Agonistic behaviour in final-instar larvae of Austrolestes colensonis (Odonata: Lestidae)

Abstract

The agonistic displays of Austrolestes colensonis larvae are described. A terminology is developed to classify larval agonistic displays in the family Lestidae.     

Feral sheep and cattle and royal albatrosses on Campbell Island; population trends and habitat changes

Abstract

Sheep farming on Campbell Island began in 1895 and ended in 1931. The sheep population peaked at 8500 in 1910; only 1000 feral sheep were counted in 1961, but by 1969 there were 3000. The island was divided with a fence in 1970 and the sheep on the northern half were shot. Sheep continued to increase south of the fence, from 2088 in 1969 to 2521 in 1971 and, after a decline to 2400 in 1976, to 2861 in 1977. Breeding pairs of royal albatrosses numbered 2278 in 1958, 4344 in 1969, 5336 in 1976, and 4906 in 1977 - the first time the breeding population of this normally biennial breeder had been counted in two consecutive years. The number of feral cattle decreased from 20 in 1971 to 11 in 1977. These population trends are discussed in the context of changes to the flora in grazed and stock-free areas.     

Isophlebiid dragonflies from the Late Mesozoic of eastern Transbaikalia (Odonata: Isophlebiidae)

Based on the study of more than 300 isophlebiid specimens from several Late Mesozoic sites in eastern Transbaikalia (Ukurei, Tergen’, Glushkovo, and Byankino formations), new genera and species are described: Xeta olovica, Dahurium draco, and Sinitsia sophiae. The insect-bearing deposits are dated Late Jurassic according to analysis of their odonatofauna.     

Identification of dragonflies (Odonata) as indicators of general species richness in boreal forest lakes

We argue the need to select indicator species on empirical data to avoid influence of personal opinions. To test an empirical selection process based on a nested subset matrix, we sampled partivoltine dragonfly larvae from 74 small lakes in central Sweden. A nestedness matrix was set up using the 'nestedness temperature calculator' program, selecting 11 species as potential indicators of species richness. These were tested against a known indicator species for water quality (the pool frog) and plant diversity through inventories and comparison to existing surveys of biological values ('rich' lakes vs. 'ordinary' lakes). We could only see a trend towards the pool frog occurring in dragonfly-rich lakes, but found a significant connection between the number of aquatic plants along the shore line and the number of dragonfly species present. A significantly higher number of indicators were encountered in lakes previously surveyed as 'rich' in plants than in lakes classified as 'ordinary'. Dragonfly species richness therefore appears to be positively associated with species richness of vascular plants. We propose nestedness matrices to be a good selecting tool for indicator species, particularly in groups where the biology of the species is not well known. However, it is important to define what such indicators really indicate.     

Flexible Mate Guarding Tactics in the Dragonfly Sympelrum Internum (Odonata: Libellulidae)

Mate guarding–a behaviour prevalent in odonates–is a post copulatory association during which males prevent females from re-mating. Some species use two forms of guarding: contact mate guarding, which is energetically costly but highly effective and non-contact mate guarding, which is less costly but less effective. This study aimed to determine if male Sympetrum internum (Odonata:Libellulidae) adjust the duration of contact mate guarding according to environmental, temporal and physiological factors. There was a significant interaction between male density and season on duration of contact mate guarding. Early in the season males increased the duration of contact guarding as the density of rivals increased. Later in the season males guarded mates longer irrespective of male density. Wind and temperature did not detectabiy alter the duration of contact mate guarding, suggesting that the trade-off between current and future reproductive success was more important than were physiological costs.     

Habitat characteristics and the distribution of Odonata in a lowland river catchment in eastern England

The influence of habitat characteristics on the distribution of larval and adult Odonata communities in a lowland river in eastern England was studied. There was a longitudinal distribution of Odonata, with larval assemblages being influenced directly by marginal flow velocity, biochemical oxygen demand (BOD) and phosphate concentrations and indirectly by shade and cover of floating vegetation. Adult populations responded directly to shade, reed cover, amenity-managed land use and bank height, and indirectly to BOD and ammonia concentrations. Distribution patterns were strongly associated with both natural changes along the river system and management impacts. River management practices locally disrupted the natural displacement of species along the river, but whilst some forms of human interference on river systems were beneficial to species richness, the effects on stenotopic species were disadvantageous. To conserve Odonata management emphasis should be on the maintenance of suitable conditions for river specialists.     

Influences on variation in territorial tenures of male white-faced dragonflies (Leucorrhinia intacta) (Odonata: Libellulidae)

Some individuals in species with extended periods of territorial occupancy may change territory locations within a single bout of territorial activity. Length of occupancy of mating territories among males in a local population of white-faced dragonflies (Leucorrhinia intacta) varied from more than 6 h to 15 min or less. Males with short tenures often established territories in several locations on the pond during a day. Several hypotheses have been proposed to explain shifting territorial sites rather than remaining in a single site during one bout of territoriality. We attempted to test the hypothesis that males shift to leave low-quality sites. Site quality may be affected by costs of defense in relation to intruder rate and the mating benefits of holding the territory. To test whether variation in these possible effects of benefits and costs of territoriality influenced tenure, we manipulated local quality of oviposition substrate and perch density. The quality of oviposition substrate, but not perch density, influenced both potential benefits and costs of territoriality. Female density was higher in areas with good substrate, but so were rates of males intruding into the territories, rates of chasing by territorial males, and local density of territorial males. More matings occurred in areas with good substrate, but among males with tenures of 15 min or more, mating success per male and tenure lengths did not differ statistically among treatments. Defense costs were low for all treatments and perhaps were not an important influence on tenure duration. Territorial males in this population probably adjusted local density to expected mating success by initial choice of site rather than by varying tenure length. Variation in tenure length at a site resulted, in part, from stochastic external factors, such as predation attempts.     

Pre-oviposition mate-guarding and mating behaviour of Argia vivida (Odonata: Coenagrionidae)

Abstract. 1. At Halcyon Hotsprings, British Columbia, Canada, male and female Argia vivida Hagen encountered to mate in two different ways.
2. In the morning (before 12.30 hours solar time), males basked at sunspots in the forest and darted out at passing females, attempting to take them in tandem (the first method of encounter).
3. If a male was successful, the pair engaged in a 31.3±4.8 min copulation followed by an hour of tandem flight before beginning oviposition.
4. As the day progressed, unmated males moved slowly toward the water and arrived at the water at about the same time as the earliest ovipositing pairs (1131±27.5 min solar time).
5. Males retained their grasp on their mates during oviposition (contact-guarding) but since some tandems separated during oviposition, non-tandem males at the water could capture recently released, gravid females (the second method of encounter).
6. The new pairs performed a brief copulation (10.2±3.38 min) and began ovipositing immediately thereafter.
7. Some females that avoided recapture attempted to oviposit unguarded.
8. We believe the long duration of morning copulations and period of tandem constitute a male strategy, which we call 'pre-oviposition guarding', to guard females until it is warm enough at the oviposition site for the females to begin ovipositing.
9. Separation of tandems during oviposition may be initiated by either member of the pair and we suggest that one benefit to a female of leaving a guarding mate is increased efficiency of oviposition when the intensity of male harassment is low.
10. The mating system of A. vivida thus comprises a series of complementary male and female mating behaviours.     

中国原(虫怱)科一新种和(虫怱)科一新种(蜻蜓目)

记述采自广东省原科1新种:华氏齿原Prodasineura huai,sp.nov.和采自浙江省科1新种:大磐山斑Pseudagrion daponshanensis,sp.nov.,模式标本保存于浙江自然博物馆昆虫标本室。     

The structure and function of the genitalia in the Libellulidae (Odonata)

An outline of the morphology of the secondary genitalia of libellulid dragonflies is given together with a more detailed treatment of the components of the fourth (distal) segment of the penis. The variations of penis structure in 70 species, representing ten of the 11 subfamilies, are surveyed and catalogued. There is remarkable diversity in the presence and form of penis structures, particularly those associated with the medial process, namely the flagelium, cornua and inner lobes. A comparable survey of females shows that they can be provisionally divided into ten types according to the number and size of their sperm-storage organs. Comparisons of penis structures with the sperm-storage organs of females suggests that in species whose females store large amounts of sperm, usually doing so in one or a pair of organs, males possess highly extensible, lobate and bristly penes, commonly equipped with cornua. By contrast, in those species in which the females store small volumes of sperm, usually doing so in three organs, the penes bear either flagella equipped with proximally directed spines or with large terminal barbs, or they have narrow, spiny inner-lobes which resemble flagella. Some functional interpretations are proposed in the light of sperm competition. The variability of genital structure can be interpreted adaptively and does not closely reflect phylogenetic relationships. Functionally convergent structures have evolved a number of times from different origins.     

Two gynandromorphs of Sympetrum striolatum (Charpentier, 1840) (Odonata: Libellulidae)

Two gynandromorphs of the dragonfly Sympetrum striolatum , with different features, are described here, with special emphasis on the genitalic structures.     

Emergence pattern,site selection,and seasonal regulation of Onychogomphus costae Selys, 1885 (Odonata: Gomphidae) in northeastern Algeria

Emergence and seasonal regulation of the dragonfly Onychogomphus costae Selys, 1885, were surveyed thoroughly during two consecutive years from two nearby stretches upstream the Seybouse River, northeastern Algeria. The emergence season started in mid-May and lasted 68 and 58 days showing a peak in late May and early June in 2011 and 2012, respectively. During the two years 2011 and 2012, 50% of annual emergence occurred after 25 and 22 days, respectively. Sex ratio was slightly but not significantly male biased. Female exuviae were recorded at higher height than males. Height of the exuviae fixation was positively correlated to support height and head width. Percentage mortality at emergence was mainly due to deformity and predation counting from 7.9% to 9.15% of the total emergent population. The species seasonal regulation is inferred and discussed based on the emergence temporal pattern and larval development.     

A checklist of the dragonflies (Odonata) of Kenya

A checklist of Odonata has been compiled for Kenya. It is based on an inventory of museum material, publications and personal observations made between 1978 and 1997. Changes of scientific names and synonyms are documented. The list contains 194 valid dragonfly species recorded for Kenya.     

Foraging behavior ofPachydiplax longipennis (Odonata: Libellulidae)

Food intake, prey availability, and prey capture behavior at feeding areas were quantified in the dragonflyPachydiplax longipennis by observing focal individuals on artificial perches, where they exhibited marked short-term site fidelity. Prey capture success was high and relatively constant, but the frequency and duration of feeding flights depended on the time of day and season (at least in part because of associated variation in temperature and other physical factors), study site, sex, density of other dragonflies, and prey density. Individuals rapidly responded temporally and spatially to changes in prey availability, particularly to localized prey concentrations.     

Polymorphic microsatellite loci to study population dynamics in a dragonfly,the libellulid Trithemis arteriosa (Burmeister, 1839)

One of the most widely distributed dragonfly species in Africa is the red‐veined‐dropwing Trithemis arteriosa. It is an indicator for permanent water bodies, which are freshwater ecosystems of high environmental value especially in arid regions. For studies to determine population structures, assess species viability and monitor environmental changes, a panel of 10 polymorphic microsatellite loci was developed. The number of alleles per locus ranged from four to 12, with an observed heterozygosity ranging from 0.149 to 0.843.     

Micro-morphological adaptations of the wing nodus to flight behaviour in four dragonfly species from the family Libellulidae (Odonata: Anisoptera)

Adult dragonflies can be divided into two major groups, perchers and fliers, exhibiting notably different flight behaviour. Previous studies have yielded conflicting results regarding the link between the wing macro-morphology and flight style in these two groups. In this study, we present the first systematic investigation of the micro-morphological differences of wings of percher and flier dragonflies in four closely related species from the family Libellulidae. Our results suggest that the shape and material composition of wing microstructural components and, in particular, the nodus are adapted to facilitate the specific wing functioning in fliers and perchers. The findings further indicate a decreasing trend in the area proportion of the soft resilin-dominated cuticle in the nodus in the series of species from typical perchers to typical fliers. Such a reduction in the resilin proportion in the nodus of fliers is associated with an increase in the wing aspect ratio. The knot-shaped protrusion at the nodus of perchers, which becomes notably smaller in that of strong fliers, is likely to act as a mechanical stopper, avoiding large wing displacements. This study aims to develop a novel framework for future research on the relationship between wing morphology and flight behaviour in dragonflies.     

Emergence pattern,microhabitat choice,and population structure of the Maghribian endemic Gomphus lucasii Selys, 1849 (Odonata: Gomphidae) in northeastern Algeria

Emergence of Gomphus lucasii Selys, 1849, an unstudied Maghreb endemic, was synchronised by overwintering in the final stadium in the Seybouse River in northeastern Algeria. Regular collections revealed that half of the annual population emerged during 10 days, showing a typical ‘spring species’ emergence pattern. Sex ratio was slightly male biased (51%). Males and females did not differ in vertical stratification. Emergence support choice was not random, but rather depended on support height, body size, and daily population density. Mortality was caused mainly by ants, although deformity of tenerals and bird predation were also important factors. Gomphus lucasii has been assessed as vulnerable (International Union for Conservation of Nature (IUCN) Red List), and the information provided in our study will be helpful in future conservation efforts.     

Large net cage for captive breeding and behavioural studies of damselfly Lestes sponsa (Hansemann, 1823) (Odonata: Lestidae): submerged oviposition as a model behaviour

Odonata have a strong potential as model organisms for testing ecological and evolutionary hypotheses because of their short life history, relative ease and cost-effectiveness of care. Unfortunately, very few studies have examined how to create a semi-natural environment for odonates, limiting the biological validity of laboratory manipulation. To better study odonate life cycle and behaviour under controlled conditions, we designed a large net cage that imitated the natural terrestrial as well as aquatic habitat of the damselfly Lestes sponsa (Hansemann, 1823). This species is thought to be capable of submerged oviposition, an unusual behaviour in odonates. We compared multiple variables across natural conditions and the net cage. We demonstrated that between-year variability under natural conditions was generally greater than variability between natural and artificial environments. Overall, semi-natural conditions did not substantially change the L. sponsa life cycle (including the unique behaviour of submerged oviposition), suggesting that results from the net cage are likely generalisable to the field.     

Function of abdomen wave behavior in larvalischnura verticalis (Odonata: Coenagrionidae)

Odonate larvae are important predators in the littoral zone of freshwater systems, and in an effort understand their population dynamics, researchers have described and analyzed many of their behaviors. The behavior we call abdomen wave has been considered to be both an aid to respiration and an aggressive display to conspecifics. We found that, under laboratory conditions, abdomen wave was not increased when the oxygen concentration was low or when larvae were in the presence of conspecifics. These results suggest the behavior is not involved in oxygen uptake or in agonistic interactions. The behavior was increased when larvae had food in their guts and was most dramatically increased in the hours preceding a molt. Abdomen wave may function to loosen the exoskeleton prior to molting and/or release of metabolites.