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Results 1111 to 1140 of 2340:

Multicoloniality in the highly polygynous ant Crematogaster pygmaea (Formicidae: Myrmicinae)

Rachid HAMIDI, Gabriel DEBOUT, Ana HEREDIA, Denis FOURNIER, Yves QUINET, Jean-Christophe De BISEAU

Eur. J. Entomol. 109 (1): 95-102, 2012 | DOI: 10.14411/eje.2012.012

In social insects, the high variability in the number of queens per colony raises fundamental questions about the evolution of altruism. It is hypothesized, for instance, that nestmate recognition should be less efficient in polygynous than in monogynous colonies because the presence of several breeders increases the diversity of genetically determined recognition cues, leading to a less specific colonial signature. Recent studies, however, have shown that the link between the number of queens in a colony and the recognition abilities of its members is more complex than previously suggested. Here, we studied intraspecific aggression, diversity of potential recognition cues and genetic structure of colonies in the highly polygynous ant Crematogaster pygmaea. Our results reveal that workers of this species are clearly aggressive towards non-nestmates in field experiments but not in more artificial bioassays conducted in Petri dishes, underscoring the importance of context-dependent aspects of the assessment of nestmate recognition. Behavioural, genetic and chemical data show that C. pygmaea is a multicolonial species, forming spatially restricted and well-defined entities. Therefore, the postulated negative correlation between recognition ability of workers and queen number in a colony is not supported by the results of this study.

Bumblebee (Hymenoptera: Apidae) sample storage for a posteriori molecular studies: Interactions between sample storage and DNA-extraction techniques

António S. MOREIRA, Finbarr G. HORGAN, Tomás E. MURRAY, Thomais KAKOULI-DUARTE

Eur. J. Entomol. 110 (3): 419-425, 2013 | DOI: 10.14411/eje.2013.056

A global decline in pollinator abundance and diversity has demanded increased research attention to the ecology and genetics of bumblebees. However, as progressively more restrictions are placed on sampling for insects, researchers are increasingly obliged to use archival specimens collected for purposes other than genetic analyses. In this study we assessed the suitability, for population genetic studies, of popular, low-cost methods for preservation and storage of bumblebee specimens. Specimens of Bombus terrestris L. were held under six storage regimes for up to two years. DNA was extracted from the samples using three extraction protocols and the quality of the DNA was examined using PCR amplification of a mitochondrial and a nuclear gene. All extraction and storage methods provided sufficient DNA for successful PCR amplification. However, samples preserved in acetone or at freezing temperatures yielded the highest DNA concentrations. DNA yields from pinned specimens at room temperature declined over time, particularly when using standard extraction techniques. DNA concentrations were significantly lower from specimens preserved in 70% ethanol compared to all other extraction techniques and declined linearly over the two years of storage. These results indicate that two of the most popular insect storage methods (pinning and storage in ethanol) should be avoided for the long-term preservation of genetic material for future studies. We suggest that optimal insect preservation methods should be incorporated into research protocols in order to best capitalise on limited collection opportunities.

Preference of larvae of Enallagma cyathigerum (Odonata: Coenagrionidae) for habitats of varying structural complexity

Ralf C.M. VERDONSCHOT, Edwin T.H.M. PEETERS

Eur. J. Entomol. 109 (2): 229-234, 2012 | DOI: 10.14411/eje.2012.030

In macrophyte-rich lentic ecosystems, higher numbers of damselfly larvae occur in areas where there is structurally complex vegetation than in those where the plant architecture is relatively simple. Biotic interactions rather than morphological constraints are considered to underlie this pattern. We investigated whether the preference of the larvae of the damselfly Enallagma cyathigerum for a particular habitat was retained in absence of prey, predators and/or conspecifics. A series of laboratory choice experiments was conducted in which combinations of sediment and artificial plants differing in structural complexity were offered simultaneously to the larvae. Larvae preferred patches with structurally complex vegetation over patches with simply structured vegetation or lacking vegetation. Patches with simply structured vegetation were preferred over those with bare sediment, but the number of larvae showing a clear choice, which is regarded as an indication of the strength of the preference for a particular habitat, was relatively low compared to the number of individuals responding when complex vegetation was present. Based on the results presented, we conclude that the preference of E. cyathigerum larvae for structurally complex vegetation is independent of the presence of predators, prey or competitors. This suggests that this behaviour of the larvae is either learned or an innate response.

BOOK REVIEW: Karjalainen S. & Hämäläinen M. 2013: Demoiselle Damselflies: Winged Jewels of Silvery streams.

R. KHELIFA

Eur. J. Entomol. 110 (4): 703, 2013 | DOI: 10.14411/eje.2013.094

Karjalainen S. & Hämäläinen M. 2013: Demoiselle Damselflies: Winged Jewels of Silvery streams. Caloptera, Helsinki, 223 pp. (bilingual, Finnish and English). ISBN 978-952-93-1045-6. Price EUR 36.00 (hardcover).

BOOK REVIEW: Lancaster J. & Briers R.A. (eds) 2008: Aquatic Insects: Challenges to Populations. Proceedings of the Royal Entomological Society's 24th Symposium.

D. BOUKAL

Eur. J. Entomol. 110 (3): 544, 2013 | DOI: 10.14411/eje.2013.073

Lancaster J. & Briers R.A. (eds) 2008: Aquatic insects: challenges to populations. Proceedings of the Royal Entomological Society's 24th symposium. Cab International, Wallingford, UK, x + 332 pp. ISBN 978-1-84593-396-8. Price GBP 85.00, USD 170.00, EUR 135.00.

Population structures of three Calliptamus spp. (Orthoptera: Acrididae) across the Western Mediterranean Basin

Elodie BLANCHET, Michel LECOQ, Gregory A. SWORD, Christine PAGES, Laurence BLONDIN, Claire BILLOT, Ronan RIVALLAN, Antoine FOUCART, Jean-Michel VASSAL, Ange-Marie RISTERUCCI, Marie-Pierre CHAPUIS

Eur. J. Entomol. 109 (3): 445-455, 2012

We conducted a comparative population genetic analysis of levels of genetic variation and its geographical structuring in three closely related species of grasshopper that co-occur in the Mediterranean Basin: Calliptamus italicus, C. barbarus and C. wattenwylianus. In the western part of their distributions 5 populations of C. italicus, 13 of C. barbarus and 10 of C. wattenwylianus were sampled. Bootstrap re-sampling of populations and microsatellite loci within each species indicated a lower level of genetic diversity and higher level of genetic differentiation in C. barbarus, which is less of an outbreak pest species than either of the other Calliptamus species studied. This may be due to lower effective sizes of non-outbreak populations and/or lower gene flow among them.

Pollination of Sedirea japonica (Orchidaceae) by Bombus diversus diversus (Hymenoptera: Apidae)

Kenji SUETSUGU, Koji TANAKA

Eur. J. Entomol. 110 (3): 545-548, 2013 | DOI: 10.14411/eje.2013.074

There are no records of the pollinators of many orchids even though the Orchidaceae are often cited as the example of an intimate relationship between plants and their pollinators. We recorded the insects visiting the flowers of Sedirea japonica that might be pollinators of this species by using digital cameras to take photographs automatically of the flowers. Based on our evidence of pollinia being attached or removed from flowers, we conclude that Sedirea japonica can be pollinated by Bombus diversus diversus.

Stable isotopes reveal dietary divergence between dispersal phenotypes in Tetrix subulata pygmy grasshoppers (Orthoptera: Tetrigidae)

Einat KARPESTAM, Anders FORSMAN

Eur. J. Entomol. 110 (1): 65-70, 2013 | DOI: 10.14411/eje.2013.008

In some species of insects, individuals with fully developed wings and capable of flying coexist with flightless individuals that lack functional wings. Their diets may differ if long-winged individuals are more mobile and therefore likely to be better at finding and utilizing high quality food resources, or if they have different food preferences or physiological requirements. Despite its potential importance, differences in the diet of dispersal phenotypes have not been unequivocally demonstrated under natural conditions. To test for dietary divergence, we compared natural abundances of carbon and nitrogen stable isotope ratios (d13C and d15N) in long- and short-winged free ranging Tetrix subulata pygmy grasshoppers collected as adults from two natural populations. Overall, this comparison of stable isotopes indicated long-term differences in the diet of the two wing morphs in both populations, but not between males and females of the same morph. We conclude that it is likely that the dietary niches of the long winged and flightless individuals differ under natural conditions. This may reduce intra-specific competition, offset the expected trade-off between flight capacity and reproduction and promote ecological speciation.

Biological and distributional overview of the genus Eledonoprius (Coleoptera: Tenebrionidae): Rare fungus-feeding beetles of European old-growth forests

Giuseppe M. CARPANETO, Stefano CHIARI, Paolo A. AUDISIO, Piero LEO, Andrea LIBERTO, Nicklas JANSSON, Agnese ZAULI

Eur. J. Entomol. 110 (1): 173-176, 2013 | DOI: 10.14411/eje.2013.025

All the information on the genus Eledonoprius was gathered to provide an up to-date overview of the geographical distribution and ecology of its species, and to assess their association with old-growth forests. Based on recent samples collected in deciduous forests and woodlands of Italy, the authors outline the habitats of these rare species and give an account of their trophic relations with bracket fungi. E. armatus is recorded in Central Italy and Sardinia for the first time; E. serrifrons is new to Basilicata (Southern Italy) and Syria.

Larval morphology of Scydmaenus tarsatus and S. hellwigii, with notes on feeding behaviour and a review of the bibliography on the preimaginal stages of ant-like stone beetles (Coleoptera: Staphylinidae: Scydmaeninae)

Pawe³ JA£OSZYÑSKI, Aleksandra KILIAN

Eur. J. Entomol. 109 (4): 587-601, 2012 | DOI: 10.14411/eje.2012.073

Morphology of mature larvae of two Central European species of Scydmaenus Latreille is described and illustrated: S. (s. str.) tarsatus Müller & Kunze and S. (Cholerus) hellwigii (Herbst). Inaccuracies in previous descriptions of S. tarsatus are discussed and the following combination of characters is defined as diagnostic for Scydmaenus: epicranial sutures reaching posteromedian margins of antennal insertions; presence of a single pair of stemmata and epicranial supraantennal pits; anterior row of subtriangular teeth on epipharynx; mandibles falciform and without mesal teeth; antennomere 3 rudimentary; antennal sensory appendage subconical and asymmetrical; maxilla with galea and lacinia; labium strongly constricted between mentum and prementum; thoracic tergites undivided along midline; head capsule, thoracic tergites, laterotergites and abdominal segments except sternite 1 densely setose; thoracic sternites and abdominal sternite1 largely asetose; and lack of urogomphi. We also describe the feeding behaviour of immature S. tarsatus and demonstrate for the first time that Scydmaeninae larvae can feed on live springtails and not armoured mites. In the introduction we provide a summary of the literature on all hitherto known preimaginal stages of Scydmaeninae.

BOOK REVIEW: Stockmann R. & Ythier E. 2010: Scorpions of the World

Franti¹ek ©«ÁHLAVSKÝ

Eur. J. Entomol. 110 (3): 400, 2013 | DOI: 10.14411/eje.2013.053

Stockmann R. & Ythier E. 2010: Scorpions of the World. N.A.P. Editions, Verrières-le-Buisson, 565 pp. ISBN 978-2913688117. Price GBP 68.00.

Occurrence of arrhenotoky and thelytoky in a parasitic wasp Venturia canescens (Hymenoptera: Ichneumonidae): Effect of endosymbionts or existence of two distinct reproductive modes?

Vincent FORAY, Hélène HENRI, Sonia MARTINEZ, Patricia GIBERT, Emmanuel DESOUHANT

Eur. J. Entomol. 110 (1): 103-107, 2013 | DOI: 10.14411/eje.2013.014

Endosymbiotic organisms are known to manipulate the reproductive biology of their hosts. Incomplete prevalence of endosymbiont inducing thelytokous parthenogenesis results in the coexistence of sexual and asexual individuals, and could account for the maintenance of sexual reproduction in certain populations or species. In the parasitoid Venturia canescens, arrhenotokous ("sexual") and thelytokous ("asexual") individuals occur sympatrically. We aimed to determine whether endosymbionts are implicated in the thelytoky of V. canescens. After screening females of the two reproductive modes for several reproductive parasites: bacteria (Wolbachia, Rickettsia, Bacteroidetes, Spiroplasma, Arsenophonus) and Microsporidia, we concluded that thelytoky in V. canescens is not induced by any of these parasites and confirmed its suitability as a biological model for solving the evolutionary enigma of the maintenance of sexual reproduction.

Attraction to light - from how far do moths (Lepidoptera) return to weak artificial sources of light?

Christine TRUXA, Konrad FIEDLER

Eur. J. Entomol. 109 (1): 77-84, 2012 | DOI: 10.14411/eje.2012.010

Moths are frequently used as indicators of biodiversity or habitat quality. Light traps are the most effective and widely used method for gathering data on moth communities. Knowing the distance from which moths are drawn to a light trap is therefore essential for the ecological interpretation of such data. Two community-wide mark-release-recapture experiments were carried out in forest habitats in central Europe in order to investigate whether the percentage of marked moths recaptured at weak artificial light sources (2 × 15 W UV-light tubes) is dependent on the distance they were released from the light source. Altogether 2,331 moths belonging to 167 species were caught at light traps and released at distances of 2-100 m. Of these moths 313 returned to the light trap within 5 min of release. Percentage recapture was generally low (gross rate 13.4%) and strongly decreased with increase in the distance at which they were released. Percentage recapture was not significantly affected by ambient temperature or the sex of the moths. Only for the Geometroidea was the percentage recaptured slightly greater for the larger species. We found no significant differences between moth super-families with regard to the distance dependence of their attraction to light. Our data confirm that the radius of attraction of low powered light traps for moths is very small often even below 10 m. Thus, moths are good indicators of habitat quality and fragmentation as they are rarely attracted from distant habitats to such light traps.

Coccinellidae captured in blacklight traps: Seasonal and diel pattern of the dominant species Harmonia axyridis (Coleoptera: Coccinellidae)

Christine A. NALEPA

Eur. J. Entomol. 110 (4): 593-597, 2013 | DOI: 10.14411/eje.2013.080

Two blacklight traps were operated in a non-agricultural setting in Cary, North Carolina, USA, from spring through fall in 2004 and 2005 and all Coccinellidae collected and identified. More than 1300 lady beetles were collected in each of the two years, with Harmonia axyridis dominant (> 98%) and collected consistently over the course of the trapping period. Although other coccinellid species were observed in the vicinity of the traps during photophase, their appearance in blacklight traps was negligible. Harmonia axyridis exhibited a distinct diel periodicity in appearance at the traps, beginning approximately an hour after sunset and ending about midnight. Sunrise and sunset collections from flight interference and sticky traps in a local alfalfa field suggest that H. axyridis may be more flight active during the scotophase than Coleomegilla maculata, Hippodamia convergens, and Coccinella septempunctata. This study supports the suggestion that blacklight traps give a biased depiction of coccinellid species composition in a given area, and indicates that seasonal and circadian thresholds for flight activity, phototaxis, or both in H. axyridis may diverge from those in most other Coccinellidae.

Role of leaf mines in host location and pupation in Diglyphus isaea (Hymenoptera: Eulophidae)

De Yu ZOU, Hong Yin CHEN, Li Sheng ZHANG

Eur. J. Entomol. 109 (3): 373-379, 2012

Diglyphus isaea Walker (Hymenoptera: Eulophidae) is an important ectoparasitic wasp of many leaf miners. Ability of D. isaea to find hosts placed in artificial mines and for its larvae to pupate when the larva is not in a mine was studied. Artificial mines consisted of slits cut in index card sandwiched between two cover slips. Almost 80% of the neonate larvae of D. isaea located host larvae in artificial mines compared to only 50% of those not in a mine. Mature larvae removed from mines did not construct normal pupal chambers. Nonetheless, they pupated and emerged successfully. Larvae of Liriomyza sativae Blanchard (Diptera: Agromyzidae) in mines are more likely to be attacked than those not in mines. Moreover, when close to a host larva this parasitoid can use vibrational cues to locate the larva in a mine. In addition, this parasitoid also did not always use volatile and gustatory cues for short range location of hosts. However, adult females of D. isaea more quickly located L. sativae larvae in the presence of the odour of juice extracted from an uninfested host plant. We conclude by proposing that the host mine is the medium by which the vibrations generated by the host larva are transmitted, which are probably the most important cue used by female D. isaea searching for hosts. That is this parasitoid first perceives mines not host larvae. These results will be helpful for developing techniques for the mass rearing of D. isaea in the future.

Are macrophyte-dwelling Chironomidae (Diptera) largely opportunistic in selecting plant species?

Mónika TÓTH, Arnold MÓRA, Béla KISS, György DÉVAI, András SPECZIÁR

Eur. J. Entomol. 109 (2): 247-260, 2012 | DOI: 10.14411/eje.2012.033

In this study we evaluate how variations in taxonomic composition and physical structure of macrophyte stands affect plant-dwelling chironomid assemblages in highly variable macrophyte assemblages in two densely vegetated backwaters. By using multivariate explanatory techniques we found that similar vegetation composition did not unequivocally relate to similar chironomid assemblages, moreover the diversity of macrophyte stands did not correlate with the taxonomic diversity of chironomid assemblages in the backwaters investigated. Taxonomic composition and structural characteristics of the vegetation had little influence on the taxonomic or functional (i.e. feeding groups) composition of chironomid assemblages inhabiting them. Similarly, there are only weak relationships between the distribution of certain chironomid species or functional feeding groups and the environmental variables investigated. In general, the structure of the vegetation was more closely associated with the distribution of dominant chironomid taxa than compositional variables (i.e. density of specific macrophyte taxa). In summary, the structure of aquatic vegetation (i.e. position, size of a stand of vegetation, total plant density) and characteristics of the environment where it develops may be more important in shaping plant-dwelling chironomid assemblages than the taxonomic composition of the vegetation.

Correlated traits for dispersal pattern: Terrestrial movement of the water cricket Velia caprai (Heteroptera: Gerromorpha: Veliidae)

Tomá¹ DITRICH, Miroslav PAPÁÈEK

Eur. J. Entomol. 106 (4): 551-555, 2009 | DOI: 10.14411/eje.2009.069

Macropterous individuals of wing polymorphic semiaquatic bugs (Heteroptera: Gerromorpha) usually occur at a high frequency if there is a need to leave an unfavorable habitat or in a generation migrating to/from an overwintering site. Velia caprai (Veliidae) is usually found in unpredictable habitats, but the macropterous morph is rare. Laboratory, mesocosm and field experiments were used to test the hypothesis that individuals of this species migrate by walking rather than by flight. Laboratory experiments that focused on the development of macropterous morph under conditions that usually stimulate the development of this morph in water striders were unsuccessful. A high temperature shortened the duration of nymphal development, but no winged specimens of Velia caprai developed in the laboratory when reared under either high or low temperatures, long or short photoperiods or on the surface of water or wet filter paper. Mesocosm experiments with apterous adults revealed they are able to walk on land. Both the males and females dispersed by walking in semi-natural conditions. Long-term field experiments using mark and recapture confirmed that this species can disperse by walking. Apterous individuals can compensate for downstream drift by upstream terrestrial migration and colonize newly established pools and ditches even several tens of meters from source sites. The development of a macropterous morph in response to environmental factors is replaced by terrestrial dispersal in V. caprai.

Potential role of hydrogen peroxide and melanin in the cold hardiness of Ostrinia nubilalis (Lepidoptera: Pyralidae)

Danijela KOJIC, Ivan SPASOJEVIC, Milo¹ MOJOVIC, Du¹ko BLAGOJEVIC, M. Roger WORLAND, Gordana GRUBOR-LAJSIC, Mihajlo B. SPASIC

Eur. J. Entomol. 106 (3): 451-454, 2009 | DOI: 10.14411/eje.2009.056

The aim of this study was to investigate the relationship between antioxidant enzymes and reactive oxygen species production in diapausing larvae of the European corn borer, Ostrinia nubilalis (Lepidoptera: Pyralidae) kept at 5°C, -3°C and -16°C for two weeks. The amount of hydrogen peroxide (H2O2), activity of antioxidant enzymes, copper zinc superoxide dismutase (CuZnSOD), manganese superoxide dismutases (MnSOD) and catalase (CAT) in whole body homogenates, as well as the electron paramagnetic resonance (EPR) spectroscopy of this insect's whole body were analysed. A higher level of melanin radical and lower CuZnSOD and CAT activities were found in larvae kept at -3°C than at 5°C and -16°C. At the same temperature (-3°C) an elevated H2O2 concentration was recorded. A possible regulatory role of H2O2 at -3°C, which is the temperature that triggers freezing tolerance, is suggested.

Regulation of the development of flight muscles in long-winged adults of the flightless bug Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae)

Radomír SOCHA, Jan ©ULA

Eur. J. Entomol. 105 (4): 575-583, 2008

We studied the development of the indirect flight muscles and reproductive organs in long-winged (macropterous) adults of the flightless bug Pyrrhocoris apterus (L.) and the factors involved in flight muscles histolysis by means of total protein analysis. Both the extirpation of the corpus allatum, an endocrine gland that is the sole source of juvenile hormone, and sham operation accelerated histolysis and decreased the level of the total protein content of the flight muscles to the same extent. Degeneration of flight muscles was not a result of allatectomy but rather a consequence of injury, followed by resumption of enhanced food intake, because it was stimulated also by the removal of wings. Transfer of penultimate instar larvae to a diapause-inducing short-day photoperiod did not prevent imaginal growth and histolysis of flight muscles, but inhibited growth of ovaries in females and maturation of accessory glands in adult males. Thus inactivation of the corpus allatum in diapausing macropters does not prevent imaginal growth of their flight muscles. Application of a high dose of methoprene to the surface of intact long-day macropterous adults induced precocious histolysis of flight muscles and growth of ovaries in females and accessory glands in males. Prolonged starvation of macropterous adults had only a small effect on the histolysis of their flight muscles. The results indicate that imaginal growth and histolysis of indirect flight muscles in macropterous individuals of P. apterus are largely juvenile hormone-independent processes that are programmed to occur spontaneously, but can be affected by various internal and external factors.

Forgotten natural enemies: Interactions between coccinellids and insect-parasitic fungi

Helen E. ROY, Ted E. COTTRELL

Eur. J. Entomol. 105 (3): 391-398, 2008 | DOI: 10.14411/eje.2008.049

The role of predators and parasitoids in the regulation of insect populations is widely reported in the context of both pest and non-pest insects. However, this is not the case for pathogens (entomopathogens). Indeed, most studies on insect life history refer only to predators and parasitoids when considering natural enemy guilds, even though naturally occurring entomopathogens are undoubtedly more diverse and widespread. This is certainly the case with the Coccinellidae; the natural enemies of coccinellids have been the subject of a number of review articles but pathogens receive only brief mention. In this review we attempt to address the balance and consider the interactions of natural populations of Coccinellidae with entomopathogenic fungi. Most research on entomopathogens and Coccinellidae focuses on the non-target impact of biorational insecticides against coccinellids and the impact of fungal infections upon aggregations of overwintering coccinellids; with the former overwhelmingly dominating the literature. Given the prominence of coccinellids in classical and conservation biological control, it is surprising that studies have not measured the natural impact of pathogenic fungi upon introduced species or natural populations of Coccinellidae, as has been done with numerous insect pest species. Here we review the literature on the intriguing interactions between coccinellids and fungal pathogens. We examine the literature on direct infection (sub-lethal and lethal) of coccinellids by pathogenic (Beauveria bassiana, Metarhizium anisopliae, Paecilomyces fumosoroseus) or parasitic (Hesperomyces virescens). We also consider the role of intra-guild predation (on the aphid-specific fungus Pandora neoaphidis and Beauveria bassiana) and finally indirect interactions such as coccinellids dispersing P. neoaphidis. We suggest that fungal pathogens are all too often forgotten natural enemies and future research should address the profound absence of knowledge in this field.

A landscape view of cereal aphid parasitoid dynamics reveals sensitivity to farm- and region-scale vegetation structure

Michael J. BREWER, Takuji NOMA, Norman C. ELLIOTT, Alexandra N. KRAVCHENKO, Ann L. HILD

Eur. J. Entomol. 105 (3): 503-511, 2008 | DOI: 10.14411/eje.2008.066

Functioning of plant-aphid-natural enemy interactions may be associated with the structure and composition of withinfield vegetation, neighborhood fields and field borders, and the regional plant community of cropped and noncropped areas. Farmand region-scale vegetation in the wheat-growing area of the North American Great Plains was hypothesized to effect the abundance of two hymenopteran parasitoids, that differ in physiological and behavioral attributes, of the key pest aphid of wheat, Diuraphis noxia (Mordvilko). The parasitoids had greater sensitivity to farm-scale vegetation (wheat strip rotation with or without spring-sown sunflower) than region-scale vegetation (degree of diversification with other crops and wheat fields converted to conservation grasslands). A two-way factorial design of scale (farm- and region-scale) revealed that parasitoid abundance in grass-dominant (homogeneous) areas especially benefited from adding sunflower to the wheat-fallow strip crop rotation. Considerable sensitivity of the analysis was added when adjusting for seasonality of vegetation, revealing that the region-scale effects were most prominent late season. From a management viewpoint, adding sunflower into the wheat production system, especially in relatively homogeneous vegetation regions, tends to promote local parasitoid populations during the summer when spring-sown plants are maturing and wheat is not in cultivation. Contrasting results for A. albipodus and L. testaceipes were consistent with expectations based on behavioral and physiological attributes of the two aphid parasitoid families they represent. Still, the general management interpretation seems robust for the two parasitoids and has relevance to both farm- and region-scale management schemes that are occurring in the wheat production zone of North American Great Plains.

Female reproductive patterns in the millipede Polydesmus angustus (Diplopoda: Polydesmidae) and their significance for cohort-splitting

Jean-François DAVID

Eur. J. Entomol. 106 (2): 211-216, 2009 | DOI: 10.14411/eje.2009.027

First-stadium juveniles of Polydesmus angustus born each month from May to September were reared throughout their life cycle under controlled seasonal conditions. At maturity, the reproductive patterns of 62 females were studied individually. It was confirmed that females born from May to August have a 1-year life cycle and those born from late August onwards a 2-year life cycle (cohort-splitting). A third type of life cycle - interseasonal iteroparity - was observed in a few females born late in the season. On average, annual females started to reproduce when 11.4 months old and produced 3.6 broods per female over 1.8 months; the later they were born from May to August, the later they reproduced the following year. Biennial females started to reproduce when 19.9 months old and produced 3.8 broods per female over 2.2 months; all reproduced early in the breeding season. These results indicate that only annual females can produce an appreciable proportion of biennial offspring from late August onwards, which rules out direct genetic determination of life-cycle duration. The reproductive characteristics of P. angustus suggest a non-genetic mechanism that can drive cohort-splitting. Because individual females reproduce for about 2 months on average, this automatically results in cyclic variation in life-cycle duration (annual/biennial/annual) in the long-term progeny of any female.

Agricultural policy-induced landscape changes: effects on carabid abundance and their biocontrol potential

Olga AMEIXA, Pavel KINDLMANN

Eur. J. Entomol. 105 (3): 467-476, 2008 | DOI: 10.14411/eje.2008.060

One of the most important services provided by biodiversity is thought to be the biological control of pests in agricultural landscapes, including aphids on cereals. The food webs potentially contributing to biological control of aphids primarily consist of polyphagous predators, parasitoids and pathogens. The problems of aphid pests have increased greatly since the 1970-ies, possibly as an effect of agricultural intensification, which is thought to have reduced diversity and abundance of these predators and parasites and consequently their biocontrol potential. The main objective of this study was to test this by measuring this potential for biological control of aphids, and relate it to agricultural intensification and predator abundance. We selected 30 farms distributed along agricultural intensification gradients, based on the amount of fertilizers applied per hectare. Estimates of ground-living predator density were obtained using pitfall trapping over a one-week period. Traps were placed inside the cereal fields, 10 m from the margin, in 2 replicates per field. Predation risk due to ground-living predators (biocontrol potential) was estimated by monitoring removal of aphids glued to labels. This was done in the same fields, in the immediate vicinity of the traps, over a period of 2 days. The proportion of aphids eaten per unit time was the response variable. We present the correlations between intensity of agricultural exploitation, predator abundance and biocontrol potential. The outcomes are not straightforward in that intensification begets a reduction in predator density and biocontrol potential. We discuss the potential confounding issues that might have affected our results.

Down-regulation of gene expression between the diapause initiation and maintenance phases of the Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae)

George D. YOCUM, Joseph P. RINEHART, Marnie L. LARSON

Eur. J. Entomol. 106 (4): 471-476, 2009 | DOI: 10.14411/eje.2009.059

The diapause initiation and maintenance phases of the Colorado potato beetle, Leptinotarsa decemlineata, were screened. Eight transcripts were found to be downregulated as the beetles enter the diapause maintenance phase of diapause development after day 15 postemergence. These transcripts were also expressed in early nondiapausing adults. Using BlastX, the transcripts were placed into six broad categories: regulatory (serpin), structural (apidermin), protease (serine protease), retinol binding protein (CRALBP), carbohydrate metabolism (ß-glucosidase, ß-mannosidase, and cellulose II), and unknown function.

Experimental evidence for density-determined wing dimorphism in two bush-crickets (Ensifera: Tettigoniidae)

Dominik PONIATOWSKI, Thomas FARTMANN

Eur. J. Entomol. 106 (4): 599-605, 2009 | DOI: 10.14411/eje.2009.075

Macroptery is common in many species of Orthoptera, but the causes are still discussed. Besides the assumption that macroptery is genetically determined, there is evidence that wing dimorphism is induced by environmental factors, particularly population density. However, most of the research is on pest species. In contrast, knowledge of wing dimorphism in species that occur at low population densites is still poor. Our study aims to test how density actually affects macroptery. As model organisms we chose two bush-cricket species of the genus Metrioptera (Ensifera: Tettigoniidae): While long-winged M. roeselii (Hagenbach, 1822) occur regularly, macropterous M. brachyptera (Linnaeus, 1761) are rare and are never observed outside their mating habitat. Nymphs of populations from the range core of both species (340 individuals each) were reared in groups of three and six individuals per 500 cm3 box, and individually. Our analyses revealed that development of macropters was mainly affected by the initial rearing densities. Compared with those reared individually the number of macropters was significantly higher among individuals reared at medium and high densities. The percentage of macropterous individuals was about twice as high in M. brachyptera as in M. roeselii, and the development of macropters significantly differed between the two species. These findings lead to the conclusion that macropterism is mainly influenced by density stress in both bush-crickets. Genetically determined wing dimorphism is unlikely, otherwise the observed high numbers of long-winged individuals of M. brachyptera, which are very rare under natural conditions, would never have developed in the laboratory. Macropterous M. brachyptera may rarely be found in the field, but we argue that this is due to low natural densities and, accordingly, to rare exposure to density stress.

Effect of female size on host selection by a koinobiont insect parasitoid (Hymenoptera: Braconidae: Aphidiinae)

Dionyssios LYKOURESSIS, Nikolaos GARANTONAKIS, Dionyssios PERDIKIS, Argyro FANTINOU, Andronikos MAUROMOUSTAKOS

Eur. J. Entomol. 106 (3): 363-367, 2009 | DOI: 10.14411/eje.2009.046

Body size is a main fitness component of insect parasitoids. We assessed the potential influence of maternal size of the parasitoid wasp Aphidius colemani Viereck (Hymenoptera: Braconidae: Aphidiinae) on its ability to parasitize the different instars of Aphis gossypii Glover (Hemiptera: Aphididae) on eggplant and cucumber. In the experiments "small" vs "large" parasitoid females were used. Females oviposited in all instars but more of the smaller hosts were parasitized. Host selection was affected by female size and the larger hosts were more frequently mummified by the large than the small females. Thus, parasitoid female size influenced host selection. This could affect the potential of the parasitoid to exploit populations of aphids that differ in their size structure. The importance of these results in terms of the ecological adaptations of the parasitoid and their implication for biological control are discussed.

Purification and characterization of a novel thermoacidophilic and thermostable α-mannosidase from the digestive fluid of oil palm weevil Rhynchophorus palmarum (Coleoptera: Curculionidae) larvae

Micaël BÉDIKOU, Pascal AHI, Martial KONÉ, Betty FAULET, Jean GONNETY, Patrice KOUAMÉ, Sébastien NIAMKÉ

Eur. J. Entomol. 106 (2): 185-191, 2009 | DOI: 10.14411/eje.2009.022

An extracellular α-mannosidase with unusual properties was purified from the digestive fluid of oil palm weevil (Rhynchophorus palmarum Linnaeus) larvae using ammonium sulphate saturation, size exclusion and anion-exchange chromatography. The enzyme named RpltM is thermoacidophilic, thermostable and behaves like lysosomal α-mannosidase (EC 3.2.1.24). The molecular weight, Km value, optimum reaction temperature and pH are 108-112 kDa, 0.36 mM, 65°C and 4.5, respectively. Zn2+ enhanced whereas Cu2+, Sodium dodecyl sulphate, swainsonine and 1,4-dideoxy-1,4-iminomannitol strongly inhibited its hydrolytic activity. The enzyme was stable for 25 min at 65°C and retained 70% of its initial activity after 60 min. At 70°C, around 60% of this activity was conserved after 25 min. RpltM retained more than 90% of its activity over a pH range of 4.2 to 5.0 and remained fully active in the presence of detergents such as nonidet P-40, triton X-100, polyoxyethylen-10-oleyl ether (up to 1%, w/v), dithiothreitol and β-mercaptoethanol. The stability under these conditions is also better than that reported for other insect α-mannosidases. Thus, RpltM could be used as an important bioindustrial tool for removing mannose residues from oligosaccharides.

Role of excreta in predator avoidance by the Kanzawa spider mite, Tetranychus kanzawai (Acari: Tetranychidae)

Keiko OKU

Eur. J. Entomol. 105 (4): 619-623, 2008

The Kanzawa spider mite, Tetranychus kanzawai (Acari: Tetranychidae) constructs webs over leaf surfaces and usually lives under these webs. T. kanzawai produces two types of excreta, black and yellow pellets, and uses its webs as a place for excretion. T. kanzawai also uses its webs as a refuge when the predatory mite, Neoseiulus womersleyi (Acari: Phytoseiidae) is present. To clarify what factors deter N. womersleyi from foraging on T. kanzawai webs, I experimentally examined the effects of T. kanzawai excreta on its own fitness (fecundity) and the foraging behaviour of N. womersleyi. When the excreta of T. kanzawai was put on leaf surfaces, the fecundity of T. kanzawai adult females was reduced by the black but not the yellow faecal pellets. On the other hand, predation by N. womersleyi was reduced by the yellow but not the black pellets. Although this effect of the yellow pellets on N. womersleyi did not last on leaf surfaces, it deterred N. womersleyi from staying on the web regardless of its freshness. These results suggest that T. kanzawai deposits black pellets on webs to avoid its negative effect on their own fitness, and yellow pellets are deposited on webs to reduce the risk of predation.

Revision of the genera Anisarthrocera, Rhampholyssa and Rhampholyssodes, description of the new genus Somalarthrocera and a phylogenetic study of the tribe Cerocomini (Coleoptera: Meloidae)

Federica TURCO, Marco A. BOLOGNA

Eur. J. Entomol. 105 (2): 329-342, 2008 | DOI: 10.14411/eje.2008.040

Four genera of the blister beetle tribe Cerocomini are revised, including the new genus Somalarthrocera. The genera Rhampholyssa Kraatz, 1863 and Somalarthrocera comprise two species each, whereas Anisarthrocera Semenow, 1895 and Rhampholyssodes Kaszab, 1983 are monotypic. S. savanicola sp. n. from Kenya is described, S. semirufa (Fairmaire, 1882) comb. n. is proposed, as well as new synonymy: A. batesi (Marseul, 1872) = A. batesi villiersi Kaszab, 1968. Phylogenetic relationships among the six genera of the tribe are defined by a cladistic analysis, which indicates three clades, one basal, represented by the genus Cerocoma Geoffroy, 1762, the second including Anisarthrocera and the pair Rhampholyssa and Rhampholyssodes, and the third including Diaphorocera Heyden, 1863 and Somalarthrocera. Bionomical information available for the four revised genera is summarised. Keys to these genera and to the species of the two non-monotypic genera are presented, as well as diagnoses of genera and species and catalogue of localities. Anisarthrocera is distributed in the northern Persian Gulf, Rhampholyssa in the Turanian depression, Rhampholyssodes is endemic to the eastern Arabian Peninsula, and Somalarthrocera is distributed in Somalia and Kenya. A brief biogeographical analysis of this primarily Palaearctic tribe is also presented.

Use of volatiles of Aristolochia chilensis (Aristolochiaceae) in host searching by fourth-instar larvae and adults of Battus polydamas archidamas (Lepidoptera: Papilionidae: Troidini)

Carlos F. PINTO, Alejandra J. TRONCOSO, Alejandro URZÚA, Hermann M. NIEMEYER

Eur. J. Entomol. 106 (1): 63-68, 2009 | DOI: 10.14411/eje.2009.010

Papilionid butterflies of the tribe Troidini are specialists on plants of the family Aristolochiaceae. The role of plant volatiles in host recognition by adult and larval stages of these insects remains unknown. We used Battus polydamas archidamas (Papilionidae: Troidini) and its host-plant, Aristolochia chilensis (Aristolochiaceae), to study: (i) the olfactory and electrophysiological responses of adults to headspace volatiles of the host-plant, (ii) the chemical composition of the headspace volatiles of the host-plant, (iii) the patterns of aggregation of larvae in the field in order to ascertain the time when they leave the plant where the eggs were laid, and (iv) the olfactory responses of solitary-feeding fourth-instar larvae to headspace volatiles of the host-plant. Larvae left their initial host-plant during the third or fourth instar. Host-plant headspace volatiles attracted fourth-instar larvae as well as adults; adult females were more responsive than males. Taken together, these results reveal changes in the responsiveness to host-plant volatiles during development, and provide an insight into the host-plant specialization of this butterfly.

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