Reproductive properties of two sympatric dung beetles,Aphodius haroldianus andA. Elegans (Coleoptera: Scarabaeidae)

1. Reproductive properties of two sympatric dung beetles, Aphodius haroldianus and A. elegans, were studied at a pasture in the central Japan.
2. Overwintered adults of A. haroldianus came flying to dung pats from May to early August and bred from June to July. A. elegans overwintered as larvae, new adults came to dung pats from mid May to mid June. After aestivation, they reproduced from October to November.
3. A. haroldianus was a species with low fecundity and large food reserve for larvae. Female of this species had short duration of residence and laid fewer number of eggs in one dung pat. On the other hand, A. elegans was a species with high fecundity and small food reserve for larvae. Female of this species had long duration of residence and laid larger number of eggs in one dung pat.
4. The daily egg production in A. haroldianus reached a peak (0.40 eggs/female/day) at middle of oviposition period, but, that in A. elegans reached a peak (6.49 eggs/female/ day) at the beginning of oviposition period. The mortality of A. haroldianus female occurred after the daily egg production reached a peak and then rapidly increased, whereas that of A. elegans began soon after the beginning of oviposition and then gradually increased.

     

Studies on the population dynamics of a thistle-feeding lady beetle,Henosepilachna pustulosa (Kôno) in a cool temperate climax forest

Population Ecology -     

Effect of population density on reproduction of two sympatric dung beetle species,Aphodius haroldianus andA. Elegans (Coleoptera: Scarabaeidae)

The effect of population density on reproduction as well as the oviposition modes of two sympatric dung beetle species, Aphodius haroldianus (a low fecundity/high parental effort species) and A. elegans (a high fecundity/low parental effort species) was studied at a pasture in central Japan from 1982 to 1986.

1. The adult population density of A. haroldianus was high (>40 per dung pat). The density of A. elegans was low (<5 per dung pat). Oviposition of A. haroldianus was suppressed above the density of about 10 adults of conspecifics but not affected by the density of other species. The intra- and interspecific density effects on oviposition were not detected in A. elegans.
2. The number of A. haroldianus adults per pat decreased with dung age, while that of A. elegans increased until sixth day after deposition and then decreased. The number of eggs laid per pat was not different between 1-day-and 3-day-old pats for A. haroldianus. However, more eggs of A. elegans were found in 3-day-old pats than in 1-day-old ones.
3. In the both species, the amplitude of population fluctuations was not remarkable; the maximum/minimum ratio for five years being 2.3 for A. haroldianus and 2.9 for A. elegans. Different density dependent processes were suggested to function for the small fluctuation of population density between the two species, i.e. intraspecific density effect on oviposition for A. haroldianus and contest type competition for food among larvae of A. elegans.

     

Superposition optics and the time of flight in onitine dung beetles

Dung beetles fly to fresh dung, with vision essential for flight navigation. The daily period of flight varies among different species: some beetles fly only in sunlight, others only when ambient light levels change rapidly during dusk or dawn and others in the constant dark of night. Measurements of the optical properties of the lenses, eye geometry and photoreceptor dimensions were used in a computer ray-tracing model to determine the optical performance of the superposition eyes of nine species of onitine dung beetles. Eye sensitivity to light is determined mainly by body size, by the refractive-index parameters and size of the crystalline cones, and by the photoreceptor dimensions. Based on the optics of the ommatidial lenses and absorption of light in the retina, the most sensitive eyes, found in the crepuscular-nocturnal beetles, are 85 times or nearly two log units more sensitive than the eyes of the diurnal beetles. Three possible criteria are considered to determine the best position for the retina: maximum amount of light absorbed in the target rhabdom; maximum amount of light falling on the target rhabdom (best focus); and maximum resolution. The structure and physiological optics of the superposition compound eyes of an onitine dung beetle are matched to the range of light intensities at which it flies. Accepted: 4 February 1998     

Patterns of daily flight activity in onitine dung beetles (Scarabaeinae: Onitini)

Different species of African dung beetles emerge from the soil at characteristic times of the day to fly and colonize the freshly-deposited dung of mammalian herbivores. Onitine dung beetles in their natural habitat displayed one of five distinctive daily flight behaviours: dusk crepuscular (Onitis alexis Klug, O. caffer Boheman, O. fulgidus Klug, O. tortuosus Houston, O. vanderkelleni Lansberge, O. westermanni Lansberge); dusk/dawn crepuscular (O. pecuarius Lansberge and O. viridulus Boheman); dusk/dawn crepuscular and nocturnal (O. aygulus (Fabricius), O. mendax Gillet, O. uncinatus Klug); late afternoon-dusk and dawn-early morning [Heteronitis castelnaui (Harold)]; or diurnal flight activity [O. belial (Fabricius), O. ion (Olivier)]. These diagnostic daily flight behaviours span a light intensity range of over 6 orders of magnitude and have been retained in selected species introduced into Australia. Ambient light intensity appears to be the primary determinant of the daily flight period in onitine dung beetles. Because the dung of mobile herbivores is rapidly exploited by onitine species for feeding and breeding purposes, different flight behaviours result in a spatial and temporal partitioning of species in the local dung beetle community. The timing of flight may contribute to, or lead to avoidance of, competition between species which may ultimately affect colonization success. Many onitines show a strong preference for dung of specific herbivores, which may further reduce interspecific competition. All crepuscular-nocturnal species examined raised their thoracic temperatures endothermically to between 35°C and 40°C before the onset of flight. In O. aygulus the thoracic temperature excess was as large as 19.3°C. The thermal threshold below which the frequency of flight onsets drops off rapidly is about 12°C for O. aygulus and 17°C for O. alexis and O. pecuarius. Radiant loss of body heat during cool nights and dawns may explain why smaller species (<0.4 g body weight), in particular, are adapted behaviourally so that they fly only during the day or early dusk.     

Deforestation and biodiversity: effects of bushland cultivation on dung beetles in semi-arid Tanzania

Dung beetles provide important ecosystem services in the habitats where they occur. The activity of dung beetles enhances soil nutrient cycling and increases the soil’s ability to absorb and hold water. Consequently, these beetles are particularly important in semi-arid environments. This study analyses the importance of remaining wooded habitat patches (bushland) for the survival of a diverse dung beetle fauna in an otherwise cultivated landscape in semi-arid Tanzania. Dung beetles were sampled by pitfall trapping in maize fields and bushland habitats. In total, 6037 dung beetles (Scarabaeidae: Scarabaeinae), representing 77 species from 25 genera, were collected. Many species, particularly amongst the ball-rollers, showed a clear preference for wooded patches, species richness being significantly higher in the bushland patches than in the cultivated sites. The number of trapped specimens in bushland was also considerably higher than that found in maize fields, although the differences were not significant. In conclusion, bushland fragments appear to have an important conservation value as to maintaining a high diversity and abundance of dung beetles, thereby enhancing the ecosystem services provided by these beneficial insects.     

An old adaptive radiation of forest dung beetles in Madagascar

Adaptive radiations of mammals have contributed to the exceptionally high levels of biodiversity and endemism in Madagascar. Here we examine the evolutionary history of the endemic dung beetle tribe Helictopleurini (Scarabaeidae) and its relationship to the widely distributed Oniticellini and Onthophagini. Helictopleurini species are dependent on mammals for their resources. We date the single origin of the tribe at 37 to 23 MY ago, indicating overseas colonization of Madagascar. The main radiation occurred concurrently with the main radiations of lemurs. The ancestors of Helictopleurini are inferred to have been coprophagous species inhabiting open habitats. Subsequent evolution has involved a shift into forests, changes in resource use to a more generalized diet, and changes in body size. Four species of the extant 65 species have shifted to use the dung of the recently introduced cattle in open habitats, allowing these species to greatly expand their geographical ranges.     

Getting the most out of waste: how dung beetles boost the nitrogen content in their food

The life cycle of almost all dung beetles revolve around mammalian dung, the feed on dung, look for mating partners on dung and lay eggs in the dung. We know they feed on dung, but we still do not understand how exactly they filter‐feed on the dung and which particles size range they are ingesting. The aim on this study was to investigate the filter feeding by particle selection by adult dung beetles using Scarabaeus goryi and how that improves the nutrient quality of the ingested particles. We compared the particle sizes and nutrient content of the dung with the ingested material in the foregut, hindgut and the faeces of the dung beetle. Adult dung beetles do select smaller dung particles when feeding, we found the maximum particle size for the ingested particle to be around 1400 μm. The average particle size increased through the gut length. Dung beetles also selected particles with higher nitrogen content when feeding, the nitrogen content increased from about 1.5% in the dung to just over 5% in the foregut which then decreased to the level of the unprocessed dung in the dung beetle faeces. Carbon content did not increase from the unprocessed dung to the foregut but decreased through the gut length. Feeding by particle size selection by dung beetles helps in selecting particles with higher nitrogen content to compensate for the low levels found in dung.     

Movement patterns of Cetonia beetles (Scarabaeidae) among flowering Viburnum opulus (Caprifoliaceae)

The movement patterns of flower-visiting Cetonia (Coleoptera, Scarabaeidae) were studied in central Sweden over 4 years, providing the first quantitative study of beetle pollination behaviour conducted in a temperate zone. The beetles were marked individually and tracked throughout their visits to Viburnum opulus L. (Caprifoliaceae), a partly beetle-pollinated shrub displaying large umbel-like, creamy-white blossoms. Beetle abundance differed greatly between study years. Of marked beetles observed on V. opulus flowers, an average of 26% returned each year. The beetles performed frequent inter-plant flights, and showed fidelity to particular V. opulus individuals at the study site. Furthermore, they preferred V. opulus to other plants flowering concomitantly and showed considerable constancy in this habit. Movements were mostly between individuals from unshaded locations with high inflorescence and flower number. Normally, the beetles flew on average about 4 times the horizontal nearest-neighbour distance between flowering V. opulus (c. 18 m). From these observations it is concluded that Cetonia beetles are powerful long-distance dispersal agents for V. opulus pollen, perhaps leading to an enhanced gene flow not possible with the plant's other pollinators.     

Diversity of dung and carrion beetles in a disturbed Mexican tropical montane cloud forest and on shade coffee plantations

This paper analyzes the diversity of dung and carrion beetles (Scarabaeinae and Silphidae) in four human-induced habitats of a disturbed tropical montane cloud forest: polyspecific shade coffee plantations, monospecific shade coffee plantations, tropical montane cloud forest fragments, and clear cuts. The four habitats had similar richness, species composition, and assemblage structure of dung and carrion beetles. Differences were found in abundance and biomass levels for the four dominant species in the landscape. Dung beetles were more abundant than carrion beetles, but the biomass was higher for the latter. Carrion beetles were seasonal, while dung beetles were clearly not. When forest fragments and shade coffee plantations were compared to other similar habitats in the region, the same general pattern was observed. However, forests with high disturbance and monospecific shade coffee plantations had lower species richness than forests with low and medium disturbance and polyspecific shade coffee plantations. Thus shade coffee plantations maintain connectivity between patches of cloud forest in a landscape that is strongly affected by human activities. Protecting landscape diversity appears to ensure high species richness.     

Sexual selection and condition dependence of courtship display in three species of horned dung beetles

Sexual selection has traditionally been divided into competitionover mates and mate choice. Currently, models of sexual selectionpredict that sexual traits are expressed in proportion to thecondition of their bearer. In horned beetles, male contestcompetition is well established, but studies on female preferencesare scarce. Here I present data on male mating success and condition dependence of courtship rate in three species of horn-dimorphicdung beetles, Onthophagus taurus, Onthophagus binodis, andOnthophagus australis. I found that in the absence of malecontest competition, mating success of O. taurus and O. australiswas unrelated to their horn length and body size, whereas inO. binodis horn size had a negative effect but body size hada positive effect on male mating success. Overall, in O. binodismajor morph males had greater mating success than minor morphmales. In all three species male mating success was affectedby courtship rate, and the courtship rate was condition dependent such that when males were manipulated to be in poor conditionthey had lower courtship rates than males that were manipulatedto be in good condition. My findings provide new insight intothe mating systems of horned dung beetles and support an importantassumption in indicator models of sexual selection.     

Adjustment of parental expenditure in sympatric <Emphasis Type="Italic">Onthophagus</Emphasis> beetles (Coleoptera: Scarabaeidae)

Many organisms adjust their parental expenditure to offspring in response to resource quality. However, the mechanisms underlying the adjustment in parental expenditure are not well understood. We examined the adjustments in parental expenditure and subsequent offspring performance in two sympatric, closely related dung beetles, Onthophagus ater and O. fodiens, that were provided either monkey, deer, horse, or cow dung. The egg contained within each dung brood mass provisioned by the parent beetles develops to adulthood underground. Thus, the size of the brood mass roughly represents the amount of parental expenditure. The brood mass size differed between the two species and among the four dung types. Results of offspring performance suggested that O. ater parents optimally adjusted the brood mass size in response to dung quality, whereas O. fodiens parents did not. We hypothesized that brood mass size in O. ater may increase with prolonged egg maturation caused by the lower nutrition level of cow dung. In addition, our complex results may be explained in part by the specific threshold concept of dung quality (i.e., water content and nutritional level).     

The process of population increase and patterns of resource utilization of two spider mites,Oligonychus ununguis (Jacobi) andPanonychus citri (McGregor), under experimental conditions (Acari: Tetranychidae)

Summary Pattern of population growth and characteristics of habitat utilization and of migration by two species of spider mites were studied under experimental conditions. The population growth ofOligonychus ununguis (Jacobi) on a chestnut occurred only on a single mite-release leaf over a long period, and few individuals moved away. Most of the 2nd progeny generation females of this species emigrated from the mite-release leaf as well as the sapling by means of ballooning threads. During this growth period, population density on the mite-release leaf levelled off, whereas that on the sapling increased. In contrast, the foundress ofPanonychus citri (McGregor) on citrus actively moved over several neighbouring leaves, and until the 2nd progeny generation females emerged, individuals were distributed over all the sapling leaves by means of walking. Emigration from the sapling was not observed until the 2nd progeny females emerged, and after that the mites emigrated by means of ballooning threads. The population density ofP. citri on the sapling levelled off and was rather decreased on the mite-release leaf at the time of mite emigration. Comparing the changing pattern of the relative degree of aggregation (m ^*/m) measured in two different units between these two species, the pattern ofm ^*/m in 1 cm² on the mite release leaf inO. ununguis resembled that of the unit of leaves on the sapling inP. citri. This result as well as behavioural observations indicate that migration ofO. ununguis is the movement from leaf to leaf and that ofP. citri from sapling to sapling. It is, therefore, concluded that the boundary of the microhabitat is a single leaf forO. ununguis but sapling or foliage forP. citri. This work was presented in Annual Meeting of Jap. Soc. Appl. Ent. Zool., 1981 in Okayama.     

Geographical variation of elytral spot patterns in the phytophagous ladybird,Epilachna vigintioctopunctata (Coleoptera: Coccinellidae) in the Province of Sumatera Barat,Indonesia

Geographical variation in the elytral spot patterns of a phytophagous ladybird, Epilachna vigintioctopunctata, was studied in the Province of Sumatera Barat, Indonesia. Populations of E. vigintioctopunctata were divided into four major groups (I–IV) by the incidence of spot pattern variations. Group I, occurring in the coastal plains and inland lowlands, and Group IV, confined to the highlands, were the extremes of the spot pattern variations, the latter had many more non-persistent spots and confluences with larger body size and advanced melanism than the former. These two groups were connected with each other via the intermediate groups. A positive relationship was detected between the elevations of sample sites and the average number of non-persistent spots per elytron. Consequently, present results favor the view that the two previously recognized forms of E. vigintioctopunctata (formae A and B inKatakura et al., 1988) represent a complicated intraspecific variation rather than two distinct sibling species. Elytral spot pattern variations were not different between the sexes or between the beetles collected from different kinds of host plants.     

Dynamics and distribution patterns of acarine populations in stored-oat ecosystems

Population dynamics and aggregation patterns of nine kinds of stored-grain mites were studied in two 7.5 tonne lots of hulled (cv. Random) and hulless (cv. Terra) oat cultivars with 12–14% moisture content stored in two wooden bins in Manitoba, Canada during 1978–84. Random oats harbored more mites than Terra oats. Lepidoglyphus destructor Schrank was the most common granivorous mite and Cheyletus eruditus Shrank the most common predatory mite. Ecological data on a tydeid mite, Paratriophtydeus coineaui André, are presented for the first time. Because they were more abundant in Terra oats with higher fat acidity values (FAV) than Random oats with lower FAVs, L. destructor and Tarsonemus granarius Lindquist could be used as bioindicators of spoilage of stored oats. All species analyzed showed some significant difference in their abundance at different depths in the grain bulk; some species showed depthxtime interaction. Aggregation patterns indicated most mite species had overdispersed (clumped) distribution. T. granarius, and Blattisocius keegani Fox-Androlaelaps casalis Berlese had a distinct aggregation pattern in each oat cultivar.     

Neuronal adaptation improves the recognition of temporal patterns in a grasshopper

The recognition of the temporal structure of sound patterns by grasshopper males was investigated in behavioural experiments. Males were tested with short (165–335 ms) song models in which the characteristic subunit pattern of syllables and pauses was modified either at the beginning or at the end of the stimuli. The highly specific responses of the animals indicate that neuronal adaptation has a substantial influence on the detection of the pauses which are essential cues for the subunit structure: pauses were less likely detected shortly after the beginning of a song model than at later positions. Even adaptation in auditory neurons that was induced by unspecific stimulation (with unmodulated noise) facilitated the processing of sound envelopes. The effects of stimulus prolongation and introduction of pauses appeared to combine linearly, similar to the effects of introducing two pauses instead of a single one. In the responses to some song models large interindividual differences were observed. Comparison across stimuli and repeated testing of a smaller number of individuals indicated a considerable consistency of behavioural preferences. However, the data yielded no clear evidence for the existence of individually distinct processing types among males, that conceivably would focus on different features of the stimuli.     

Major species of the dung beetles (Superfamily: Scarabaeoidea) in three ecological systems in western Saudi Arabia

Members of the dung beetles superfamily Scarabaeiodea (families: Scarabaeidae and Aphodiidae) represent a major part of the ground‐dwelling fauna in a natural (fallow) and two agroecosystems in Western Saudi Arabia. The most abundant species include Pentodon algerinum Herbst and Aphodius assectora Balth. during the main activity period October‐May. Statistical analysis showed that there were no significant differences in the population density of both species between the three ecosystems under investigation. A pronounced peak of P. algerinum observed during November in the vegetable agroecosystem whereas a sharp peak observed during March in the natural (fallow) ecosystem. A. assectora was the dominant species with a sharp peak during February‐April in the vegetable agroecosystem which might be attributed to the abundance of decaying organic matter that resulted from crop harvesting. P. algerinum is active during early and late seasons October‐December and February‐April in the vegetable agroecosystem and natural (fallow) ecosystem respectively, whereas A. assectora is active during late season, February‐April in the vegetable agroecosystem. Low population numbers of both species were recorded in the datepalm agroecosystem which might be attributed to the predatory pressure exerted by residents of both Avian and vertebrate predators having continued presence and feeding on a high protein diet of immature and adult stages of both beetles.     

Phylogeographical patterns and genetic diversity in three species of Eurasian boreal forest beetles

Many species that occur in formerly glaciated areas of Fennoscandia have reached their current ranges from glacial refugial areas in Eurasia. Little is known of the refugia and postglacial colonization routes of insect species that are confined to boreal forests. Here, we investigate the phylogeography of three species of saproxylic beetles distributed across Eurasia: two rare boreal forest specialists, Pytho kolwensis and Pytho abieticola , and a common, less specialized species, Pytho depressus . In all species, there were two well-defined haplotype clades based on 645 bp of cytochrome oxidase subunit I gene sequence. In each species one clade was found only in China. The other clade occurred from China to north-western Europe in both P. kolwensis and P. depressus , but was apparently absent from China in P. abieticola. In spite of common phylogeographical patterns, the distribution of genetic variation differed markedly between the three species. In P. kolwensis , a highly-threatened species in old-growth forests in Fennoscandia, there was an extremely low level of genetic variation throughout Eurasia. One common haplotype, represented by 86% of the samples, dominated in all sampling localities. Levels of genetic variation were higher in both P. abieticola and P. depressus , with 31% and 58%, respectively, of the samples representing a unique haplotype. In each species, relationships between haplotypes were not well resolved, and haplotypes from one sampling locality were generally not clustered in either Neighbour-joining trees or statistical parsimony networks. These patterns in the distribution of genetic variation can be attributed to differences in the species' population sizes, ecologies, glacial refugial areas, and postglacial colonization dynamics.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 267–279.