Arthropod predation limits the population density of an herbivorous lady beetle,Henosepilachna niponica (Lewis)

1. The possible impact of arthropod predation on inter-population variation in adult density of a thistle-feeding lady beetle, Henosepilachna niponica (Lewis ) was evaluated by means of predator exclusion experiments conducted in the field.
2. The population density of newly-emerged adults at one habitat in the upstream area (site F) was significantly lower than at another in the downstream area (site A) although the egg density was nearly identical in the two habitats.
3. In the habitat with lower adult density, egg mortality was higher due to higher levels of predation. A predator exclusion experiment demonstrated that arthropod predation was the main factor causing high mortality during the immature stages, and physical factors such as heavy rains were unlikely to influence larval survivals.
4. Earwigs, ground beetles, predaceous stink bugs, and spiders were identified as the main predators in the study area. Of these, an earwig, Anechura harmandi (Burr ) was more predominant than other predators and was significantly more abundant in the habitat with low adult densities.

     

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

Population Ecology -     

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

1. A field study was carried out on the population dynamics of a thistle-feeding lady beetle, Henosepilachna pustulosa (Kôno ) living in a cool temperature climax forest in northern Kyoto Prefecture, central Japan.
2. Intensive marking, release and recapture program was carried out to estimate the adult population parameters by usingJolly-Seber method.
3. Sampling ratio was around 50%. Marking ratio rapidly rised as the census progressed and approached to 100%.
4. Sex ratio (% ♀) was 63–69% in both overwintered and new adults.
5. Daily survival rate was as high as 0.95 or more and constant throughout the season. Adult longevity in the spring was longer than 40 days.
6. Reproductive rate i. e., the ratio of the number of newly emerged adults in a given generation to that of overwintered adults in the preceding generation, is very small, ranging 1–3, whereas winter survival is higher than 50%, consequently the size of populations in the study area remain in a remarkably constant size and it never reached a level where intraspesific competition occurred.
7. The population characteristics of H. pustulosa are compared with those of the two closely related species, H. vigintioctopunctata and H. vigintioctomaculata, which are the pests of Solanaceous crops. Hp is more K-strategic than the two pest species.

     

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.

     

Limitation of reproduction by feeding condition in a carabid beetle,Carabus yaconinus

1. Effects of the amount of food consumed on reproduction of the carabid beetle, Carabus yaconinus B., were studied in the laboratory by rearing beetles at different food levels, and the feeding and oviposition rates in the field were estimated on the basis of the relationships between the amount of food consumed, body weight and egg production obtained in the experiment.
2. The maximum amount of food consumed was 150 mg of minced beef per day. The number of eggs laid per day and the mean body weight increased with an increase in the amount of food consumed. High mortality occurred only when the beetles consumed less than 25 mg of minced beef per day.
3. The ratio of current body weight to the minimum one just before death by starvation, W/W_min, was used for the estimation of the rates of food consumption and egg production. The relationships between mean W/W_min ratio, the amount of food consumed and the number of eggs laid per day were clarified.
4. The relationships between ovary states (ovary weight and the number of mature eggs in the ovary) and W/W_min ratio were examined for the females caught in the field. Females with higher values of W/W_min ratio had more mature eggs.
5. The amount of food consumed by females in the field during the reproductive period was estimated to be 50–70% of the maximum value attained in the experiment and the estimated rate of oviposition was 45–59% of the maximum rate attained in the experiment.

     

Continuous population estimates forDendroctonus frontalis Zimm. (Coleoptera: Scolytidae) occurring in infestations

Infestations of Dendroctonus frontalisZimm. are often observed to enlarge continuously by the colonization of new hosts in a pattern similar to a forest fire. This pattern of infestation growth presents unique problems in quantitatively estimating populations of D. frontalis. Beetle populations on each infested tree in an infestation go through five processes: attack, oviposition, reemergence, survivorship, and emergence. These processes, which have been described mathematically in the literature, each take several days for completion. In order to follow the distribution and abundance of D. frontalis throughout the course of development of a spot, we need a daily estimate of the number of beetles involved in each process on every tree. Since it is not practical to sample each tree daily, we developed a procedure whereby quantitative estimation procedures for within-tree populations were used in combination with the mathematical models for the life processes to produce a daily record of the number of adults successfully attacking trees, the number of eggs oviposited, the number of beetles reemerging, number of beetles surviving within the trees, and the number of beetles emerging. These daily estimates were then summarized for all trees in the spot for the duration of the infestation. The daily record of populations of D. frontalis, used with information on infestation geometry, were suggested to be of value in describing and elucidating several important facets of population dynamics including dispersal patterns within infestations, between tree beetle loss (mortality), and time lags among the various population processes. The information reported can be used to develop simulation models of population dynamics or to validate existing models.     

Factors affecting body size variation within a population of an herbivorous lady beetle,Henosepilachna niponica (Lewis)

Size variation in newly-emerged adults was examined in two different local populations of an herbivorous lady beetle, Henosepilachna niponica, for 1976–80. Mean adult size of both sexes changed rather synchronously in the two populations over 5 years. Body size of adult beetles apparently decreased with increasing leaf damage of the plants on which they developed. Adult beetles which emerged late in the season, associated with increasing food deterioration, were smaller than those which emerged early. Ecological consequences of adult size variation is discussed in terms of oviposition site selection.     

甲虫体内定居猪巨吻棘头虫微生态学初步研究

本文报告了１９８４年大连地区甲虫体内定居猪巨吻棘头虫的幼虫（棘头体）情况。大牙锯天牛的成虫定植率为１０．２％,低于１９７４年的３８．８％。本次调查发现铜绿丽金龟、蒙古丽金龟和灰粉锶金龟,共４种金龟体内都有棘头体定居,其定植率依次是２３．８％,２３．８％,１６．１％和３３．３％。前３种金龟体内定居着棘头体为大连地区首次报告。调查证明上述天牛和金龟６种甲虫也是本地区流行的猪巨吻棘头虫病的重要媒介,如采     

A dispersal-aggregation model for mountain pine beetle in lodgepole pine stands

In this paper a dispersal-attack theory for bark beetle attacking trees is developed from a set of simple assumptions, and the resulting theoretical model is fit to data from four epidemic studies. Implications of the theory are discussed in relation to the dynamics of lodgepole pine-mountain pine beetle interactions.     

Differences in temporal utilization patterns of dung pats among three scarabaeid dung beetles

1. Differences in the temporal utilization patterns of dung pats were investigated among three dung beetle species, Aphodius haroldianus, Onthophagus lenzii and Liatongus phanaeoides, and density effects of three species on emigration from a dung pat were compared.
2. A. haroldianus preferred fresh dung pats, immigrated to fresh pats and then emigrated from those pats quickly (mean duration of residence 48.4 h), whereas L. phanaeoides immigrated to older dung pats (over 7 days after deposition) as well as fresh ones and remained in the pats for the longest time (165.6 h).O. lenzii showed intermediate behavior in this respect (63.3 h).
3. In A. haroldianus, the presence of conspecifics induced faster emigration than presence of the other two species. L. phanaeoides showed the opposite relationship. In O. lenzii, the response to conspecifics was intermediate to those of the other two species.

     

Rostrum structure and development in the rice weevil Sitophilus oryzae (Coleoptera: Curculionoidea: Dryophthoridae)

A documentation and review of weevil rostrum growth is made through examination of the developmental life stages in the rice weevil Sitophilus oryzae (Linnaeus). Histological and morphological examinations are made utilizing light, fluorescent, and electron microscopy. In S. oryzae, rostral tissue begins proliferating in the late 4th instar larva and continues through to the pupal stage, with the majority of rostrum growth taking place in the prepupa. Adult cranial and rostral morphology is also reviewed, focusing on structures that may be pertinent to phylogeny reconstruction. The weevil rostrum is essentially an extension of various head sclerites that are basal to the mouthparts. Therefore, while the mouthparts are fairly similar to other Coleoptera in basic form, the head is markedly different due to its anterior extension. By understanding the more noticeable details of rostrum growth and structure, this study may serve as a foundation for comparative studies of a similar nature and as a basis for beginning research on the genetic nature of rostrum formation and evolution throughout the weevil clade.     

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     

Biogeography of the yeasts of ephemeral flowers and their insects

We studied specific yeast communities vectored by beetles, drosophilids, and bees that visit ephemeral flowers, mostly in the genus Hibiscus and in the families Convolvulaceae and Cactaceae, in the Neotropical, Nearctic, and Australian biogeographic regions. The communities consist mostly of yeasts in four clades centered around the genera Metschnikowia, Kodamaea, Wickerhamiella, and Starmerella. The largest geographic discontinuity occurs as a function of the nitidulid beetle species that dominate the non-pollinator insect visitors of the flowers. This partitions the New World, where the dominant beetle is in the genus Conotelus, from the Australian biogeographic region, dominated by species of Aethina. Distinct but sympatric insects may also carry radically different yeast communities.     

Modelling the effects of field spatial scale and natural enemy colonization behaviour on pest suppression in diversified agroecosystems

1. Diversifying agroecosystems by establishing or retaining natural vegetation in and around crop areas has long been recognized as a potentially effective means of bolstering pest control as a result of attracting more numerous and diverse natural enemies, although outcomes are inconsistent across species.
2. Little is known about the underlying mechanisms driving such differences in species responses, creating challenges for determining how best to manage landscapes for maximizing environmental services such as biological control.
3. The present study addresses gaps in our understanding of the link between noncrop vegetation in field margins and pest suppression by using a system of partial differential equations to model population‐level predator–prey interactions, as well as spatial processes, aiming to capture the dynamics of crop plants, herbivores and two generalist predators.
4. We focus on differences in how two predators (a carabid and a ladybird beetle) colonize crop fields where they forage for prey, examining differences in how they move into the fields from adjacent vegetation as a potential driver of differences in overall pest suppression.
5. The results obtained demonstrate that predator colonization behaviour and spatial scale are important factors with respect to determining the effectiveness of biological control.

     

Three new asexual arthroconidial yeasts, Geotrichum carabidarum sp. nov., Geotrichum histeridarum sp. nov., and Geotrichum cucujoidarum sp. nov., isolated from the gut of insects

Twenty arthroconidial yeasts were isolated from the digestive tract of basidiome-feeding beetles and lepidopteran larvae. All of the yeasts reproduced only asexually by arthroconidia and some by endo- or blastoconidia as well. Based on the comparisons of sequences in ribosomal RNA genes and other taxonomic characteristics, the yeasts were identified as three unknown Geotrichum species. The three new species are described as Geotrichum carabidarum (NRRL Y-27727^T), G. histeridarum (NRRL Y-27729^T), and G. cucujoidarum (NRRL Y-27731^T). Phylogenetic analyses from ribosomal DNA sequences showed that members of the genus Geotrichum and related arthroconidial yeast taxa were divided into two major clades: (1) Dipodascus and Galactomyces with Geotrichum anamorphs including all the new species; and (2) Magnusiomyces with Saprochaete anamorphs. G. cucujoidarum formed a subclade with G. fermentans and Geotrichum sp. Y-5419, while the two closely related species, G. carabidarum and G. histeridarum, represent a new basal subclade in the clade of Geotrichum and its teleomorphs.     

The elytra-to-body binding mechanism of the flightless rainforest species Tabarus montanus Kaszab (Coleoptera: Tenebrionidea)

The elytra-to-body binding mechanism of the flightless rainforest species Tabarus montanus Kaszab (Coleoptera: Tenebrionidea) is described. Previously, studies on this complex character system in tenebrionids have focused mostly on either fully-winged or flightless, desert-dwelling species with a hermetically sealed subelytral cavity. Data presented here show that the rainforest species Ta. montanus has permanently joined interlocking macrostructures between the two elytra along the midline and between the elytral epipleuron and the sides of the body. These are very similar adaptations to ones found in flightless desert tenebrionids. Frictional patches of microtrichia, previously reported in all wing-folding beetle suborders including flightless taxa, are completely absent in Ta. montanus. This constitutes the first report of the complete loss of frictional microtrichia patches in a beetle with fully-developed elytra. Sensory organs (hair sensilla), usually involved in the correct positioning of the elytra over the beetles’ body at rest are also absent in Ta. montanus. The significance of these results relating to the evolution of the tenebrionid subelytral cavity is discussed.     

Antifeedant Properties of Destruxins and their Potential Use with the Entomogenous Fungus Metarhizium anisopliae for Improved Control of Crucifer Pests

Destruxins A, B and E, produced by the entomogenous fungus Metarhizium anisopliae, are insecticidal but comparatively low doses have antifeedant properties. Treatment of cabbage leaf discs with destruxins significantly reduced feeding by larvae of Plutella xylostella and Phaedon cochleariae in both choice and no-choice assays. The Antifeedant Index (AI) was dose related and there were significant differences between treated and untreated leaves. The AI and acute toxicity assays suggest that insect death was due to a combination of the starvation and toxicity effects of destruxins. In whole plant experiments, adults and larvae of P. cochleariae were found to be more susceptible to infection by M. anisopliae V245 if it was used in conjunction with a crude destruxin mixture. Destruxins drove larvae off the plant, irrespective of which leaf surface was treated. Adults could be forced to the adaxial or abaxial surface of leaves using the crude destruxin. Mortality was usually more consistent and generally greater if adults were forced to abaxial than adaxial surfaces inoculated with the fungus. High humidity on the abaxial surface favoured conidia germination and infection. Mortality was also greater for adults dusted with the pathogen and forced to the abaxial rather than to the adaxial leaf surface. The increased movement and starvation associated with destruxin treatment may also have stressed the insects making them more susceptible to infection.     

Screening pigment,aperture and sensitivity in the dung beetle superposition eye

Summary Sensitivity to light was investigated in the refracting superposition eye of the dung beetle Onitis alexis using electrophysiological measurements and optical modelling. Intracellular recordings were made from single retinula cells over 24-h periods, with cells light and dark adapted, in order to measure the response/intensity (V-LogI) functions. The combined effects of a circadian rhythm and light adaptation allow the determination of the relative contributions of screening-pigment migration and transduction gain to changes in sensitivity in the eye. Between the extremes of dark adaptation at night and light adaptation during the day, the maximum sensitivity change possible is at least 4 log units, of which approximately 2 log units can be accounted for by changes in the transduction gain and at least 2 log units by screening-pigment migration. The role of the superposition aperture (the number of facets that contribute light to one rhabdom) in 3 species of dung beetle was investigated with an optical ray-tracing model of the eye. The facets of the superposition aperture do not contribute light equally to the target rhabdom; except in one species, the greatest contribution comes from facets located away from both the centre and periphery of the aperture. Light adaptation increases the optical density of the superposition aperture and decreases its size.