Effects of dung beetles on seedling emergence from herbaceous seeds in the dung of sika deer (<Emphasis Type="Italic">Cervus nippon</Emphasis>) in a temperate Japanese grassland ecosystem

The effects of dung form and condition and of dung beetles on the emergence of seedlings from herbaceous seeds in sika deer dung were examined in a temperate grassland ecosystem dominated by Zoysia japonica and Hydrocotyle maritima. I conducted field experiments to compare seedling emergence between dung exposed to dung beetles and intact dung using both dung pellets and pats during a typical rainy month (June) and the hottest, drier month (August), when large numbers of seeds of the dominant species were present in the dung. The exposed dung was immediately attacked and broken up by dung beetles, whereas dung protected from the beetles remained intact. In June, at least 12 herbaceous species, including Z. japonica, H. maritima, Mazus pumilus, and Plantago asiatica, emerged from the dung, versus at least six species in August. Decomposition rates of the pellets in June and decomposition scores of the pats in June and August were positively correlated with the number of emerging seedlings, suggesting that the acceleration of decomposition by dung beetles can positively affect seed germination. In this system of interactions among sika deer, herbaceous plants, and dung beetles, sika deer dung prevented seeds from germinating, and beetles had an indirect positive effect on seedling emergence by accelerating decomposition of the dung, although the extent of the effect may depend on the dung type, plant species, and environmental factors.     

Crepuscular activity of adult Sericesthis geminata (Coleoptera: Scarabaeidae): Influence of circadian rhythmicity and light intensity

Subterranean Sericesthis geminata (Boisduval) beetles emerge from the soil daily during the flight season. Emergence and flight are initiated within 15 min after sunset. The beetles are active above the soil surface as the intensity of illumination decreases from 240 lux to 0.7 lux.

If young adult beetles still in their pupal cells in the soil are placed under constant, low‐intensity illumination, they first emerge at any time of day, showing no cyclical diurnal activity pattern. When such beetles are exposed to diurnal fluctuations in illuminance, the first emergence and flight occur at dusk. These beetles subsequently show a diurnal rhythm in their activity, even when exposed to constant environmental conditions. This endogenous activity cycle has a period of about 22 h, and is synchronised with diurnal fluctuations in light intensity. It is reset in response to a change in the photoperiod.

The data suggest that, after initial emergence from the soil, daily crepuscular activity is initiated by an endogenously controlled activity rhythm which causes the beetles to burrow to the soil surface shortly before dusk. At the soil surface they are exposed to fluctuations in the duration and intensity of illumination which may reset the endogenous rhythm, affecting the time of subsequent emergence.     

Ground-dwelling predators can affect within-field pest insect emergence in winter oilseed rape fields

We investigated, (i) whether the emergence from pupation of two coleopteran pest insect groups in oilseed rape (OSR, Brassica napus L.)—pollen beetles (Meligethes spp. F., Nitidulidae) and stem weevils (Ceutorhynchus pallidactylus Marsh and C. napi Gyll., Curculionidae)—is affected by the exclusion of ground-dwelling predatory arthropods, and (ii) the role for pest control of the widely abundant carabid beetles Anchomenus dorsalis Pontop. and Poecilus cupreus L. Densities of ground-dwelling arthropods were manipulated using enclosures; emerging pest adults were assessed using emergence traps. Where arthropods had been excluded, between two (June sampling) and tenfold (August sampling) more stem weevils emerged than where predators had free access. The addition of 25 adult A. dorsalis m⁻² to formerly predator-free enclosures showed similar stem weevil emergence than plots where predators had free access; the addition of 25 adult P. cupreus m⁻² did not reduce stem weevil emergence. In August, both A. dorsalis and P. cupreus additions marginally significantly reduced pollen beetle emergence. Handling editor: Patrick De Clercq.     

Dormancy and the influence of photoperiod and temperature on sexual maturity in Nicrophorus nepalensis (Coleoptera: Silphidae)

Abstract Carrion beetles (Nicrophorus spp.) use small vertebrate carcasses for food and reproduction. Their ecology and behaviors are highly affected by the availability of carcasses and the surrounding environmental conditions. Our results revealed that in subtropical Fushan, northern Taiwan, N. nepalensis was mainly active in spring (February to May), and could also be found in autumn (October and November); but there was no capture record in summer (June to September) and winter (December and January). A laboratory temperature tolerance study indicated that N. nepalensis adults become inactive at temperatures above 26°C, and had the highest mortality when the temperature was raised from 27°C to 28°C. Furthermore, N. nepalensis became sexually mature at 20°C, depending on the photoperiod: the longer the day, the lower the percentage of sexually mature 2‐week‐old females after emergence. In another experiment, N. nepalensis virgins were paired under three possible conditions at Fushan. At 15°C and 20°C, if carcasses were presented to the pairs within 3 days after emergence, all laid eggs in the second week after emergence. If carcasses were presented 1 week after emergence, most began to reproduce at 20°C with 12.5 h of daylight. However, at 15°C with 11 h of daylight, the carrion beetles hibernated first, and reproduced in the ninth week after emergence. At 25°C with 14 h of daylight, carrion beetles did not bury the mouse carcasses, the females did not lay eggs, and the adult lifespan was only one‐third of that at 20°C. This study revealed that both photoperiod and temperature influence the time needed to reach the sexual maturity of N. nepalensis; and also implied that the narrow temperature tolerance range and dormancy behavior of carrion beetles are highly regulated by those environmental factors.     

Effects of age, sex, and dietary history on response to cucurbitacin in Acalymma vittatum

The chrysomelid Acalymma vittatum is stenophagous, subsisting almost entirely on plants in the Cucurbitaceae, which generally contain cucurbitacins. Cucurbitacins are extremely bitter tetracyclic triterpenoids that are toxic to most organisms. As do other diabroticite beetles, A. vittatum sequester cucurbitacins, which have been shown to act as phagostimulants and arrestants. Our results reveal, however, that for A. vittatum the response to cucurbitacin diminishes with continued sequestration. Colony-reared A. vittatum were fed only roots (as larvae) and foliage of either `Marketmore 76' (which contains a normal amount of cucurbitacin, `bitter') or `Marketmore 80' (a near isogenic line that contains no cucurbitacin, `non-bitter') cucumber. Over 1200 individual beetles from the day of adult emergence to 15 days following emergence were placed in choice and no-choice arenas containing potted cotyledons of the two cucumber varieties for 24 h. In choice tests, overall preference for the bitter cucumber cultivar was maintained, but degree of preference changed with age and became significantly less for beetles reared on bitter diets. Furthermore, in no-choice tests, age, sex, dietary history, and interactions among these variables all significantly affected the feeding response to cucurbitacin. For A. vittatum reared without cucurbitacin, total consumption of the bitter cultivar increased over time. For beetles reared with cucurbitacin, total foliage consumption of the bitter cultivar declined, within nine days, to equal that of the non-bitter cultivar. Feral A. vittatum, unexpectedly, consumed more of the non-bitter than the bitter cultivar in no-choice tests. Ecological and applied implications of this variation in response to cucurbitacin are discussed.     

Aggregation in a Desert Tenebrionid Beetle: A Cost/Benefit Analysis

Parastizopus armaticeps (Coleoptera: Tenebrionidae), a nocturnal fossorial detritivore inhabiting southern Kalahari dunes, aggregates in burrows during the day. Group size increases during drought but 25% of beetles are still found alone or in pairs. During drought, beetles from large groups leave burrows after sunset synchronously and carlier than pairs and single animals and earlier than beetles of any group size after rain. Detritus from the beetles' major foodplant is scarce and food competition high. Beetles emerging early preferentially select and carry high-quality transportable items into burrows to eat (forage); late-emerging ones feed on the low-quality large twigs on the surface. Foraging is shown to be a strategy to secure food items against surface competitors, not one to reduce body water loss during surface exposure. The costs and benefits of group vs. solitary lifestyles and alternate hypotheses for early and synchronous emergence were tested experimentally. Grouped beetles had lower body water loss rates but, due to competition with burrow mates, higher feeding costs than single ones. It is hunger that advances and thus synchronizes emergence time, not social facilitation. Field data support a model predicting that, for maximal benefits, beetles should alternate between solitary and group life at optimal time intervals.     

Post emergence maturation of the eye of the adult black carpet beetle,Attagenus megatoma (Fab.): An electron microscope study

The black carpet beetle, Attagenus megatoma (Fab.), has been reported to exhibit negative phototaxis immediately after emergence. In later adult life, after the period during which most oviposition has occurred, the beetles are found to be photopositive. The compound eyes of one-day-old (Post-emergence) and nine-day-old (Post-ovipositional) female beetles were studied by electron microscopy and a number of strong differences were found between eyes at the two ages. The corneal facets of one-day eyes had the form of convex-concave lenses, while those of nine-day beetles were double-convex lenses. The primary and secondary pigment cells of young eyes were large and contained much endoplasmic reticulum and little accessory pigment. In the older eyes the pigment cells were reduced and contained much pigment, the proportion of endoplasmic reticulum being greatly reduced by comparison with the one-day eye. The cross-sectional area of the rhabdom was greater in the older eye. The possible relationships between age-related changes in eye morphology and behavioral changes during the same period are discussed.     

Factors influencing adult emergence from soil and the vertical distribution of burrowing scarab beetles Dasylepida ishigakiensis

The present study investigates the emergence of adult white grub beetles Dasylepida ishigakiensis Niijima et Kinoshita (Coleoptera: Scrabaeidae) from soil as well as their burrowing behaviours. ‘Standby behaviour’ (i.e. adults come to the soil surface where they expose their heads) is shown in the field and, along with emergence behaviour, is entrained by LD photocycles. These 24‐h rhythms persist after transfer to continuous light conditions for 2 days. By contrast, beetles transferred from LD photocycles to continuous dark conditions fail to show standby behaviour; thus, it appears to be manifested only in the presence of illumination. Under dark conditions, beetles emerge completely from the soil directly at the time when standby behaviour is otherwise expected to occur. Emerged adults then burrow back into the soil before dawn. Virgin and mated males, as well as virgin females, which are expected to emerge from the soil for mating on later evenings, burrow to a relatively shallow depth (<2 cm), whereas mated females burrow deeper (2–10 cm). Soil properties such as moisture, grain size, topography and temperature influence the burrowing behaviour and the depths that the beetles reach.     

Seasonal flight patterns of Ips typographus in southern Sweden and thermal sums required for emergence

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Survival, longevity and fecundity of overwintering Mesoplatys ochroptera Stål (Coleoptera: Chrysomelidae) defoliating Sesbania sesban (Leguminosae) and implications for its management in southern Africa

1 The defoliator beetle, Mesoplatys ochroptera Stål, is a serious pest of the legume tree sesbania (Sesbania sesban (L.) Merrill) in agroforestry systems in southern Africa. The survival of the overwintering stage of M. ochroptera and post‐ emergence longevity and fecundity of adults in sesbania fallows in eastern Zambia were quantified. 2 Only adult M. ochroptera survived during the winter (May–August) and the dry season (September–October) hidden under weeds, plant litter, in soil cracks and under rocks. During these periods, some beetles were occasionally found feeding on S. sesban, particularly in natural stands in humid areas. The adults were parasitized by the braconid Perilitus larvicida van Achterberg at a rate of 8.5–16.4%. The beetles stayed in the winter refuges for up to 210 days and emerged with the first heavy rains in October–November. The effective survival of beetles overwintering in an insectary was 18.1% in 1998 and 37.7% in 1999, and that of beetles overwintering in the field was estimated at 0.4 and 2.8% in 1998 and 1999, respectively. 3 The post‐emergence longevity and oviposition period of females in the insectary was 14–31 days and 5–29 days, respectively. The post‐emergence fecundity varied from 87 to 783. 4 It is concluded that the serious M. ochroptera infestation observed every year following the rains is due to synchronous emergence of overwintered resident adult populations and their high capacity for reproduction on many species of Sesbania. Recommendations for pest management in sesbania planted‐fallows are given.     

An alternative hibernation strategy involving sun-exposed 'hotspots', dispersal by flight, and host plant finding by olfaction in an alpine leaf beetle

Oreina cacaliae (Schrank) (Coleoptera: Chrysomelidae) has a 2‐year life cycle that it has to complete within the short warm seasons of the harsh alpine environment. Three years of field observations and experiments revealed that not all beetles overwintered in the soil next to their principal host Adenostyles alliariae (Asteraceae), as was previously assumed, but that many O. cacaliae left their host in autumn and flew to overwintering sites that were extensively sun‐exposed. In spring, these individuals became active 2 months earlier than their conspecifics that had remained in the soil close to the host plant. These early beetles flew from their hibernation sites against the direction of the prevailing wind. After a random landing in snow, they walked to the spring host Petasites paradoxus (Asteraceae) and fed on its floral stalks, the only plant parts present at that time. A few weeks later, they took flight again to locate newly emerging A. alliariae on which they would feed and deposit larvae as did individuals that had overwintered close to A. alliariae. Leaves of A. alliariae contain pyrrolizidine alkaloids (PAs), which the beetles sequester for their own defence. The dominating PA (seneciphylline) was also found to be present in the floral stalks of P. paradoxus. With additional behavioural assays in the field and laboratory, we demonstrated the importance of plant odours in the short‐range host location process. This study reveals a unique hibernation behaviour in which part of the beetle population uses exceptionally warm locations from which they emerge in spring, long before all the snow has melted. This early, but risky emergence allows them to exploit a second, highly suitable host plant, which they locate first by wind‐guided flight and then by odour‐guided walking. The well‐fed beetles then use odour again to move to their principal host plant, on which they reproduce.     

Dispersal and influences on movement for Anoplophora glabripennis calculated from individual mark-recapture

We conducted an individual mark‐release‐recapture experiment on the beetle, Anoplophora glabripennis Motchulsky (Coleoptera: Cerambycidae). This invasive beetle has been introduced from Asia to Europe and North America and poses a serious threat to several important species of tree. Eradication efforts may benefit from knowledge of dispersal behaviour. Trees were cut and held to determine emergence rate of A. glabripennis. Unique marks were painted onto 912 beetles released into a group of 165 trees in Gansu, China. Data on subsequent sightings of beetles were used in a truncated diffusion model to calculate flight distances. Characteristics of the trees and climatic information were used in statistical tests for influence on movement. A total of 2245 sightings of beetles were observed and 29% of marked beetles were resighted. The scanning technique using binoculars was 90% effective in finding beetles and provided 81% accuracy for determining the sex of the beetles. Experimental manipulation of density quantified how A. glabripennis congregated on unoccupied trees and were repulsed from crowded hosts. The seasonal emergence rate of adults declined exponentially from July 20 to August 5. The results suggested A. glabripennis fly to nearby host trees at a rate of 34% per day. Median flight distance was estimated at 20 m per day. Statistical analysis with a generalized linear model tested the beetle's propensity to leave a tree and distance of flight. Generally, beetle movement showed a significant response to beetle density, weather conditions, beetle size, and tree size, in that order. The techniques developed here improve on previous recapture techniques to quantify dispersal and can be useful for analysing populations of other organisms.     

Quantifying rates of random mating in western corn rootworm emerging from Cry3Bb1‐expressing and refuge maize in field cages

The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is the most significant pest of field maize, Zea mays L. (Poaceae), in the USA. Maize plants expressing Bt toxins targeting the corn rootworm complex have been widely adopted and are the primary insecticidal control measure for this pest in North America. Insect resistance management tactics using various refuge structures have been adopted to ensure Bt products will retain durability. An assumption of the refuge strategy is that males and females emerging from Bt and refuge plantings mate randomly; this has not been tested in the field. We conducted cage studies using field populations of WCR in Indiana, USA, to generate empirical field data on mating rates between beetles emerging from Cry3Bb1‐expressing Bt and refuge maize plants. Two refuge configurations were tested; all refuge plants were labeled using the stable isotope ¹⁵N. This mark persists in adult beetles after eclosion, allowing for collection and analysis of isotopic ratios of all beetles. Additional data collected included adult emergence rates, timing and sex ratios for each of the treatments, and head capsule size and dry weights of beetles collected. Treatment had a significant effect on dry weight; mean dry weight decreased in Bt‐only treatments. Fisher's exact test of proportions of mating pairs of refuge and Bt insects indicated that mating was not random in 20% strip refuges and 5% seed blend treatments. We found high percentages of beetles that fed on Bt‐expressing plants as larvae, suggesting that mating between resistant beetles may not be rare even if random mating did occur.     

A two‐step mechanism controls the timing of behaviour leading to emergence from soil in adult males of the scarab beetle Dasylepida ishigakiensis

Adults of the white grub beetle Dasylepida ishigakiensis Niijima et Kinoshita (Coleoptera: Scarabaeidae) emerge from the soil around dusk for mating on subtropical islands. The present study examines the factors controlling the emergence of males in the laboratory. There are two steps involved. Standby behaviour (i.e. insect head appears at the soil surface) can be observed for several hours before the beetles actually emerge for mating. The standby behaviour is facilitated by warm conditions, although the proportion of standby individuals is influenced not only by the temperature on that day, but also by that on the previous day. Experiments in which beetles are exposed to photoperiod and thermoperiod combinations, in and out of phase, show that temperature is more important in inducing standby and emerging behaviour than light alone. For the second step, factors such as temperature, light and the presence of the female sex pheromone determine whether males will leave the standby position and emerge onto the ground. The female sex pheromone stimulates standby beetles to exhibit emerging and wing vibration behaviours, although the effect depends on when it is presented to beetles. Beetles burrow back into the soil; this behaviour is influenced by illumination and time of the day but not by temperature. The results suggest that D. ishigakiensis possesses a sophisticated mechanism controlling male emergence from the soil.     

Emergence patterns of univoltine and bivoltine Ips typographus (L.) populations and associated natural enemies

Control measures aiming at reducing bark beetle populations and preserving their natural enemies require a sound knowledge on their overwintering and emergence behaviour. These behavioural traits were investigated in univoltine and bivoltine populations of the European spruce bark beetle (Ips typographus [L.], Coleoptera: Scolytinae) and its predators and parasitoids over several consecutive years. In univoltine populations, roughly 50% of the bark beetles left their brood trees in fall together with most parasitoids and some significant predatory flies and beetles. In bivoltine populations, <10% of the second bark beetle generation emerged in fall and the remainder overwintered under the bark of their brood trees. Likewise, most predatory beetles and flies spent wintertime with their prey under the bark, while most parasitic wasps emerged in fall. The spring emergence of bivoltine predatory beetles was found to occur up to 3 weeks earlier than that of I. typographus, while that of the predatory flies and the parasitoids was delayed by up to 1 month. In univoltine populations, the bark beetles emerged several weeks prior to most antagonistic taxa. In the heat year 2003, three I. typographus generations were produced at the lower location, 36% of the third generation emerged in fall, while the proportions of overwintering predators remained largely the same as in previous years. Similar to their host, more parasitoids left their brood trees in fall after warm years. The results show that sanitation felling during winter probably kills most bark beetles in bivoltine populations, but also eliminates many natural enemies. In univoltine populations, sanitation felling might be less detrimental to both I. typographus and natural enemies because a fair fraction of their populations will already have left the trees before cutting. Warmer climates may affect the interactions of bark beetles and natural enemies and thus the impact of control measures.     

Overwintering biology ofMyiopharus aberrans andMyiopharus doryphorae (Dipt.: Tachinidae) larval parasitoids of the colorado potato beetle (Col.: Chrysomelidae)

The overwintering biology ofMyiopharus aberrans (Townsend) andMyiopharus doryphorae (Riley), tachinid parasitoids of the Colorado potato beetle, was investigated. Sixty seven overwintered Colorado potato beetle adults were dug from the soil before beetle emergence in the spring of 1990 from a field that had been planted to potatoes the previous year. Five adultM. aberrans and two adultM. doryphorae flies were reared from seven beetles. This is the first record of howM. aberrans andM. doryphorae flies overwinter.      

A sex-specific tri-trophic-level effect in a phoretic association

Hemisarcoptes coccophagus (Acari: Astigmata: Hemisarcoptidae) is an obligate parasite of armored-scale insects (Homoptera: Diaspididae). Hypopodes (non-feeding heteromorphic deutonymphs) of this mite cannot complete their development without a phoretic sojourn on the coccinellid beetle Chilocorus bipustulatus. We tested whether the feeding history of the beetles affects the probability of the hypopodes completing their development. Two diets were offered: armored-scale insects (Homoptera: Diaspididae) (suitable for both beetles and mites) and soft-scale insects (Homoptera: Coccidae) (suitable for the beetles but not for the mites). The hypopodial survival was similar for mites which had been on beetles reared on the different scales. However, female hypopodes which had stayed on beetles reared on soft scales suffered higher mortality than those from Chilocorus reared on armored scales. Male survival was not affected. A tri-trophic-level effect on sex-specific survival in a phoretic association was thus demonstrated.     

Transmission of the pine wood nematode Bursaphelenchus xylophilus through feeding activity of Monochamus galloprovincialis (Col., Cerambycidae)

Abstract:  Transmission of the pinewood nematode (PWN) Bursaphelenchus xylophilus (Steiner & Bührer) Nickle to Pinus pinaster Aiton branches through feeding wounds of its vector in Portugal, Monochamus galloprovincialis Olivier, was studied under laboratory conditions. All the B. xylophilus -infected beetles transmitted nematodes to branches they fed. The transmission was more frequent during the first 6 weeks after emergence, with transmission peaks during the second and the sixth week. The adult M. galloprovincialis transmitted nematodes for a mean of 5 weeks, independently of the beetle's sex or longevity. No relation was found between beetle feeding intensity and effective transmission of B. xylophilus to the branches. The nematode transmission ceased after the ninth week, even in insects which still had B. xylophilus on their bodies. The longevity of the nematode-free insects (control group) was slightly higher than the B. xylophilus -infected beetles, although with no significant difference. The results emphasize the necessity to control the immature stages of M. galloprovincialis prior to emergence and develop efficient strategies to capture and eliminate the recently emerged beetles, as majority of the nematode infection of healthy pine trees occurs during a short period of few weeks after beetle emergence.     

Pathogens of the bark beetle Ips cembrae: microsporidia and gregarines also known from other Ips species

The objective of the current study was to identify pathogens of the large larch bark beetle, Ips cembrae, which is a secondary pest that has produced several local outbreaks across Europe in recent years. Beetles were collected from pheromone traps, trap trees and emergence traps (Larix decidua) during 2007 to 2011 at 10 study sites in central Europe. A total of 3379 mature and callow beetles were examined with a light microscope, and only two microsporidian pathogens [Chytridiopsis typographi and a diplokaryotic microsporidium (probably Nosema sp.)] and two gregarines (Gregarina typographi and Mattesia schwenkei) were found. Within the I. cembrae populations, the infection rate for C. typographi ranged from 2 to 58%. Nosema sp. occurred in only two beetles in 2007 (at two study sites). G. typographi was recorded only in Austria and Croatia and only in 1–2% of the beetles in those countries. Mattesia schwenkei was observed solely in Croatia in 0.6% of the beetles in that country. Only one fungal pathogen in the genus Fusarium was found and only in two mature beetles (0.7%) in 2010. The pathogen species found during our study of I. cembrae were very similar to the pathogens previously identified for Ips typographus. No species‐specific pathogen was detected.     

Mortality pattern and age structure in two carabid populations with different seasonal life cycles

1. Adult populations of two carabid species, a spring breeder, Carabus yaconinus, and an autumn breeder, Leptocarabus kumagaii, were studied in a lowland habitat (area: 16,500 m²) by pitfall sampling and mark-recapture method. The seasonal change in population number, age structure and mortality pattern were clarified and related to their seasonal life cycles.
2. The survival rate of new adults from emergence to the first reproductive season was on the average 48% in C. yaconinus and 55% in L. kumagaii. In C. yaconinus, beetles which emerged later in the season survived more to the first reproductive season than those emerged earlier. C. yaconinus which had survived the pre-reproductive period mostly died out during the first reproductive season of 5 months, and about 8% survived until the second season. In L. kumagaii which had a short reproductive period in autumn, about 20% survived to the second reproductive season, and a small proportion even to the third reproductive season. Accordingly, the proportion of old beetles in the reproductive population was higher in L. kumagaii than in C. yaconinus.
3. The reproductive population of C. yaconinus contained on the average 1600 beetles and produced 3300 new adults. the L. kumagaii population contained on the average about 530 reproductives in autumn, and about 820 beetles emerged in the following year. The recruitment rate of new adults of C. yaconinus was higher than that of L. kumagaii, and this resulted in its higher population density. In L. kumagaii, however, the high adult survivorship and iteroparous reproduction were important for its population growth.
4. Relationship between seasonal adaptation and demographic strategies in the carabid populations were discussed.