Comparative Antennal Morphology of Agriotes (Coleoptera: Elateridae), with Special Reference to the Typology and Possible Functions of Sensilla

Species of the click-beetle genus Agriotes Eschscholtz are economically important crop pests distributed mainly in the Northern Hemisphere. They can inflict considerable damage on various field crops. Therefore, the detection, monitoring, and control of Agriotes include the adult trapping using species-specific sex pheromones, which is a critical component of pest research. To obtain a better understanding of the detailed antennal morphology as background information for subsequent chemical ecology research, we conducted a scanning electron microscopy study of the antennal sensilla of both sexes in 10 European Agriotes species. We identified 16 different sensilla in Agriotes, belonging to six main types: sensilla chaetica (subtypes C1 and C2), sensilla trichodea, sensilla basiconica (subtypes B1–B9), dome-shaped sensilla (subtypes D1 and D2), sensilla campaniformia, and Böhm sensilla. We discuss their possible functions and compare the sensilla of Agriotes with those of other Elateridae in order to consolidate the sensillum nomenclature in this family. Additionally, our study reveals the remarkable interspecific variability in sensillar equipment of Agriotes and identifies several characters of potential importance for future use in systematic studies. The present study provides a strong preliminary framework for subsequent research on the antennal morphology of this crop pest on a wider scale.

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title: Agricultural Insect Pests of Temperate Regions and their Control
abstract: This handbook is a companion to Agricultural Insect Pests of the Tropics and their Control (2nd Edition 1983) and, like the earlier book, it is designed as a source of reference about most of the major insect and mite pests of agricultural crops. These two volumes by the same author now present a world-wide coverage of the economically important insect pests of tropical and temperate agriculture. Students taking courses in entomology, agriculture, crop pest biology and crop protection, and professional workers concerned with identification and control of insect pests, will find this comprehensive account an indispensable handbook and source of reference.

title: The biology and management of wireworms (Agriotes spp.) on potato with particular reference to the U.K.
abstract: 1 This paper reviews and interprets relevant work on the biology and management of wireworms (Agriotes spp.) within the context of potato production in Europe, with particular reference to the U.K. Although the review concentrates on Agriotes spp., the extensive world literature on other Elateridae of economic importance is also drawn upon.

title: Control methods and monitoring of Agriotes wireworms (Coleoptera: Elateridae)
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title: Quality deficiencies on potato (Solanum tuberosum L.) tubers caused by Rhizoctonia solani, wireworms (Agriotes ssp.) and slugs (Deroceras reticulatum, Arion hortensis) in different farming systems
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title: A New Species of the Agriotes nuceus Species Group from Turkey
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title: The efficacy of the new Agriotes sex pheromone traps in detecting wireworm population levels in different european countries
abstract: New Agriotes sex pheromone traps were tested in different European countries enabling the suitability of the traps in monitoring different populations and the relationship between pheromone trap catches and wireworm population levels to be studied under a range of climatic and agronomic conditions. Trials were done in the United Kingdom, Eastern Croatia, Central Croatia, central Romania, Central Eastern Romania, Germany, Bulgaria from 1999 to 2001. The areas of the regions where the experimentation was done have very variable climati and agronomic characteristics ( latitude ranged from 42* to 56*). All trials were done using a common protocol. In the first 2 years YALTOR and VARb traps were used while in 2001 a trap design suitable for both flying and crawling species (YALTORfunnel) was used. Individual traps were baited with the lures for one of the following species: A. lineatus L., A. oscurus, L., A. sputator, L., A.sordidus Illiger, A. rufipalpis, Brulle, A.brevis Candeze, A. litigiosus Rossi, A. ustulatus Schaller. Larval population was estimated by using bait traps and soil sampling. In all regions conducting studies the pheromone trap were confirmed to e a sensitive tool for detecting the key wireworm species present. Al all sites it was possible to detect the dominant species. Furthermore the traps appeard to be selective enough to distinguish A. sputator and A. brevis despite these two species being sistematically very close. Males of minor species (also not Agriotes) were found in some traps (for example Cyndopus pilosus Leske in Bulgaria). The response of the different species to the different monitoring tools was very variable. Generally sex pheromone traps proved to be much more sensitive tool than soil sampling and bait traps for larvae. For all species traps were able to detect wireworm populations below those that can be reliably detected using soil sampling and bait trapping. In addition pheromone traps proved to be effective in detecting the regional variations of swarming patterns of the same species.

title: Ultrastructure of invertebrate chemo-, thermo-, and hygroreceptors and its functional significance.
abstract: Publisher Summary Chemo-, thermo-, and hygroreceptors are primary sensory cells, which bear one or several modified cilia whose membranes are specialized to take part in the transduction process. These membranes must be exposed to the stimuli but also be protected against desiccation, mechanical, and other injury. Hence, a variety of structural specializations is found that serves these functions. In insects, chemo-, thermo-, and hygroreceptive sensory cells are located exclusively in sensilla, which are organelles built up by a definite number of characteristic cells. During development, the innermost enveloping cell produces a cuticular sheath (scolopale), which envelops the dendritic processes for varying distances along their course through the receptor lymph cavity. This sheath producing cell is surrounded by the trichogen cell, which is itself surrounded by the trichogen cell. These cells build up shaft and socket, respectively, of the cuticular outer structures during development. The perikarya of all cells of the sensillum are enclosed within the epidermis.

title: Ultrastructural characterization of antennal sensilla and immunocytochemical localization of a chemosensory protein in Carausius morosus Brünner (Phasmida: Phasmatidae).
abstract: The aim of this work was to investigate the olfactory system of the walking stick insect, Carausius morosus. Morphological, ultrastructural and immunocytochemical studies of adult female antennae were conducted by scanning and transmission electron microscopy. Extensive cross-section series were made through the last antennal segment to define the cuticular apparatus, wall pore distribution and the number of innervating receptor neurons of each sensillum type. Single-walled wall pore sensilla occur in three subtypes: (i) with 27 or 28 branched receptor neurons, (ii) with two branched neurons and (iii) with one or two unbranched neurons, respectively. Double-walled wall pore sensilla were found in two subtypes with spoke channels, one with four unbranched neurons, the other with two unbranched neurons. One terminal pore sensillum was found, showing two cavities within the hair and being innervated by six sensory cells. Immunocytochemical experiments were performed to show the localization of a 19 kDa soluble protein found in the chemosensory organs of C. morosus. This protein shows an amino acid sequence homologous to the family of chemosensory proteins (CSP). The polyclonal antibody raised against the purified protein (CSP-cmA) showed, for the first time in CSPs, a strong labeling in olfactory sensilla, specifically in the sensillum lymph surrounding the dendritic branches of SW-WP sensilla and in the uninnervated lumen between the two concentric walls of DW-WP type 1 sensilla.

title: Bursty spike trains of antennal thermo- and bimodal hygro-thermoreceptor neurons encode noxious heat in elaterid beetles.
abstract: The main purpose of this study was to explain the internal fine structure of potential antennal thermo- and hygroreceptive sensilla, their innervation specifics, and responses of the sensory neurons to thermal and humidity stimuli in an elaterid beetle using focused ion beam scanning electron microscopy and electrophysiology, respectively. Several essential, high temperature induced turning points in the locomotion were determined using automated video tracking. Our results showed that the sensilla under study, morphologically, are identical to the dome-shaped sensilla (DSS) of carabids. A cold-hot neuron and two bimodal hygro-thermoreceptor neurons, the moist-hot and dry-hot neuron, innervate them. Above 25-30 °C, all the three neurons, at different threshold temperatures, switch from regular spiking to temperature dependent spike bursting. The percentage of bursty DSS neurons on the antenna increases with temperature increase suggesting that this parameter of the neurons may encode noxious heat in a graded manner. Thus, we show that besides carabid beetles, elaterids are another large group of insects with this ability. The threshold temperature of the beetles for onset of elevated locomotor activity (OELA) was lower by 11.9 °C compared to that of critical thermal maximum (39.4 °C). Total paralysis occurred at 41.8 °C. The threshold temperatures for spike bursting of the sensory neurons in DSS and OELA of the beetles coincide suggesting that probably the spike bursts are responsible for encoding noxious heat when confronted. In behavioural thermoregulation, spike bursting DSS neurons serve as a fast and firm three-fold early warning system for the beetles to avoid overheating and death.

title: Carbon‐dioxide sensing structures in terrestrial arthropods
abstract: Sensory structures that detect atmospheric carbon dioxide have been identified and described to the subcellular level in adults of Lepidoptera, Diptera, Hymenoptera, Isoptera, Chilopoda, and Ixodidae, as well as in lepidopteran larvae. The structures are usually composed of clusters of wall‐pore type sensilla that may form distinct sensory organs, often recessed in pits or capsules. In insects, they are located on either the palps or the antennae, in chilopods on the head capsule, and in ixodids on the forelegs. In the two cases where the central projections have been examined (Lepidoptera and mosquitoes), the clustering is preserved to the level of second order neurons, which are located in the deutocerebrum. Individual sensilla usually contain a single receptor neuron that is sensitive to CO2; it may be accompanied by other neurons that respond to other olfactory qualities. The distal dendritic processes of CO2‐sensitive neurons invariably show an increased surface area, dividing into many cylindrical branches or into lamellar structures. Lamellar membranes are often closely linked to arrays of microtubules. Fine pore canal tubules are usually associated with the cuticular pores.  1999.

title: External morphology of antennal sensilla of four species of adult flea beetles (Coleoptera : chrysomelidae : alticinae)
abstract: External morphology of antennal sensilla of both sexes of Phyllotetra cruciferae (Goeze) and Psylloides punctulata Melsh, both of which feed on the mustard family Cruciferae, and Epitrix cucumeris (Harris) and Psylloides affinis (Paykell), both of which feed on the nightshade family Solanaceae, was studied using scanning electron microscopy. All belong to Alticinae (Coleoptera : Chrysomelidae). The number and distribution of antennal sensilla were also determined. Eight types of sensilla could be distinguished on the flagella of the species examined: sensilla chaetica; sensilla trichodea I and II; long sensilla basiconica I and II; and short sensilla basiconica I, II and III. The sensilla chaetica are probable tactile mechanosensilla, whereas both types of sensilla trichodea and long sensilla basiconica likely function in olfaction. Suggested functions for the short sensilla basiconica I, II and III include hygro-/thermoreception and chemoreception. The lack of sexual dimorphism in antennal structure and in types as well as number of sensilla, indicates that the sensilla probably have similar functions in both sexes. Probably most of the antennal olfactory sensilla are involved in host location and recognition. Any correlation between number of a particular type of sensillum or total number of all types and general host preference is not apparent.

title: Evaluation of Pheromones and a New Trap for Monitoring Agriotes lineatus and Agriotes obscurus in the Fraser Valley of British Columbia
abstract: A prototype ground-based pheromone trap design, baited with various pheromone lures, was field tested for effectiveness in trapping male Agriotes obscurus and Agriotes lineatus click beetles in British Columbia. Pheromone dispensers containing geranyl octanoate and geranyl hexanoate in a 1:1 ratio caught the greatest numbers of A. obscurus, whereas those containing geranyl octanoate and geranyl butanoate in a 9 or 10:1 ratio caught high numbers of A. lineatus. Some differences in A. obscurus attraction to traps were observed between dispensers according to the manufacturer and the number of dispensers deployed in traps. The trap design and optimal pheromone dispensers tested would be suitable for monitoring or surveying A. obscurus and A. lineatus populations in North America.

title: Distribution of olfactory and some other antennal sensilla in the male click beetle Agriotes obscurus L. (Coleoptera : Elateridae)
abstract: 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 (T 2 sensilla) and the olfactory basiconic B 1 B 2 sensilla on the antennae of male A. obscurus differs significantly from the distribution pattern of the contact chemoreceptors (T 1 sensilla) and probably the non-olfactory B 7 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 T 2 and B 1 B 2 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 B 1 B 2 sensilla is nearly uniform; the number of T 2 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 T 2 and to B 1 B 2 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 T 2 and B 1 B 2 sensilla of the male A. obscurus can be related to some behavioural peculiarities of olfactory orientation (walking or flying and vibrating of the antennae).

title: Antennal sensilla of the click beetle, limonius aeruginosus (OLIVIER) (COLEOPTERA: ELATERIDAE)
abstract: Antennal sensilla typology, number and distribution of the click beetle Limonius aeruginosus (Olivier) (Coleoptera: Elateridae) were studied using scanning electron microscopy. The serrate antennae of both sexes of L. aeruginosus consist of the scape, pedicel and of the flagellum which is composed of 9 flagellomeres. In both sexes, 5 types of sensilla basiconica, 1 type of sensilla trichodea, 1 type of sensilla chaetica, 1 type of sensilla campaniformia and Bohm sensilla were distinguished. No remarkable sexual differences in the types, numbers and distribution of sensilla were found on the antennae, except for the sensilla basiconica type II. The average number of sensilla basiconica type II on the antennae of the male beetle surpassed that on the antennae of the female beetle (3562 and 108 pegs, respectively). It is suggested that this type of sensilla on the male beetles antennae is responsible for the reception of the sex pheromone produced by the female beetle.

title: Antennal sensilla of the click beetle, Melanotus villosus (Geoffroy) (Coleoptera: Elateridae)
abstract: The typology, number and placement of antennal sensilla of the click beetle Melanotus villosus (Geoffroy) (Coleoptera: Elateridae) were studied using scanning electron microscopy. On both the males and females the antennae are made up of the scape, pedicel and nine flagellomeres. Two types of basiconic sensilla, three types of trichoid sensilla, one type of styloconic sensilla, one type of chetoid sensilla, dome-shaped sensilla, grooved pegs, and Bohm sensilla all appear on the antennae of the beetles of both sexes, with the exception of trichoid sensilla type II, whose large number (average of 1635 hairs per antenna) was found only in male beetles. Sensilla trichodea type II evidently respond to the sex pheromone produced by the female beetle. Unlike the other two click beetles, studied up till now, Agriotes obscurus and Limonius aeruginosus, the trichoid and basiconic sensilla of M. villosus, whose proven or assumed function is olfactory, are located predominantly on the flagellomeres ventral extensions. It is assumed that the placement of the olfactory sensilla, mainly on the ventral side of M. villosuss antennae, and their more or less even distribution on the flagellomeres, can be seen as morphological adaptation of this species of insect, whose specific behavioural reaction of olfactory searching is flying, both before and after contact with an odour plume.

title: Scanning electron microscopy analysis of the antennal sensilla in the rare saproxylic beetle Elater ferrugineus (Coleoptera: Elateridae)
abstract: This work provides the first morphological analysis (both at gross and fine level) of the antennal structures in the genus Elater (Coleoptera, Elateridae). The typology, number and distribution patterns of the antennal sensilla in the rare saproxylic Elater ferrugineus (both male and female) were studied using scanning electron microscopy (SEM). The serrate antennae of E. ferrugineus consisted of a scape, a pedicel, and nine flattened flagellomeres. Overall, 10 types of sensilla were identified according to their morphological features: one type of sensilla chaetica (Ch), one type of Böhm sensilla (Bo), three types of sensilla trichodea (Tr.1–3), two types of sensilla basiconica (Ba.1–2), one type of sensilla styloconica (St), one type of grooved peg sensilla (Gp) and one type of sensilla campaniformia (Ca). A marked sexual dimorphism was found at both gross and fine scale. The male antenna was bigger (8.6 mm) than the female one (7.0 mm) and carried one type of sensilla trichodea (Tr.2) absent in female antennae possibly responsible for reception of the female-emitted sex pheromone. The female antenna carried a higher number of sensilla (~ 9800) than the male one did (~7,000), with more abundant sensilla chaetica (Ch) and basiconica (Ba.1 and Ba.2).

title: Comparative antennal morphology of male Drilini with special reference to the sensilla (Coleoptera: Elateridae: Agrypninae)
abstract: The click-beetle tribe Drilini (Coleoptera: Elateridae: Agrypninae) contains species with soft-bodied, fully winged males and larviform apterous females. Currently, three genera comprising approximately 120 species have been classified in Drilini – Drilus Olivier, Malacogaster Bassi, and Selasia Laporte. The relationships within the group remain unclear due to the confused taxonomy and variable traditionally used morphological diagnostic characters. To obtain a better understanding of the detailed antennal morphology and its potential taxonomic use within Drilini, we conducted a scanning electron microscopy study of the antennal sensilla of the males of nine species representing all known genera. Additionally, we examined the specimens from three geographically distinct populations of the widely distributed D. flavescens (Geoffroy) to infer the intraspecific variability in their antennal morphology. We observed 20 different sensilla structures in Drilini, belonging to four main types: sensilla chaetica (subtypes C1–C2), sensilla basiconica (B1–B16), Bohm sensilla, and sensilla campaniformia. We found that some sensilla basiconica are useful for the identification of Drilini at the generic and species levels. Malacogaster and Selasia bear several genus-specific sensilla; however, we have not found any sensillum typical for only Drilus. What is more, even the distant geographic populations of D. flavescens differ in the number of sensilla basiconica subtypes. Our results strongly support the close relationship of Drilus and Malacogaster due to their similar antennal sensillar equipment. This study provides the first step towards furthering research on antennal morphology within Drilini and its significance for the taxonomy of the group.

title: Observation of antennal sensilla in Xylotrechus grayii (Coleoptera: Cerambycidae) with scanning electron microscopy
abstract: The longicorn beetle Xylotrechus grayii (White, 1855) has been spreading rapidly in China, causing mass mortality of honeysuckle which is economically and medicinally important. In order to elucidate the mechanisms of mate and host location and to advance efficient control methods, antennal sensilla features were investigated in both sexes of X. grayii using scanning electron microscopy (SEM). The filiform antennae of both sexes consist of scape, pedicel, and nine flagellomeres (f1–9). Five types of sensilla were observed: sensilla chaetica (5 subtypes, SC1–5), sensilla basiconica (4 subtypes, SB1–4), Böhm bristles (Bm), grooved peg sensilla (Gp), and sensilla campaniformia (Ca). SC were most common on the antennae, followed by SB and Bm. No significant sexual differences in the type, amounts, and distribution of antennal sensilla were found except for the distribution of SB clusters and Ca. SB clusters and Ca occurred on f1–8 of male antennae but were absent on those segments in females, suggesting a potential function as receptors for female sex pheromones. The putative functions of other sensilla are discussed based on their characteristics in related species. This study provides an important foundation for further research on sensory mechanisms and control measures of X. grayii.  2014.

title: Sensilla on the antennal flagellum of the sawyer beetles Monochamus notatus (Drury) and Monochamus scutellatus (Say) (Coleoptera: Cerambycidae)
abstract: The antennae of the sawyer beetles Monochamus notatus and M. scutellatus were examined with the light and scanning electron microscopes to determine the types, number, distribution and innervation of the sense organs. Nine types of sensilla are described. Both short, thin‐walled pegs (sensilla basiconica) and reversely curved thick‐walled hairs (sensilla trichodea) are chemoreceptors. There are three types of long, thick‐walled hairs (sensilla chaetica) which may be mechanoreceptors. One of these is modified in males to form unique snail‐shaped pegs. A few dome‐shaped organs, probably campaniform sensilla, were found.

title: Antennal sensilla of the pecan weevil, Curculio caryae (Horn) (Coleoptera:Curculionidae)
abstract: Scanning electron microscopy revealed 2 types of sensilla trichodea, 4 types of sensilla basiconica, and one type of sensilla styloconica on the antennal club of the pecan weevil, Curculio caryae. All receptor types are found on both male and female weevils and their distribution is similar. The total number of sensilla on the antennal club of the male is estimated to be 1467 and on the female 1491. Significant differences in numbers of basiconica type I exist for dorsal and ventral surfaces on the male but not on the female. A significant difference in number exists between the sexes for trichodea type I and for dorsal/ventral surfaces on the female. Significant differences exist in length between the sexes for trichodea type I on segments 2 and 3 and trichodea type II on all 3 segments. The porous surface present on basiconica type I sensilla indicates a possible olfactory function.

title: Antennal sensilla of the ground beetle Bembidion lampros Hbst (Coleoptera, Carabidae).
abstract: Merivee, E., Ploomi, A., Rahi, M., Luik, A. and Sammelselg, V. 2000. Antennal sensilla of the ground beetle Bembidion lampros Hbst (Coleoptera, Carabidae). — Acta Zoologica (Stockholm) 81 : 339‐350 Antennal sensilla typology, number and distribution pattern were studied in the ground beetle Bembidion lampros Hbst (Coleoptera, Carabidae) using scanning electron microscopy. The 1.6‐1.8 mm long filiform antennae of both sexes consist of the scape, pedicel and of the flagellum composed of nine flagellomeres. In both sexes, three types of sensilla chaetica, two types of sensilla trichodea, five types of sensilla basiconica, one type of sensilla coeloconica, one type of sensilla campaniformia and Bohm sensilla were distinguished. The possible function of the sensilla was discussed and three types of sensilla were considered as olfactory, sensilla trichodea type 2 and sensilla basiconica types 1 and 2. Olfactory sensilla occupy dorsal and/or ventral areas of the flagellomeres and occur sparsely (sensilla basiconica type 1) or not at all (sensilla basiconica type 2 and sensilla trichodea type 2) outside these areas. No remarkable sexual differences in the types, numbers and distribution of antennal sensilla were found.

title: Antennal sensilla of the ground beetle Platynus dorsalis (Pontoppidan, 1763) (Coleoptera, carabidae)
abstract: The typology, number, and distribution pattern of antennal sensilla of the ground beetle Platynus dorsalis (Pontoppidan) (Coleoptera, Carabidae) were studied using scanning electron microscopy. The 4.3–4.6‐mm‐long filiform antennae of the beetles consist of the scape, pedicel, and nine flagellomeres. In both sexes, four subtypes of sensilla chaetica, five subtypes of sensilla basiconica, sensilla trichodea, two subtypes of sensilla campaniformia, sensilla auricillica, and sensilla coeloconica were distinguished. The possible function of the sensilla was discussed and three types of sensilla were considered as olfactory, sensilla trichodea and sensilla basiconica types 1 and 2. Olfactory sensilla form two separate, dorsal and ventral, fields of sensilla on the flagellomeres, which seems to be common in ground beetles. The total numbers of olfactory trichoid (approximately 1,000 hairs) and basiconic sensilla type 1 (1,700–1,800 pegs) on the antennae of P. dorsalis are 5–7 times higher than on the antennae of the ground beetle Bembidion lampros, suggesting that nocturnally active P. dorsalis is much more sensitive to odours perceived by these sensilla than B. lampros with diurnal activity and hunting predominantly by sight. No remarkable sexual differences in the types, numbers, and distribution of antennal sensilla were found in P. dorsalis.  2001.

title: Identification and electroantennographic activity of sex-specific geranyl esters in an abdominal gland of femaleAgriotes obscurus (L.) andA. lineatus (L.) (Coleoptera, Elateridae)
abstract: Both geranyl hexanoate and geranyl octanoate were identified by GC/MS as the major volatiles in a hitherto uncharacterized abdominal gland in females inAgriotes obscurus. Only geranyl octanoate was found inA. lineatus. In EAG tests performed onA. obscurus males, geranyl butanoate and geranyl hexanoate elicited the strongest antennal responses.

title: Identification of female‐produced sex pheromones and their geographical differences in pheromone gland extract composition from click beetles (Col., Elateridae)
abstract: Female sex pheromone of click beetles represent multicomponent systems. From 1980 to 1993 pheromones of Agriotes, Sinaptus and Melanotus genera were examined. The esters of geraniol, 8‐hydroxygeraniol, 8‐hydroxynerol (E,E)‐farnesol and all‐trans geranylgeraniol were identified as the components of the sex pheromones. In the pheromone glands some species of click beetles contain up to 24 substances. This study confirms the existence of pheromone dialects in Agriotes sputator L. and Agriotes obscurus L. populations.

title: Identification of Sex Pheromone Composition of Click Beetle Agriotes brevis Candeze
abstract: Geranyl butyrate (GB) and (E,E)-farnesyl butyrate (FB) were identified in the pheromone gland extract of females of the click beetle, Agriotes brevis (Candeze) (Coleoptera: Elateridae) as the major sex pheromone components. Polyethylene vial dispensers containing 20–200 mg of a 1:1 mixture caught high numbers of beetles. Captures did not decrease even after 73 days of field exposure of dispensers. At sites where both Agriotes sputator L. and A. brevis were present, the above baits were selectively catching only A. brevis, despite the fact that GB is also the main pheromone component of A. sputator, suggesting that FB has a role in reproductive isolation. In the early part of the season, traps into which the insects could both crawl and fly captured more A. brevis than designs where the insects could only fly in. Trap design was not important later in the season. This indicates the need for future development of a trap suitable for use throughout the whole season.

title: Fine structure of antennal sensilla basiconica and their detection of plant volatiles in the eucalyptus woodborer, Phoracantha semipunctata Fabricius (Coleoptera: Cerambycidae).
abstract: The ultrastructure and distribution pattern of two types of basiconic sensilla (I and II) on the antennal flagellum of both sexes of Phoracantha semipunctata (Coleoptera: Cerambycidae) was investigated by scanning and transmission electron microscope. Both types are thin-walled multiporous sensilla and occur mostly along the anterior border of the Fl1-Fl6 flagellomeres, while on the distal flagellomeres (Fl7-Fl9) they are more evenly distributed on both surfaces. Clusters of sensilla basiconica II are found on the distal half of the anterior border of the Fl1-Fl6 flagellomeres. Sensilla basiconica I have one bipolar sensory cell with a branched distal dendrite, whereas the sensilla basiconica II contain two bipolar sensory cells with branched distal dendrites. No sexual dimorphism was found in the fine structure and distribution pattern of both types of sensilla basiconica. Responses from single sensory cells to host and non-host plant odors were examined, using gas chromatography linked with electrophysiological recordings. Most cells associated with each sensillum type were narrowly tuned, each specialized for the detection of one or two chemically related compounds. No clear functional distinction between the two morphological types of sensilla was found, although the few cells that responded specifically to non-host volatiles were associated with sensilla basiconica II.

title: Ultrastructure of antennal and posterior abdominal sensilla in Chlorophorus caragana females.
abstract: Chlorophorus caragana Xie & Wang is a destructive wood-boring beetle that damages Caragana spp. bushes and is distributed in desert areas in north-west China. Using scanning electron microscopy and transmission electron microscopy, we observed the morphology and ultrastructure of antennal and posterior abdominal sensilla in C. caragana females, to discuss the putative functions of these sensilla in host location and oviposition behaviors. In total, seven types (24 subtypes) of sensilla were located on the antenna and posterior abdomen. On the antenna, there were Böhm's bristles (BB.); four subtypes of sensilla chaetica (Ch.1-Ch.4) characterized by non-porous surfaces and sensillum-lymph cavities without dendrites; two subtypes of sensilla trichodea (Tr.1 and Tr.2) with a tip pore and dendrites surrounded by dendritic sheaths; dome-shaped sensilla (Dom.) emerging from a deep cavity with one tip pore; four subtypes of sensilla basiconica (Ba.1-Ba.4) and one type of sensilla auricillica (Au.) with a porous cuticular surface and dendrites in the sensillum-lymph cavity; and one type of sensilla styloconica (Sty.) with grooves on the cuticular wall. On the posterior abdomen, there were four subtypes of sensilla chaetica (Ch.5-Ch.8); three subtypes of sensilla trichodea (Tr.3-Tr.5); and three subtypes of sensilla basiconica (Ba.5-Ba.7; Ba.5 had no groove in the cuticular wall, Ba.6 had one tip pore, and Ba.7 was located in a cuticular cavity). The antennal sensilla were believed to be mechanosensitive, chemosensitive, and sensitive to humidity and temperature, and to play roles in mating, host location and oviposition. The abdominal sensilla are believed to be related to oviposition behaviors.

title: Sensory organs inIps typographus (Insecta: Coleoptera) — Fine structure of antennal sensilla
abstract: SummaryThe antennal sensilla inI. typographus are almost exclusively confined to the flattened terminal flagellar segment. The sensillar types have distinct distribution patterns in the three areas where they are found. Judging from the ultrastructural characteristics the following functions can be assigned to the sensillar types: chemoreception, single-walled and double-walled sensilla; chemoreception/mechanoreception, terminal-pore sensillum. Moreover there are two types of mechanoreceptors, one of which is connected to a bristle, whereas the other terminates within the cuticle of the flagellar segment.

title: New Sex Attractant Composition for the Click Beetle Agriotes proximus: Similarity to the Pheromone of Agriotes lineatus
abstract: While testing traps baited with a blend of geranyl octanoate and geranyl butanoate (pheromone components previously identified for Agriotes lineatus, Coleoptera, Elateridae) in Portugal and Bulgaria, large numbers of the closely related Agriotes proximus were captured. In the literature, two different compounds, (E,E)-farnesyl acetate and neryl isovalerate had previously been identified as pheromone components of A. proximus. Subsequent field tests, conducted in several European countries, revealed that A. proximus was weakly attracted to geranyl butanoate on its own, while A. lineatus was weakly attracted to geranyl octanoate on its own. However, the largest catches for both species were observed with a blend of both compounds. No A. proximus was caught in traps baited with the blend of (E,E)-farnesyl acetate and neryl isovalerate at any of the test sites. In electroantennographic studies, antennae of male A. proximus and A. lineatus both gave greater responses to geranyl butanoate than to geranyl octanoate, suggesting that the perception of these two compounds was similar for both species. A 1:1 blend of geranyl octanoate and geranyl butanoate can be used as a bait in traps for the detection and monitoring of both A. lineatus and A. proximus in many European countries.

title: Agriotes proximus and A. lineatus (Coleoptera: Elateridae): a comparative study on the pheromone composition and cytochrome c oxidase subunit I gene sequence
abstract: The presence of geranyl octanoate, previously found in pheromone gland extracts of Agriotes lineatus females, was also demonstrated in gland extracts of A. proximus females. Similar to A. lineatus, geranyl butanoate was present only in trace amounts in A. proximus female gland extracts. In air entrainment samples of female A. lineatus and A. proximus beetles, the relative ratio of geranyl butanoate and geranyl octanoate was higher than that in gland extracts. In addition, comparison of a segment of the mitochondrial cytochrome c oxidase subunit I gene of feral specimens of A. lineatus and A. proximus showed >99% similarity. Both pheromone profile and nucleotide sequence analysis delineate close relationship between the investigated taxa and postulate taxonomic revision. Further studies on sympatric populations of A. lineatus and A. proximus are underway to investigate and better understand possible processes of species diversification.

title: The molecular identification and genetic diversity of economically important wireworm species (Coleoptera: Elateridae) in Canada
abstract: Click beetle larvae (wireworms) are significant crop pests in Europe and North America. In Canada, there are ~30 economically important species which are morphologically difficult to identify, but for which sequence data are lacking. Accurate knowledge of damage-causing species and the population genetics and phylogeography of elaterids will provide insight into their sustainable management. Here, we use interspecific variation in mitochondrial 16S rRNA as a robust method of identification, consider the intra- and interspecific genetic variation of some important Canadian wireworm pests and assess the genetic structure and isolation by distance for a re-emerging major pest species, Hypnoidus bicolor Eschscholtz. Wireworms were sampled from Canada and the USA, identified as morphospecies, and sequenced at the 16S rRNA region (294–442 bp). Within some species unusually high intraspecific genetic distances between samples suggested the possibility of cryptic wireworm species or misidentifications, though this was <1 % for most species. Phylogenetic analyses gave some indication of the likely identity of these ambiguous samples. There was a significant correlation between genetic and geographic distance and significant genetic structuring within and between H. bicolor populations, which appeared to be composed of two species comprising several haplotypes. These data provide a starting point for determining the distribution of damage-causing species throughout Canada. The inclusion of data from other nuclear and mitochondrial loci, and use of sequence data from known adult samples, would further aid identification and relationships of wireworm species.

title: Identification of pheromones and optimization of bait composition for click beetle pests (Coleoptera: Elateridae) in Central and Western Europe.
abstract: Based on analysis of pheromone gland extracts, highly attractive new baits have been developed for three click beetle pests. That for Agriotes brevis is a mixture of geranyl butanoate and (E,E)-farnesyl butanoate, and that for A rufipalpis and A sordidus contains geranyl hexanoate alone. From known data from species populating Russia, optimized bait compositions for species in Central and Western Europe were developed as follows: geranyl octanoate + geranyl butanoate for A lineatus, geranyl isovalerate for A litigiosus, geranyl hexanoate + geranyl octanoate for A obscurus, geranyl butanoate alone for A sputator and (E,E)-farnesyl acetate alone for A ustulatus. Although slight differences were found in gland contents with A litigiosus var laichartingi and fenotypus typicus, nevertheless there were no differences in response to the optimum bait. There were no differences in pheromone composition or response to the optimized bait between the two morphological forms ('black' and 'red') of A ustulatus. As a result of these studies, highly effective pheromone baits are now available for monitoring and population reduction in all important pest click beetle species in Central and Western Europe.

title: Pheromones and attractants of click beetles: an overview
abstract: The study of pheromones of click beetles was started with the objective of applying similar methods in IPM strategies for the control of wireworms, based on the similar experience gained from the widely used moth pheromones. A brief overview is presented on the identification of click beetle pheromones, new questions arising in the categorization of these pheromones into sex or aggregation pheromones, options for the development of female-targeted lures, and application perspectives.

title: Determination of Agriotes obscurus (Coleoptera: Elateridae) sex pheromone attraction range using target male behavioural responses
abstract: A study was conducted to determine the attractive range of traps baited with Agriotes obscurus pheromone to male beetles in both still air and wind conditions. This information is crucial for evaluating the potential of mass trapping when aiming to reduce beetle populations. Groups of 10 beetles were released at 14 points spaced 1 m apart along a linear track, at one end of which was a pheromone and wind source. Beetle response to the pheromone and/or wind was recorded 150 s after release and characterized as orienting either towards or away from the pheromone and/or wind source. Data analysis indicated the attraction range of the sex pheromone is <5 m in still air, which is considerably lower than estimates from previous studies and emphasizes the challenge of mass trapping this species in the field. The attraction range increased when there was air flow. Unexpectedly, not all male beetles respond to the pheromone, and beetles are inclined to move downwind even in the presence of pheromone. The latter finding suggests that wind direction may influence beetle dispersal and mate finding in the field. The implications of these results for determining the efficacy of mass trapping as a management approach are discussed.

title: The Addition of a Pheromone to a Floral Lure Increases Catches of Females of the Click Beetle Agriotes ustulatus (Schaller) (Coleoptera: Elateridae)
abstract: Agriotes ustulatus is an economically important click beetle in Europe. A female-produced pheromone, (E,E)-farnesyl acetate, has been identified and is used for monitoring and detecting males. More recently, a floral lure targeting females with modest, but significant, activity has been described. Based on preliminary data, we hypothesized, that similar to the effects on the congeneric A. brevis, addition of the pheromone to the floral lure should improve female A. ustulatus catches. Also, as click beetles have been reported to respond to white light, we studied possible interactions between visual and chemical cues. In field trials, the addition of the synthetic pheromone to the floral lure resulted in a dramatic increase in the number of females trapped, whereas male catches remained unaffected and equal to those in traps baited with pheromone only. A white visual cue did not influence trap catches. Maximum catches of both sexes of A. ustulatus can be achieved using the pheromone and the floral lure inside the same trap. Furthermore, the compounds can be formulated in a single polyethylene bag dispenser, making handling of the trap easier. Due to a much larger proportion of females in the catch, this improved trap may be a promising tool for semiochemical-based, environmentally sound agricultural practice against this important pest.

title: Sex Pheromone of Agriotes acuminatus (Stephens, 1830) (Coleoptera: Elateridae)
abstract: The click beetle species Agriotes acuminatus is distributed in open deciduous forests throughout a large area in Europe. In order to identify its sex pheromone, gland extracts of female beetles were investigated by using GC/MS. Neryl butanoate and 2,6-dimethyl-(Z,E)-2,6-octadien-1,8-diol dihexanoate, in a ratio of approximately 1:5, were the only volatile compounds present in the extracts. Structures of both esters were confirmed by synthesis. Field experiments revealed a strong attraction of A. acuminatus males towards neryl butanoate, which could be synergistically enhanced by addition of 2,6-dimethyl-(Z,E)-2,6-octadien-1,8-diol dihexanoate. The latter compound alone did not show any attractive effect. While all Agriotes spp. investigated to date use geranyl and/or (E,E)-farnesyl esters as sex pheromones, the nerol derivatives of A. acuminatus are the first (Z)-2-configurated pheromones within this genus.

title: Female Responses to Synthetic Pheromone and Plant Compounds in Agriotes brevis Candeze (Coleoptera: Elateridae)
abstract: Traps baited with synthetic pheromone components of Agriotes brevis [geranyl butanoate + (E,E)-farnesyl butanoate] captured significantly higher numbers of not only male, but also female beetles, compared to unbaited controls. Catches of both sexes showed a clear positive relationship with increasing doses. In electroantennogram tests, antennal responses of females and males to a number of known Agriotes pheromone components, identified from pheromone glands, showed a similar trend, with geranyl butanoate eliciting the strongest responses. This suggests that the female and male A. brevis antennae are similar with respect to the perception of pheromone compounds, and female beetles have the sensory capabilities to perceive the pheromone components which they produce. Addition of the plant-derived compounds (Z)-3-hexenyl acetate, methyl benzoate, (Z)-3-hexenol and methyl salicylate (identified earlier from foliage as attractive for A. brevis) to the synthetic pheromone significantly increased catches. All the above results suggest that geranyl butanoate and (E,E)-farnesyl butanoate are constituents of an aggregation pheromone of A. brevis, in contrast to the general view of click beetle pheromones being “classical” sex pheromones. These findings could be useful for more precise monitoring and forecasting of damage, based on female catches.