Population dynamics of wireworms (Coleoptera,Elateridae) in arable land after abandonment

The community of elaterid larvae of three sites (field and two fallows), representing different stages of secondary succession, were studied using soil sampling from 1986 to 1993. All three sites were abandoned arable land: a field cultivated until 1991, a fallow I abandoned in 1986, and a fallow II abandoned about 1976. The fallow II was used as a meadow after abandonment and was regularly mown until 1985, when cultivation stopped. Six species of Elateridae larvae were found at all three study sites. In the field, Agriotes obscurus, Athous niger, Athous subsuscus, Dalopius marginatus and Athous vittatus were found, A. niger and A. obscurus being the most abundant species. During cultivation, larval densities were very low, however, larval abundance increased up to 8.8 ± 8.3 ind. m^-2 when cultivation stopped. Only small A. obscurus larvae were found during cultivation, whereas larval size increased after abandonment. In fallow I A. obscurus, A. niger, A. subsuscus, D. marginatus, and Agrypnus murinus were found and the average annual abundance fluctuated between 0.8 ± 1.4 to 40.8 ± 10.9 ind. m^-2 with A. obscurus being the most abundant species. Fallow II supported the highest densities of wireworms from all plots studied (71.2±35.2 to 280.0±24.8 ind. m^-2). A. obscurus, A. niger, A. subsuscus and D. marginatus were found in fallow II. The abundance of all larval Elateridae as well as the dominant species A. obscurus decreased during the study period, while simultaneously the occurrence of small sized A. obscurus larvae decreased. The frequency of cultivation and time elapsed since last cultivation appeared to be the most important factors affecting elaterid occurrence in the field and fallow I. In fallow II, the decrease in abundance correlates with the accumulation of a dense litter layer, which may correspond with soil surface structure, plant community changes or predator pressure.     

Stability of the microbial population in the gut of omnivorous wireworms (Coleoptera,Elateridae)

The variability of the microbial population structure of the gut of omnivorous wireworms Agriotes obscurus (L) and Selatosomus aeneus (L) was studied. The limits of intra- and interspecific and intersite variation were determined. The stability of the microbial composition of the gut allows us to reveal the list of obligate saprotrophs (with 95% probability) using only five replications. In the case of S. aeneus, the influence of starvation and diet change was studied. Starvation changed the microbial population structure, while the diet did not. The results confirm that omnivorous wireworms have a stable gut microbial population, which suggests an advanced mutualistic relationship between wireworms and their gut bacteria, possibly assisting in digestion and providing for ecological flexibility of wireworms.     

Transitional sublethal and lethal effects of insecticides after dermal exposures to five economic species of wireworms (Coleoptera: Elateridae)

During an insecticide toxicity study involving field-collected dusky wireworm, Agriotes obscurus (L.) (Coleoptera: Elateridae), wireworms exposed dermally to six classes of insecticides exhibited characteristic transitional symptoms of toxicity. These symptoms, collectively termed "morbidity," were categorized as "writhing," "leg and mouthpart movements," or "mouthpart-only body movements." These symptoms could persist for long periods, depending on insecticide and dose, with morbid wireworms ultimately recovering or dying. Additional LC50 and LD50 toxicity studies showed that these stages of morbidity also occurred in four other wireworm species, notably Agriotes sputator (L.), Limonius canus LeConte, Ctenicera pruinina (Horn), and Ctenicera destructor (Brown). In addition, all species exposed dermally to clothianidin moved in significant numbers to the surface of soil in posttreatment holding cups. This movement was not observed when these species were exposed to chlorpyrifos or the control solvent. These findings suggest that toxicity trials involving wireworms should include observations on morbidity, and the duration of trials should continue until symptoms of morbidity cease. The long-term morbidity and potential recovery or death of wireworms exposed to certain insecticides has implications for how laboratory and field studies can be better designed and interpreted in the future.     

Effects of neem seed derivatives on behavioral and physiological responses of the Cosmopolites sordidus (Coleoptera: Curculionidae)

Both in a choice and multi-choice laboratory tests, fewer adults of the banana root borer, Cosmopolites sordidus (Germar), settled under the corms of the susceptible banana "Nakyetengu" treated with 5% aqueous extract of neem seed powder or cake or 2.5 and 5% emulsified neem oil than on water-treated corms. Feeding damage by larvae on banana pseudostem discs treated with 5% extract of powdered neem seed, kernel, or cake, or 5% emulsified neem oil was significantly less than on untreated discs. The larvae took much longer to locate feeding sites, initiate feeding and bore into pseudostem discs treated with extract of powdered neem seed or kernel. Few larvae survived when confined for 14 d on neem-treated banana pseudostems; the survivors weighed two to four times less than the larvae developing on untreated pseudostems. Females deposited up to 75% fewer eggs on neem-treated corms. In addition, egg hatching was reduced on neem-treated corms. The higher the concentration of neem materials the more severe the effect.     

Repellency of a wireworm, Agriotes obscurus (Coleoptera: Elateridae), on exposure to synthetic insecticides in a soil-less bioassay

A soil-less bioassay arena to test repellency of wireworms (A. obscurus) to insecticides and carrier solvents is described. The bioassay and variables measured distinguish between shorter-range (contact and/or volatile) and longer-range (volatile) repellency. Wireworm positions are recorded every 3 s for 20 min, and average speed, rate of slowing, and longer- and shorter-range repellent behaviors calculated. Shorter-range repellency is determined with a Wireworm Repellency Score (WRS, range 0-100), calculated before contact and after contact with test chemicals. Of two carrier solvents tested, wireworms were strongly repelled by acetone (WRS = 57) but not by water (WRS = 1) when introduced to the bioassay arenas immediately after chemical inoculation. When bioassay arenas were assembled/sealed 2 min after inoculation, acetone elicited no repellency (WRS = 2). When dissolved in acetone in bioassays assembled with a 2-min delay, imidacloprid, chlorpyrifos, lindane, and tefluthrin elicited slight to moderate repellency at the highest concentrations tested (WRS = 30, 48, 42, and 49, respectively). Both longer- and shorter-range repellency increased over the duration of the observation period for lindane and tefluthrin, and shorter-range repellency also increased over the duration of the observation period for chlorpyrifos. Removal of volatiles in the bioassay arena by vacuum considerably affected wireworm movement in the arena, with the repellency elicited by acetone and lindane being significantly reduced. Clothianidin elicited no longer- or shorter-range repellency.     

华山松大小蠹对几种寄主挥发物组分的EAG和行为反应

为筛选适宜配制华山松大小蠹(Dendroctonus armandi)引诱剂的有效化学成分,用触角电位仪和Y型嗅觉仪测定了华山松大小蠹雌、雄虫对华山松挥发物主要成分的触角电生理(EAG)和行为反应.结果表明:在0.01、0.1、1、10、100 μg 5种刺激剂量下,7种化合物在特定浓度下均有明确的EAG反应;雌、雄虫对月桂烯、(+)-3-蒈烯、β-石竹烯3种化合物及雄虫对(+)-α-蒎烯、柠檬烯的EAG相对电位的最大值均出现在10μg刺激条件下;在10 μg刺激剂量条件下,雌虫对(+)-α-蒎烯、β-蒎烯和(+)-3-蒈烯有明显的正趋向反应,正趋向率均高于72%且显著高于雄成虫对3种挥发物的正趋向率;在1 μg刺激下,只有雄虫对(+)-3-蒈烯有一定正趋向反应;而在100μg条件下,(-)-α-蒎烯对雌、雄虫均有一定驱避作用.该研究结果可为开发华山松大小蠹林间引诱剂提供借鉴.     

Food habits of pasture wireworm,Conoderus exsul (Coleoptera: Elateridae)

Abstract

The food preferences and rates of growth of the omnivorous pasture wireworm, Conoderus exsul (Sharp) were studied. Larvae of soil-living insects were preferred to germinating maize seed, and wireworm growth rate was greater on insect compared with plant food. In glasshouse pot trials, wireworms increased their attack rate as the density of grass grub (Costelytra zealandica (White)) or white-fringed weevil (Graphthognathus leucoloma Boheman) larvae was increased. In field experiments that compared grass grub numbers in cages accessible to wireworms or protected from predators, predation varied with season from a low of 15% in late summer up to 82% in late autumn. White-fringed weevil larval mortality was increased by addition of wireworms in two field experiments, but not affected in a third trial where initial white-fringed weevil density was low. Grass grub mortality was increased by the presence of wireworms in field plots. Adult C. exsul were observed feeding on sweetcorn pollen.     

An investigation inot the use of multiple site characteristics to predict the presence and infestation level of wireworms (Agriotes sup., Coleoptera: Elateridae) in individual grass fields

Sixty-two grass fields were sampled in England and Wales over a three year period to assess the level of wireworm population present. Data on site-specific variables including soil physical characteristics, grass duration, grass genera diversity and other abiotic factors such as field aspect, altitude, and meteorological parameters were abiotic factors such as field aspect, altitude, and meteorological parameters were collected at each site. Only grass duration and soil bulk density showed any association with wireworm infestation stauts when considered as single variates. Data from a sub-set of 41 fields were used to develop a series of multi-variate discriminant rules to predit wireworm presence/absece in individual fields. These were vaildated using data from the remaining 21 fields. In general, the rules tended to over-estimate the number of wireworm-infested fields by misclassifying uninfested fields as infestes. Multivariate models to predict wireworm populaiton levels in infested fields were also developed using multiple and generalised linear regression. The predictive accuracy of these was poor. Neither the population prediciton models nor the presence/absence rulses accounted fully for the large inte-field variation in wireworm infestation status.     

DNA Barcoding of Japanese Click Beetles (Coleoptera,Elateridae)

Click beetles (Coleoptera: Elateridae) represent one of the largest groups of beetle insects. Some click beetles in larval form, known as wireworms, are destructive agricultural pests. Morphological identification of click beetles is generally difficult and requires taxonomic expertise. This study reports on the DNA barcoding of Japanese click beetles to enable their rapid and accurate identification. We collected and assembled 762 cytochrome oxidase subunit I barcode sequences from 275 species, which cover approximately 75% of the common species found on the Japanese main island, Honshu. This barcode library also contains 20 out of the 21 potential pest species recorded in Japan. Our analysis shows that most morphologically identified species form distinct phylogenetic clusters separated from each other by large molecular distances. This supports the general usefulness of the DNA barcoding approach for quick and reliable identification of Japanese elaterid species for environmental impact assessment, agricultural pest control, and biodiversity analysis. On the other hand, the taxonomic boundary in dozens of species did not agree with the boundary of barcode index numbers (a criterion for sequence-based species delimitation). These findings urge taxonomic reinvestigation of these mismatched taxa.     

Wireworm (Coleoptera: Elateridae) identity, monitoring and damage in sugarcane

Abstract Wireworms (Coleoptera: Elateridae) damage the eyes and young shoots of germinating cane setts in many growing regions. Insecticides can be applied at planting to avoid damage. However, there are no guidelines for deciding on whether treatment is warranted and a sampling method to detect wireworms before planting has not been developed. Baits of rolled oats were tested as a method for detecting wireworms in preplant fallows. In 1995 at Bundaberg, the reduction in crop establishment when treatment was withheld was positively correlated with the catch of wireworms at baits before planting. However, no similar relationship was seen in 1996 or at Mackay in either 1995 or 1996: severe damage was recorded on one farm at Mackay where no wireworms had been found. A sampling plan was developed to estimate wireworm numbers at baits with a fixed level of precision. Wireworms collected at the baits and in samples from established canefields in Queensland and New South Wales included five named and 21 unnamed species from five genera, the most abundant being Agrypnus , Conoderus and Heteroderes . Possible barriers to the adoption of baiting as a decision-support tool are discussed. Development of a reliable monitoring system would require considerably more research, which could not be justified at present.     

Electrophysiological and behavioral responses of Dendroctonus frontalis (Coleoptera: Curculionidae) to volatiles isolated from conspecifics

Olfactory sensitivity of the southern pine beetle, Dendroctonus frontalis Zimmermann, to compounds isolated from the mid/hindguts of newly emerged conspecific adults was assayed with coupled gas chromatography-electroantennographic detection. All previously reported pheromones for D. frontalis plus eight additional compounds (fenchyl alcohol, myrtenal, cis-verbenol, trans-pinocarveol, acetophenone, trans-myrtanol, cis-myrtanol, and 2-phenylethanol) consistently elicited antennal responses from at least one sex. The eight additional compounds were assayed individually at three release rates (0.4-0.8, 3-9, and 25-100 mg/d) for the ability to alter D. frontalis responses to traps baited with D. frontalis attractant (4 mg/d frontalin and 17 mg/d alpha-pinene). At the high release rate, cis-verbenol enhanced attraction of D. frontalis females, whereas the other seven compounds significantly reduced attraction of one or both sexes. Acetophenone significantly reduced attraction of male D. frontalis at the low release rate, and five compounds (fenchyl alcohol, trans-pinocarveol, acetophenone, cis-myrtanol, and 2-phenylethanol) reduced attraction of one or both sexes at the intermediate rate. Only acetophenone significantly altered the sex ratio of beetles trapped, decreasing the proportion of males. Attraction of predatory checkered beetles (Cleridae) was enhanced by cis-verbenol released at the high rate but was not altered by any compound inhibitory to D. frontalis. Analyses of volatiles from individual D. frontalis indicated that the majority of the eight compounds were produced in greater quantities by newly emerged beetles than ones attacking pine bolts. Five of the compounds were associated predominantly with one sex. Possible ecological roles of these compounds in the biology of D. frontalis are discussed.     

Insecticidal activity of selected monoterpenoids and rosemary oil to Agriotes obscurus (Coleoptera: Elateridae)

Acute toxicities of three naturally occurring monoterpenoid essential oil constituents and the essential oil of rosemary were tested against late instars of Agriotes obscurus (L.) (Coleoptera: Elateridae). Both contact and volatile toxicities of thymol, citronellal, eugenol, and rosemary oil were determined. Also, phytotoxicity of these compounds was evaluated on corn germination and seedling development. Thymol had the greatest contact toxicity (LD50 = 196.0 microg/larva), whereas citronellal and eugenol were less toxic (LD50 = 404.9 and 516.5 microg/larva, respectively). Rosemary oil did not show any significant contact toxicity, even at 1,600 microg/larva. In terms of volatile toxicity, citronellal was the most toxic to wireworm larvae (LC50 = 6.3 microg/cm3) followed by rosemary oil (LC50 = 15.9 microg/cm3), thymol (LC50 = 17.1 microg/cm3), and eugenol (LC50 = 20.9 microg/cm3). Thymol, eugenol, and citronellal significantly inhibited corn seed germination and development, whereas rosemary oil had only minimal phytotoxic effects.     

Differences in Phyllotreta cruciferae and Phyllotreta striolata (Coleoptera: Chrysomelidae) responses to neonicotinoid seed treatments

Insecticidal seed treatments are used commonly throughout the Northern Great Plains of North America to systemically protect seedlings of canola (Brassica napus L. and Brassica rapa L.) from attack by the flea beetles Phyllotreta cruciferae (Goeze) and Phyllotreta striolata (F.) (Coleoptera: Chrysomelidae). Here, we investigated differential responses by the two flea beetle species to the neonicotinoid seed treatments thiamethoxam (Helix and Helix XTra) and clothianidin (Prosper 400) in greenhouse experiments. P. cruciferae experienced higher mortality and fed less when exposed to these compounds than did P. striolata. Beetles of the overwintered and the summer generations responded differently when feeding on seedlings that developed with insecticidal seed treatments, with mortality higher for P. cruciferae in May than in August. When the two flea beetle species were held together at equal densities and allowed to feed on seedlings affected by the seed treatments, mortality of P. cruciferae significantly exceeded that of P. striolata. Differences in efficacies of these compounds for these beetles have ramifications for management strategies in regions where these insects occur sympatrically. Competitive release of P. striolata was previously reported to occur when P. cruciferae was excluded from brassicaceous crops; consequently, the consistent use of these seed treatments over millions of hectares of canola cropland may be a factor that contributes to a shift in prevalence of flea beetle pest species from P. cruciferae toward P. striolata.     

Relative susceptibility of two sweetpotato varieties to storage root damage by sweetpotato flea beetle (Coleoptera: Chrysomelidae) and wireworm (Coleoptera: Elateridae)

The feeding of soil dwelling insects on storage roots is one of the most serious management issues faced by sweetpotato, Ipomoea batatas (L.) Lam. (Convolvulaceae), growers in the southern United States. Field studies were conducted to evaluate the relative susceptibility of two commonly grown sweetpotato varieties to sweetpotato flea beetle, Chaetocnema confinis Crotch (Coleoptera: Chrysomelidae), and wireworms (Coleoptera: Elateridae, various species). The incidence and severity of sweetpotato flea beetle damage was significantly lower in the variety Covington than Beauregard in two small plot replicated studies. Surveys conducted in commercial sweetpotato fields also showed significantly less sweetpotato flea beetle damage in fields planted to Covington compared with those planted to Beauregard. There was no clear evidence of varietal effect on the incidence of wireworm damage in the study. Results indicate that the severity of wireworm damage as measured by the size of feeding scars may be less in Covington than Beauregard.     

New click beetles (Coleoptera: Elateridae) from the cretaceous of Russia and Kazakhstan

A new tribe, two new genera, and seven new species of click beetles are described: Pollostelaterini, trib. nov., Pollostelater baissensis, gen. et sp. nov. from the Lower Cretaceous of Transbaikalia (Baisa locality), five new species in the genus Cryptocoelus Dolin et Nel C. sinitshenkovae, sp. nov. (Romanovka locality), C. shcherbakovi, sp. nov., C. baissensis, sp. nov., C. lukashevichae, sp. nov., C. dolini, sp. nov. (all from Baisa locality), and Turonelater giganteus, gen. et sp. nov. from the Turonian of Southern Kazakhstan (Kzyl-Dzhar locality).     

Emergence trap, a new method to survey Limoniscus violaceus (Coleoptera: Elateridae) from hollow trees

The study of insects inhabiting basal hollow trees presents a methodological challenge inducing the fact that there is very little research done on fauna of this habitat. Many endangered saproxylic species only develop in cavities located at ground level. One of the most emblematic species of the kind is the Violet Click Beetle (Limoniscus violaceus), included in Annex II of the UE “Habitats” Directive. Surveys have been conducted in five Natura 2000 areas using a new method to monitor L. violaceus: the emergence traps. A total of 376 beetle species, including 239 saproxylics, have been identified. Five are considered threatened and are registered on the European Red List of saproxylic beetles and three are included in Annex II of the “Habitats” Directive. Among 191 trees studied, 33 revealed the presence of L. violaceus. Sampling efforts required to detect at least one specimen have been evaluated. Our results show that sampling a minimum of 20 hollow trees in April and May with emergence traps is recommended to obtain a meaningful survey on the presence of the Violet Click Beetle.     

Reassessment of Species Diversity of the Subfamily Denticollinae (Coleoptera: Elateridae) through DNA Barcoding

The subfamily Denticollinae is a taxonomically diverse group in the family Elateridae. Denticollinae includes many morphologically similar species and crop pests, as well as many undescribed species at each local fauna. To construct a rapid and reliable identification system for this subfamily, the effectiveness of molecular species identification was assessed based on 421 cytochrome c oxidase subunit I (COI) sequences of 84 morphologically identified species. Among the 84 morphospecies, molecular species identification of 60 species (71.4%) was consistent with their morphological identifications. Six cryptic and/or pseudocryptic species with large genetic divergence (>5%) were confirmed by their sympatric or allopatric distributions. However, 18 species, including a subspecies, had ambiguous genetic distances and shared overlapping intra- and interspecific genetic distances (range: 2.12%–3.67%) suggesting incomplete lineage sorting, introgression of mitochondrial genome, or affection by endosymbionts, such as Wolbachia infection, between species and simple genetic variation within species. In this study, we propose a conservative threshold of 3.6% for convenient molecular operational taxonomic unit (MOTU) identification in the subfamily Denticollinae based on the results of pairwise genetic distances analyses using neighbor-joining, mothur, Automatic Barcode Gap Discovery analysis, and tree-based species delimitation by Poisson Tree Processes analysis. Using the 3.6% threshold, we identified 87 MOTUs and found 8 MOTUs in the interval between 2.5% to 3.5%. Evaluation of MOTUs identified in this range requires integrative species delimitation, including review of morphological and ecological differences as well as sensitive genetic markers. From this study, we confirmed that COI sequence is useful for reassessing species diversity for polymorphic and polytypic species occurring in sympatric and allopatric distributions, and for a single species having an extensively large habitat.