavy ( O. leucura and O. monticola ) or light, like the wheatears inhabiting the most arid areas ( O. monacha , O. leucopyga and O. alboniger ). Although sedentary, the latter show intermediate characteristics between sedentary and migratory species, having relatively pointed wings with non-emarginated primaries. Together with their low wing-loadings, these traits may be related to the scarcity of resources in their habitats, which obliges them to make frequent and long flights. The clear morphological differentiation between wheatear species appears to be mainly related to their migratory and foraging habits, but seems to bear no relation to their degree of sympatry.     

Wing and flight muscle polymorphism in a lygaeid bug, Horvathiolus gibbicollis: determinants and life history consequences

ABSTRACT.

• 1 Horvathiolus gibbicollis (Costa), a ground-living seed-feeding bug of the mediterranean region, has two wing morphs. In macrop-terous bugs both pairs of wings are fully developed. In brachypterous ones forewings are reduced to about two-thirds and hindwings to less than a third of their length in macropters.
• 2 Each morph bred true with regard to wing length when reared under variable density, food and temperature conditions for several generations.
• 3 All F₁ offspring between crosses of the two morphs were brachypterous. In F₂ approximately 25% were macropters and 75% brachypters implying monogenic control of wingform.
• 4 Flight muscles in macropters vary from fully developed to totally reduced. This variation is determined by environmental conditions during adult life. Most young adult bugs have flight muscles, and totally starved or unmated bugs retain their flight muscles. Fed and mated females histolyse flight muscles as they start laying eggs, while most males of the same group retain their muscles.
• 5 Brachypterous bugs have a smaller thorax and larger abdomen than macropterous ones.
• 6 Brachypterous bugs reach adulthood slightly before macropterous ones, and they have a distinctly shorter adult preoviposition period.
• 7 Lifetime egg production does not differ significantly between the two wing morphs. However, the temporal pattern of egg laying is different in the two morphs. The m_x-curve of macropters starts later, then attains a higher peak and finally decreases faster than that of brachypters.
• 8 Initially, macropters lay smaller eggs than brachypters, but egg volume increases with age in macropters and eventually approaches that of brachypters.
• 9 The initial increase in reproductive effort (egg volumexegg number) of macropters is concomitant with wing muscle histolysis and the mobilization of thorax space for reproduction.
• 10 Adult survival rate does not differ between the morphs.

     

Relationship between body size and flying-related structures in Neotropical social wasps (Polistinae,Vespidae, Hymenoptera)

Body size influences wing shape and associated muscles in flying animals which is a conspicuous phenomenon in insects, given their wide range in body size. Despite the significance of this, to date, no detailed study has been conducted across a group of species with similar biology allowing a look at specific relationship between body size and flying structures. Neotropical social vespids are a model group to study this problem as they are strong predators that rely heavily on flight while exhibiting a wide range in body size. In this paper we describe the variation in both wing shape, as wing planform, and mesosoma muscle size along the body size gradient of the Neotropical social wasps and discuss the potential factors affecting these changes. Analyses of 56 species were conducted using geometric morphometrics for the wings and lineal morphometrics for the body; independent contrast method regressions were used to correct for the phylogenetic effect. Smaller vespid species exhibit rounded wings, veins that are more concentrated in the proximal region, larger stigmata and the mesosoma is proportionally larger than in larger species. Meanwhile, larger species have more elongated wings, more distally extended venation, smaller stigmata and a proportionally smaller mesosoma. The differences in wing shape and other traits could be related to differences in flight demands caused by smaller and larger body sizes. Species around the extremes of body size distribution may invest more in flight muscle mass than species of intermediate sizes.     

Winged leaf-cutting ants on nuptial flights used as transport by Attacobius spiders for dispersal

Abstract.  1. Sexuals of a leaf-cutting ant, Atta bisphaerica Forel, left their nest for nuptial flights in October to December.
2. When leaving a nest, 53 of the 479 winged sexuals (or alates) observed (11.1%) carried up to three inquiline spiders of Attacobius luederwaldti .
3. Spiders exclusively selected winged sexuals, not workers, and preferred females, indicating their expectation of the stronger flight ability of females. Neither these sexuals nor workers that appeared out of the nest on flight days attempted to remove or attack spiders on the body of alates.
4. New qucens landing from their nuptial flight did not carry spiders, indicating that the spiders had left the ants in the sky to be dispersed by wind.
5. No spiders were found in more than 100 incipient nests, which were estimated to be 2–3 months old. This suggests that the spiders jumped off the alate during mid-flight and dispersed on the wind to inhabit larger nests.     

Evolutionary relationships among food habit, loss of flight, and reproductive traits: life-history evolution in the Silphinae (Coleoptera: Silphidae)

Flightlessness in insects is generally thought to have evolved due to changes in habitat environment or habitat isolation. Loss of flight may have changed reproductive traits in insects, but very few attempts have been made to assess evolutionary relationships between flight and reproductive traits in a group of related species. We elucidated the evolutionary history of flight loss and its relationship to evolution in food habit, relative reproductive investment, and egg size in the Silphinae (Coleoptera: Silphidae). Most flight-capable species in this group feed primarily on vertebrate carcasses, whereas flightless or flight-dimorphic species feed primarily on soil invertebrates. Ancestral state reconstruction based on our newly constructed molecular phylogenetic tree implied that flight muscle degeneration occurred twice in association with food habit changes from necrophagy to predatory, suggesting that flight loss could evolve independently from changes in the environmental circumstances per se. We found that total egg production increased with flight loss. We also found that egg size increased with decreased egg number following food habit changes in the lineage leading to predaceous species, suggesting that selection for larger larvae intensified with the food habit change. This correlated evolution has shaped diverse life-history patterns among extant species of Silphinae.     

Survival and habitat preferences of adult Bolitophagus reticulatus

1. Data from a 4-year mark–recapture study of the fungivorous tenebrionid beetle Bolitophagus reticulatus at a locality in central Sweden and a trapping study of the species elsewhere in the same region are used to describe the survival and habitat preferences of the species.
2. The adult beetle was found to survive for up to three winters. A minimum estimate of the yearly survival rate was 0.20.
3. The beetle was found to occur preferentially on tree trunks that were either standing or lying but only touching the ground along a minor part of their length; that were relatively thick; and that carried many Fomes fomentarius sporocarps. In contrast to previous information for this species, the beetle was found to use living sporocarps to a large extent, and not only dead ones.
4. An experiment with beetles given a choice between living and dead fungus tissue indicated that pairs of one male and one female beetle preferred living fungus while single beetles preferred dead fungus.     

Analysis of two components of flight using recombinant inbred lines of Drosophila melanogaster

Complex activities require precise coordination of their components for successful action. The genetic basis underlying coordination of traits may range from relatively static pleiotropic associations to more flexible genetic associations that recombine in phenotypes under continuous selective modification by the environment. Successful flight in insects depends on the precise integration of numerous component physiological processes. Here we examine the genetic basis of two of its components, flight duration and rate. To study flight we created recombinant inbred populations from stocks of this laboratory known for their significantly longer duration flights. A heritable basis for these traits was found and determined to be positively correlated between sexes. Correlations of flight length with rate were negative within sexes, suggesting a trade-off, but were significant in males only. Composite interval mapping using the recombinant inbred (RI2) design was used to locate the QTLs for these traits and test for pleiotropy. Four QTLs affecting duration or wing beat rate were found on chromosomes II and III. Tests for pleiotropy showed some effects on traits of QTLs were common to both sexes while others were sex-specific. No QTL was pleiotropic for both traits, suggesting that correlations between flight duration and rate of wing beat are determined by a combination of linkage and environmental factors.     

Analysis of Maneuvering Flight of an Insect

Wing motion of a dragonfly in the maneuvering flight, which was measured by Wang et al. was investigated. Equations of motion for a maneuvering flight of an insect were derived. These equations were applied for analyzing the maneuvering flight. Inertial forces and moments acting on a body and wings were estimated by using these equations and the measured motions of the body and the wings. The results indicated the following characteristics of this flight: ( 1 ) The phase difference in flapping motion between the two fore wings and two hind wings, and the phase difference between the flapping motion and the feathering motion of the four wings are equal to those in a steady forward flight with the maximum efficiency. (2)The camber change and the feathering motion were mainly controlled by muscles at the wing bases.