Distribution of olfactory and some other antennal sensilla in the male click beetle Agriotes obscurus L. (Coleoptera : Elateridae)

The distribution of 5 types of sensilla was statistically analysed on the 4–10th antennal segments of the male click beetle Agriotes obscurus (Coleoptera : Elateridae). The distribution pattern of the trichoid pheromone receptors (T₂ sensilla) and the olfactory basiconic B₁B₂ sensilla on the antennae of male A. obscurus differs significantly from the distribution pattern of the contact chemoreceptors (T₁ sensilla) and probably the non-olfactory B₇ and D sensilla. A significant peculiarity of the distribution of olfactory sensilla is their location on the antennal segments as 2 separate (dorsal and ventral) fields of sensilla. The numbers of T₂ and B₁B₂ sensilla on dorsal fields of sensilla of the 4–10th segments increase towards the apex of the antenna nearly linearly. On ventral fields of sensilla of the 4–10th antennal segments, the number of B₁B₂ sensilla is nearly uniform; the number of T₂ sensilla in the proximal part of the antenna increases towards the apex, but on distal segments of the antenna their number stabilizes. It is characteristic of both the T₂ and to B₁B₂ sensilla that their numbers are slightly greater on anterior than posterior sides of dorsal sensillar fields, and also greater on posterior than anterior sides of ventral sensillar fields of all antennal segments investigated. We assume that the number of olfactory sensilla on the antennae of male beetles coincides with the distribution of strength of olfactory signal on the antennae of beetles orientating in an odour plume. The distribution patterns of T₂ and B₁B₂ sensilla of the male A. obscurus can be related to some behavioural peculiarities of olfactory orientation (walking or flying and vibrating of the antennae).     

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).     

Measuring trap efficiency for bark beetles (Col., Scolytidae)

Abstract:  The relative efficiency of cylindrical, linear and cross-barrier traps for trapping bark beetles was investigated based on a theoretical model. Using this model, the effective trap interception area of each trap type was calculated and trap efficiency was defined as the ratio of the effective interception area to the trap surface area. The relative efficiencies of the three trap types were calculated as the ratios of their respective effective interception areas. Based on this approach, assuming random directional movement of dispersing beetles, the order of efficiency of the three trap types, from highest to lowest, was linear, cross-barrier and cylindrical. The expected ratios of trap catches based on the relative efficiencies of the three trap types were fitted to data from trapping experiments with the mountain pine beetle ( Dendroctonus ponderosae Hopkins). In general, there was large variation in trap catches among traps of the same type but the ratios of mean catches per trap conformed to the expected ratios. The results indicate that the model of trap efficiency could be used for designing efficient traps. The methods presented are amenable for assessing the efficiency of other trap designs.     

Large scale Agriotes spp. click beetle (Coleoptera: Elateridae) invasion of crop land from field margin reservoirs

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Determination of Agriotes obscurus (Coleoptera: Elateridae) sex pheromone attraction range using target male behavioural responses

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Notes on the fauna and taxonomy of the click beetles (Coleoptera,Elateridae) of Russia and neighboring countries

New data on the distribution and taxonomy of some species of click-beetles in Russia and adjacent countries are given. Several species are recorded for the first time for the following territories: Brachygonus bouyoni (Chass.), B. dubius (Plat. et Cate) and Zorochros lewisi (Schw.), for Russia; Sericus sulcipennis (Baudi), for Ukraine; Berninelsonius hyperboreus (Gyll.), Cidnopus parallelus (Motsch.), and Limonius poneli Les. et Mertl., for Kazakhstan. New interesting findings of Sericus sulcipennis and Selatosomus songoricus (Kr.) are reported. Comments on some erroneous faunistic records of several elaterids, including some species from Middle Asia, are made. The following new synonymy is established: Haterumelater fulvago (Marseul, {dy1868}) = Elater tauricola Gurjeva, 1957, syn. n. Notes on the variability of Selatosomus latus (F.) are given, and its conspecificity with S. corpulentus (Cand.) is confirmed. The external morphology and genitalia of the little known Selatosomus nanus Gur. are studied, and the systematic position of this species is discussed.     

Phylogenetic relationships of click beetles (Coleoptera: Elateridae) inferred from 28S ribosomal DNA: insights into the evolution of bioluminescence in Elateridae

Although the taxonomy of click beetles (family Elateridae) has been studied extensively, inconsistencies remain. We examine here the relationships between species of Elateridae based on partial sequences of nuclear 28S ribosomal DNA. Specimens were collected primarily from Japan, while luminous click beetles were also sampled from Central and South America to investigate the origins of bioluminescence in Elateridae. Neighbor-joining, maximum-parsimony, and maximum-likelihood analyses produced a consistent basal topology with high statistical support that is partially congruent with the results of previous investigations based on the morphological characteristics of larvae and adults. The most parsimonious reconstruction of the "luminous" and "nonluminous" states, based on the present molecular phylogeny, indicates that the ancestral state of Elateridae was nonluminous. This suggests that the bioluminescence in click beetle evolved independent of that of other luminous beetles, such as Lampyridae, despite their common mechanisms of bioluminescence.     

Vision in click beetles (Coleoptera: Elateridae): pigments and spectral correspondence between visual sensitivity and species bioluminescence emission

Among lampyrids, intraspecific sexual communication is facilitated by spectral correspondence between visual sensitivity and bioluminescence emission from the single lantern in the tail. Could a similar strategy be utilized by the elaterids (click beetles), which have one ventral abdominal and two dorsal prothoracic lanterns? Spectral sensitivity [S(λ)] and bioluminescence were investigated in four Brazilian click beetle species Fulgeochlizus bruchii, Pyrearinus termitilluminans, Pyrophorus punctatissimus and P. divergens, representing three genera. In addition, in situ microspectrophotometric absorption spectra were obtained for visual and screening pigments in P. punctatissimus and P. divergens species. In all species, the electroretinographic S(λ) functions showed broad peaks in the green with a shoulder in the near-ultraviolet, suggesting the presence of short- and long-wavelength receptors in the compound eyes. The long-wavelength receptor in Pyrophorus species is mediated by a P540 rhodopsin in conjunction with a species-specific screening pigment. A correspondence was found between green to yellow bioluminescence emissions and its broad S(λ) maximum in each of the four species. It is hypothesized that in elaterids, bioluminescence of the abdominal lantern is an optical signal for intraspecifc sexual communication, while the signals from the prothoracic lanterns serve to warn predators and may also provide illumination in flight.     

Spinosad interacts synergistically with the insect pathogen Metarhizium anisopliae against the exotic wireworms Agriotes lineatus and Agriotes obscurus (Coleoptera: Elateridae)

We determined that spinosad interacts synergistically with the biocontrol agent Metarhizium anisopliae (Metch) Sorokin to increase the mortality of two wild-collected wireworm species, Agriotes lineatus (L.), and Agriotes obscurus (L.). Bioassays were performed using a M. anisopliae isolate originally acquired from a local wireworm cadaver. M. anisopliae was applied as a soil drench at 3.3 x 10(2) and 10(4) conidia per gram sand, respectively. Soil drenches also were prepared using a commercial formulation of the actinomycete toxins spinosyn-A and spinosyn-D (common name spinosad) at sublethal doses of 1.5, 3, and 6 ppm active ingredient per gram sand. Combined treatments of spinosad and M. anisopliae were synergistic in causing mortality for all spinosad concentrations. Wireworm feeding activity was reduced after exposure to both spinosad and M. anisopliae and was found to be concentration dependent. The high mortality and reduced rate of wireworm feeding suggest that spinosad and M. anisopliae treatment combinations should be tested in the field.     

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.     

The jump of the click beetle (Coleoptera, Elateridae)—a preliminary study

A preliminary account is given of the jump of the click beetle, Athous haemorrhoidalis (F.). The jump is normally made from an inverted position. It involves a jack-knifing movement whereby a prosternal peg is slid very rapidly down a smooth track into a mesosternal pit. The muscles which produce this movement are allowed to build up tension by a friction hold on the dorsal side of the peg. The anatomy of this jumping mechanism is briefly described. Ciné recording showed that the jump was usually nearly vertical and could exceed 0.3m in height; the beetle normally rotated several times head over tail during a jump. The jump was produced by a very rapid upwards movement of the beetle's centre of gravity during the jack-knifing action. In a typical jump, a 4 × 10⁻⁵ kg beetle could be subjected to an upwards acceleration of 3800 m/s⁻² (380 g). The minimum work done and the power output of the muscles causing jumping have been calculated. A simple mechanical model has been constructed to simulate a jump, and several possible ways in which the jumping mechanism could operate have been discussed.     

Aggregation and mortality of Agriotes obscurus (Coleoptera: Elateridae) at insecticide-treated trap crops of wheat

Agriotes obscurus (L.) wireworms assembled in increasing numbers at rows of treated (Agrox DL Plus seed treatment) and untreated wheat, Triticum aestivum L., planted at increasing densities (0, 0.15, 0.30, and 0.60 seeds/cm). In treated wheat plots at all planting densities, no wireworm damage to seedlings was apparent, and total wireworms taken in core samples in wheat rows increased according to the asymptotic equation y = B0(1 -e(-Blx)), where B0 is the asymptote, B1 is the slope of the initial rise, and x is the seeding density. The number of dead wireworms in treated plots increased linearly and intercepted the asymptotic models (theoretical point at which 100% mortality of assembled population occurs) at 0.95 seeds/cm on 11 June and 1.14 seeds/cm on 18 June 1996. Untreated wheat at all densities planted had severe wireworm damage and significantly reduced stand. Populations that had assembled at the surviving untreated wheat were fewer than in the treated wheat plots, and although increasing with seeding density, did not follow the asymptotic model. The data suggest that A. obscurus populations can be assembled and killed in fallowed fields in large numbers at treated trap crops of wheat over a 19-d period when planted in rows spaced 1 m apart at a linear seeding density of 1.5 seeds/cm.     

Laboratory and field evaluation of entomopathogenic nematodes for control of Agriotes obscurus (L.) (Coleoptera: Elateridae)

The susceptibility of the dusky wireworm, Agriotes obscurus (L.) (Coleoptera: Elateridae), to different species and strains of entomopathogenic nematodes was tested in a virulence assay in the laboratory. Larvae were exposed to different nematode doses of 50 and 100 IJs/cm². At a dose of 50 IJs/cm², only a commercial strain Heterorhabditis bacteriophora Poinar and the native strain Steinernema carpocapsae (Weiser) B14 caused increased mortality compared with the control (11.1% and 13.3% mortality, respectively). At the higher dose tested, all strains (except Steinernema sp. D122) were virulent to A. obscurus larvae. Steinernema carpocapsae B14 caused higher mortality of wireworm (75.6%) and was used for the assay conducted in cages, with a dose of 100 IJs/cm², in field conditions. The results showed that S. carpocapsae B14 controlled 48.3% of A. obscurus larvae, demonstrating that some entomopathogenic nematodes have the potential to control larvae of A. obscurus. However, further work is needed to improve their efficacy.     

Numerical response of ladybird beetles (Col., Coccinellidae) to aphid prey (Hom., Aphididae) in a field bean in north-east India

Two predaceous species of Coccinellidae, Menochilus sexmaculatus and Coccinella transversalis , occurred abundantly in bean crops infested with the aphid, Aphis craccivora Koch in north-east India. The number of eggs and adults of the two coccinellids increased in response to the increase in the population of aphid prey. Reproductive numerical responses were found to be synchronous to prey density whereas aggregative numerical responses appeared asynchronous in the later part of the aphid cycle on beans. Menochilus sexmaculatus oviposited smaller clusters of eggs at lower density of aphids than C. transversalis which laid larger clusters and showed greater numerical response at higher densities of aphids. Within a species cluster the size of the eggs seems to be directly related to aphid density. The two coccinellid species of this study seem to be efficient predators of A. craccivora in terms of their reproductive and aggregative numerical responses.     

Studies on predation of Prostephanus truncatus (Horn) (Col., Bostrichidae) and Sitophilus zeamais Mots. (Col., Curculionidae) at different densities on maize by Teretriosoma nigrescens Lewis (Col., Histeridae)

Laboratory experiments using whole cobs were conducted to examine the effect of varying densities of the larger grain borer, Prostephanus truncatus and the maize weevil, Sitophilus zeamais on rate of population increase by the histerid beetle, Teretriosoma nigrescens , a predator primarily of P. truncatus . Densities of all species of insects were determined at the end of the experiment, and an electrophoretic analysis of gut content was conducted on larval and adult T. nigrescens sampled during the experiments. Results indicated that T. nigrescens has a strong preference for P. truncatus and densities of T. nigrescens were associated only with densities of P. truncatus . The maize weevil played little role as an alternative prey or in interfering with T. nigrescens reproduction.     

Host specificity of ambrosia and bark beetles (Col., Curculionidae: Scolytinae and Platypodinae) in a New Guinea rainforest

Abstract.  1. Bark and ambrosia beetles are crucial for woody biomass decomposition in tropical forests worldwide. Despite that, quantitative data on their host specificity are scarce.
2. Bark and ambrosia beetles (Scolytinae and Platypodinae) were reared from 13 species of tropical trees representing 11 families from all major lineages of dicotyledonous plants. Standardised samples of beetle-infested twigs, branches, trunks, and roots were taken from three individuals of each tree species growing in a lowland tropical rainforest in Papua New Guinea.
3. A total of 81 742 beetles from 74 species were reared, 67 of them identified. Local species richness of bark and ambrosia beetles was estimated at 80–92 species.
4. Ambrosia beetles were broad generalists as 95% of species did not show any preference for a particular host species or clade. Similarity of ambrosia beetle communities from different tree species was not correlated with phylogenetic distances between tree species. Similarity of ambrosia beetle communities from individual conspecific trees was not higher than that from heterospecific trees and different parts of the trees hosted similar ambrosia beetle communities, as only a few species preferred particular tree parts.
5. In contrast, phloeophagous bark beetles showed strict specificity to host plant genus or family. However, this guild was poor in species (12 species) and restricted to only three plant families (Moraceae, Myristicaceae, Sapindaceae).
6. Local diversity of both bark and ambrosia beetles is not driven by the local diversity of trees in tropical forests, since ambrosia beetles display no host specificity and bark beetles are species poor and restricted to a few plant families.     

Linking climate change and insect pest distribution: an example using Agriotes ustulatus Shall. (Coleoptera: Elateridae)

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