Responses of the infrared sensilla of Melanophila acuminata (Coleoptera: Buprestidae) to monochromatic infrared stimulation

The pit organs of the beetle Melanophilaacuminata were stimulated with monochromatic infrared radiation using a continuous wave CO overtone infrared laser. Best sensitivity was in the wavelength range 2.8–3.5 μm. In this range a stimulus intensity of 14.7 mW cm⁻² was sufficient to generate single action potentials. At a wavelength of 5 μm receptor performance significantly decreased. An increase in stimulus intensity caused a decrease in response latency and an increase in the number of action potentials elicited. At a given wavelength (3.4 μm) the dynamic amplitude range of action potential responses covered 12 dB. At high stimulus intensities (94.2 mW cm⁻²) a stimulus duration of 4 ms was sufficient to generate one to two action potentials and a stimulus duration of 60 ms already caused response saturation (with up to nine action potentials). In a repetitive stimulus regime distinct receptor potentials were visible up to a frequency of 600 Hz. Accepted: 18 March 2000     

Sensitivity threshold and response characteristics of infrared detection in the beetle Melanophila acuminata (Coleoptera: Buprestidae)

The minimum detection threshold of the infrared sensitive beetle, Melanophila acuminata, was measured with a helium-neon laser that emitted light at a wavelength of 3.39 microm. Extracellular recordings were taken both at the pit organ responsible for detection and at the interganglionic connectives in the thorax of the beetle. At the pit organ, generator and action potentials from single neurons were measured with a sharpened tungsten electrode. At the connectives that linked the fused second meso-/metathoracic and prothoracic ganglia, compound action potentials were measured with a tungsten hook electrode that encircled the connective. The latter recordings confirmed conveyance of infrared information through specific pathways to rostrally-situated sites in the nervous system of the beetle. The 50% probability irradiance threshold at which action potentials were elicited from the receptor and connectives occurred at 17.3 and 14.6 mW/cm(2), respectively. In addition to sensitivity threshold, several other characteristics of the response were quantified including dependence of generator potential latency, generator potential duration, spike frequency, and spike latency on irradiance, dependence of response strength (spike count) on exposure time, and flicker fusion frequency. The ability to detect infrared radiation is rare in nature, and these results provide valuable information necessary to understand this unique sensitivity.     

The photomechanic infrared receptor for the detection of forest fires in the beetle Melanophila acuminata (Coleoptera: Buprestidae)

We recorded from single units of individual sensilla of the thoracic infrared (IR) pit organs of Melanophila acuminata. When the organ was stimulated with a thermal radiator whose emission spectrum was similar to that of a typical forest fire, units responded phasically with up to seven spikes within 30–40 ms at a radiation power of 24 mW cm⁻². In the experiments all wavelengths shorter than 1.6 μm were excluded by a longpass IR filter. Response latencies were about 4 ms and initial impulse frequencies were up to 250 impulses per second (ips). A single spike could be generated even when stimulus duration was only 2 ms. Reduction of total radiation power from 24 mW cm⁻² to 5 mW cm⁻² resulted in increased response latencies of 5–6 ms and the occurrence of only two to three spikes. Initial impulse frequencies decreased to 125 ips. According to our physiological results and calculations, Melanophila should be able to detect a 10-hectare fire from a distance of 12 km. Mechanical stimuli also evoked responses of the IR sensilla. All present morphological and physiological findings lead to the conclusion that the IR receptors of Melanophila must function by means of a hitherto undescribed photomechanic mechanism. Accepted: 1 November 1997     

Electrophysiological characterization of the multipolar thermoreceptors in the "fire-beetle" Merimna atrata and comparison with the infrared sensilla of Melanophila acuminata (both Coleoptera,Buprestidae)

A thermosensitive multipolar neuron innervates each of the four abdominal receptors of the Australian buprestid beetle Merimna atrata. The neuron is spontaneously active within a broad range of body temperatures (tested between 10°C and 40°C). We heated the receptors with a red diode laser (=0.66 µm) at intensities ranging from 5.3 mW cm^–2 up to 1.3 W cm^–2. In general, warming caused an increase of receptor activity. Peak discharge frequencies were reached 100–300 ms after onset of irradiation. After peak frequencies were reached, distinct adaptation took place within seconds. A linear increase in irradiation intensity caused an exponential increase in peak frequencies. Lowest threshold was found to be at 40 mW cm^–2 where latencies were 47 ms. At the highest intensity tested (1.3 W cm^–2), peak frequencies increased up to about 300 Hz and latencies decreased to 24 ms. Considering the pyrophilous behaviour of Merimna and the morphological data from previous studies, our results support the hypothesis that the abdominal receptors are infrared receptors. We also recorded the responses of the photomechanic infrared sensilla of Melanophila acuminata under the same experimental conditions. These results show that the photomechanic sensillum of Melanophila has a higher sensitivity, and that the latencies are considerably shorter.     

The analysis of the mechanosensory origin of the infrared sensilla in Melanophila acuminata (Coeloptera; Buprestidae) adduces new insight into the transduction mechanism

The thoracic infrared (IR) sensilla of the pyrophilous jewel beetle Melanophila acuminata most likely have evolved from hair mechanoreceptors (sensilla trichodea). To further elucidate the sensory transduction mechanism, the morphology of IR sensilla and of neighbouring hair mechanoreceptors was investigated by using conventional electron microscopical techniques (SEM, TEM) in combination with focused ion beam milling (FIB). It was assumed that any deviation from the bauplan of a sensillum trichodeum is of particular concern for the transduction of IR radiation into a mechanical stimulus. Thus, the structures supposed to be relevant for stimulus uptake and transduction were homologized. Compared to a hair mechanoreceptor, an IR sensillum shows the following special features: (i) the formation of a complex cuticular sphere instead of the bristle; the sphere consists of an outer exocuticular shell as well as of an inner porous mesocuticular part. (ii) The enclosure of the dendritic tip of the mechanosensitive neuron inside the sphere in a fluid-filled inner pressure chamber which is connected with a system of microcavities and nanocanals in the mesocuticular part. Hence we propose that an IR sensillum most probably acts as a microfluidic converter of infrared radiation into an increase in internal pressure inside the sphere which is measured by the mechanosensitive neuron.     

The infrared receptor of Melanophila acuminata De Geer (Coleoptera: Buprestidae): ultrastructural study of a unique insect thermoreceptor and its possible descent from a hair mechanoreceptor

The paired infrared organs of Melanophila acuminata consist of 50-100 sensilla situated at the bottom of a pit next to the coxae of the mesothoracic legs, where no exocuticle is developed. Each sensillum is accompanied by a wax gland and has a cuticular lens-like spherule (diameter 12-15 mum) bulging out with its upper hemisphere above the surface, covered only by a thin cuticle of about 1 mum. Distal processes of two enveloping cells surround the entire spherule in the form of a flattened protoplasmatic layer with the exception of a small apical stalk connecting the spherule to the outer cuticle. The spherule is innervated by a single sensory neuron of the ciliary type which is anchored ventrally with the distal tip of its cylindrical and unbranched DOS in the spherule. The insertion of the dendrite, which contains a well-developed tubular body, is always eccentric like in a hair mechanoreceptor (sensillum trichodeum) and there is no evidence of any optical function of the spherule. Three enveloping cells exist, but only one - probably the trichogen cell - forms a relatively small outer receptor lymph cavity. In the posterior wall of the pit - where exocuticle is developed - so-called suppressed systems can be found which remain completely below the cuticle with their otherwise well-developed spherules. Additionally, there is a tendency towards basally flattening and longitudinally stretching of spherules which are situated more peripherally. They strongly resemble the basal regions of hair mechanoreceptors (sensilla trichodea) in their immediate neighbourhood which are also accompanied by wax glands. Because of the existence of these transitional stages and the great ultrastructural resemblance between infrared receptors and hair mechanoreceptors concerning the bauplan of the sensory neurons and their mode of innervating the cuticular apparatus, we conclude that the infrared sensilla are probably derived from hair mechanoreceptors. Based on these results and transmission measurements of infrared radiation through the cuticular components of the organ, a model of the possible function of the infrared receptor is presented.     

Antennal sensilla of the click beetle,Melanotus villosus (Geoffroy) (Coleoptera: Elateridae)

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 Böhm 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.     

Antennal sensilla of the ground beetle Bembidion lampros Hbst (Coleoptera, Carabidae)

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 Böhm 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.     

Fine-structure of the compound eye of the buprestid beetle Curis caloptera (Coleoptera, Buprestidae)

Curis caloptera is a buprestid beetle, which is active in bright sunlight. Its eye, like that of many other diurnal arthropods, is of the apposition type, in which dioptric apparatus and receptor layer are not separated by a region devoid of pigment. Perhaps to prevent damage by U. V.-radiation, the cornea is relatively thick (approximately 90 micron) and crystalline cones are of the "eucone-type". In each ommatidium the cone cell extensions occupy regular positions between the 8 retinula cells and reach down to the basement membrane where they end in bulbous swellings and contain grains of screening pigment. Pigment grains, slightly smaller than those present in the primary pigment cells, are also found within the retinula cells. Although the rhabdom possesses a uniform diameter of approximately 2 micron over its entire length of almost 300 micron, the number of rhabdomeres contributing to the rhabdom varies and depends on the level at which the rhabdom is sectioned. At the distal end, only one retinula cell possesses a rhabdomere; the same holds true for the proximal end, where a different rhabdomere (with microvilli at right angles to those of the distal cell) dominates. One retinula cell, of darker appearance in electron micrographs, occupies a distal position in each ommatidium and remains preferentially oriented within a sector of 60 degrees irrespective of the ommatidial axis. The ommatidial axis itself was found to vary 235 degrees. We provide circumstantial evidence for the view that the cell in question could be a U. V.-receptor with a role to play in an unambiguous determination of the E-vector. Separate bundles, each containing 8 axons, pass through the basement membrane together with 1 or 2 tracheoles. A traceheal tapetum is not developed.     

红缘吉丁（鞘翅目： 吉丁虫科）触角感器的扫描电镜观察

对红缘吉丁Buprestis fairmairei Thery触角感器的超微结构、类型和分布进行了研究。结果表明,红缘吉丁触角具有3种刺形感器、2种毛形感器、4种锥形感器和1种芽孢感器。触角感器在每节上的数量和分布不同。     

Rising temperatures explain past immigration of the thermophilic oak-inhabiting beetle Coraebus florentinus (Coleoptera: Buprestidae) in south-west Germany

Global warming enables the immigration of species previously absent from a given region. Coraebus florentinus (Coleoptera: Buprestidae) is a beetle with a Mediterranean distribution that has expanded its northern range margin northwards within the last 30 years. It develops in branches and shoots of oak (Quercus spp.) and is considered a pest in Mediterranean countries. By modelling the current spatial distribution of C. florentinus using three independent modelling approaches (generalised linear models, boosted regression trees, maximum entropy modelling) we identified abiotic factors which explain its current spatial distribution (1991–1999) in south-west Germany and reconstructed its immigration into Germany since 1950. All modelling approaches suggest that monthly maximum temperatures determined the range margin of the species in south-west Germany from 1991 to 1999. Occurrence probabilities increased exponentially with mean maximum temperatures higher than 10 °C in March and 22 °C in June. Mean precipitation in May also seems to be important for the species occurrence, particularly in regions where oaks grow on poor sandy soil; however, this generally plays a minor role. All of these environmental conditions are linked to higher reproduction of C. florentinus on oaks in warm and dry habitats, as reported from southern Europe. We show that climatic conditions for the beetle have improved significantly in south-west Germany since 1950, which is most likely the reason for the northward shift of its range margin. Our modelling results suggest a further range expansion of the beetle in Central Europe.     

Ultrastructure of sensilla of the female mountain pine beetle,Dendroctonus ponderosae hopkins (Coleoptera : scolytidae)

The objective of this study is to provide a morphological foundation for electrophysiological studies on the sensilla of D. ponderosae. The sensilla on the antennae, labial and maxillary palps, galeae and fore-tarsi are described. The antennal club has several types of sensilla: (1) multiporous non-socketed pegs of varying lengths innervated by 2 neurons, (2) uniporous socketed pegs innervated by 5 neurons, (3) pegs innervated by only 1 neuron at the base, (4) tapered uniporous cones innervated by 4 neurons, and (5) fluted multiporous, non-socketed cones innervated by 4 neurons. All hairs on the fore-tarsi are innervated by 1 neuron at the base. The labial and maxillary palp-tips have: (1) digitiform organs, (2) campaniform organs, (3) uniporous, socketed pegs innervated by 5 neurons, and (4) non-porous pegs innervated by 3 neurons. Two small, uniporous, socketed pegs innervated by 4 neurons, are set into the maxillary palp-tip sidewall, and a single, sharp-tipped peg, innervated by 1 neuron, is found on the tip. These 2 types are not seen on the labial palps. The ultrastructure of each type of sensillum found on both the maxillary and labial palps is similar; however, the number of uniporous and non-porous pegs on the labial palps is about half those of the maxilla. The maxillary galeae each have 3 types of sensilla: (1) numerous pegs of various sizes innervated by 1 neuron, (2) a single, possibly uniporous socketed peg innervated by 5 neurons, and (3) another single non-porous non-socketed peg innervated by 2 neurons.     

Revision of the aerea group of Chrysobothris (Coleoptera: Buprestidae)

Abstract. The aerea group of the genus Chrysobothris Eschscholtz, as characterized for the first time, includes eight species which occur in the south-western United States and in Mexico. The complicated taxonomic history and confused identity of some species is discussed in depth. Four Mexican species are redescribed in detail from type material: aerea Chevrolat, quadriplagiata Water-house, simplex Waterhouse, stellifera Waterhouse. Lectotypes are designated for the last two species. C.costifrons Waterhouse is considered to comprise three subspecies; two, C.c.rubiterga and C.c.baja are newly described. The remaining species in the group are C.bispinosa, chalcophoroides and serripes . Illustrations and keys to species and subspecies are provided.     

The conserved mitochondrial genome of the jewel beetle (Coleoptera: Buprestidae) and its phylogenetic implications for the suborder Polyphaga

In this study, we sequenced the mitochondrial (mt) genome of Agrilus mali (Coleoptera: Buprestidae) using next-generation sequencing, and accordingly annotated 13 protein-coding, 22 tRNA, and 2 rRNA genes and a 1458-bp non-coding region. Comparative analysis indicated that the mt genome of A. mali is relatively conserved, with a typical gene content and order identical to those of other coleopterans. However, the newly sequenced mt genome is characterized by a relatively higher A + T content compared with that of other species within the family Buprestidae. Phylogenetic analysis based on Bayesian inference revealed that the evolutionary relationship among the six infraorders of the suborder Polyphaga is (Scirtiformia + (Elateriformia + ((Scarabaeiformia + Staphyliniformia) + (Bostrichiformia + (Cucujiformia))))). However, the topology indicated that the family Buprestidae is a sister group to other Polyphaga infraorders, excluding Scirtiformia as a monophyly, and thus the monophyly of Elateriformia was not supported. This study not only presents the mt genome of a species in the family Buprestidae and a comparative analysis of jewel beetles but also examines the contribution of mt genomes in elucidating phylogenetic relationships within the suborder Polyphaga of Coleoptera.     

Antennal sensilla and sexual dimorphism of the adult ladybird beetle Semiadalia undecimnotata Schn. (Coleoptera: Coccinellidae)

The antennal receptors of the adult male and female ladybird beetle, Semiadalia undecimnotata (Coleoptera: Coccinellidae), were examined by scanning and transmission electron microscopy. Twelve types of receptors were characterized and grouped into 5 morphological classes: Böhm, trichoid, coeloconic, basiconic, and chetiform sensilla. Sensory function was determined on the basis of sensillar ultrastructure and electrophysiological response. Olfactory sensilla are confined in both sexes to the 2 terminal antennal segments. In contrast, gustatory and mechanosensitive organs are present along the entire length of the antennae. Sexual dimorphism of antennal receptors is limited to the latter 2 functional classes. The principal characteristics of this dimorphism are the following: a) males possess 540 sensilla (all types), while females possess only 500; b) males exhibit 2 types of taste receptors not present in females; c) females exhibit one type of mechanoreceptor absent in males; d) the 3 sex-specific types of sensilla, which occupy the same position in males and females, are confined to the inner side of the antennae. The possible role of male-specific sensilla in intersexual communication is discussed.     

Ultrastructure structure of antennal sensilla of carabid beetle Carabus elysii Thomson, 1856 (Coleoptera: Carabidae)

The sensilla type, number and distribution in male and female adults of Carabus elysii Thomson, 1856 (Coleoptera: Carabidae) were studied using scanning electron microscopy. The results showed that there are seven categories and 12 types of sensilla in C. elysii adults: three types of S.Ch, three types of S.T, two types of S.B and one each of B.B, S.Co, S.Ca and S.Cam. There is no difference between male and female in the types of sensilla. Apart from the significant difference in the number and distribution of S.B.2, S.Co and S.Ca between male dorsal and ventral surfaces, there are no significant differences between male and female antennae. In general, the number of sensilla in females is larger than that in males. The results provide a basic reference for future ultrastructure, electrophysiological, and comparative behavioral studies of Carabus species.     

Morphology of antennal sensilla of the brown spruce longhorn beetle,Tetropium fuscum (Fabr.) (Coleoptera: Cerambycidae)

The antennal sensilla of the brown spruce longhorn beetle, Tetropium fuscum (Fabr.) (Coleoptera: Cerambycidae) were examined with particular focus on the sensilla present on the apical flagellomere. T. fuscum antennae are composed of 11 segments, namely the scape, pedicel, and nine flagellomeres. Nine types of sensilla were observed: three types of sensilla chaetica, sensilla trichodea, two types of sensilla basiconica, grooved peg sensilla, thick-walled sensilla, and Böhm bristles. Seven of these types were present on the apical flagellomere, the exceptions were sensilla chaetica type 3 and Böhm bristles. There were no significant differences in the distribution or density of sensilla present on the ninth flagellomere of males and females, except that males had significantly more sensilla chaetica type 1, which are put forward as the putative contact chemoreceptors for T. fuscum.     

柑桔爆皮虫卵巢发育动态

本研究利用室内饲养成虫,对柑桔爆皮虫的蛹及正常取食和交配、正常取食但未交配以及正常交配但未取食三种处理的雌成虫的卵巢发育进行了系统观察。结果显示：该虫具有1对卵巢,每侧有5根卵巢管。前两种处理的雌虫卵巢管均能正常发育,成虫寿命在30天左右; 没有取食的雌虫寿命只有7天左右,在其卵巢管的生长区和成熟区均无卵形成。根据卵巢的形状、卵的产生过程、卵巢萼内有无卵粒以及卵黄沉积情况等将卵巢发育程度分为6个级别,即发育初期（0级）、卵黄沉积前期(Ⅰ级)、卵黄沉积期(Ⅱ级)、成熟待产期(Ⅲ级)、产卵盛期(Ⅳ级)和产卵末期(Ⅴ级)。每头雌虫最高怀卵量在140粒左右,根据雌虫怀卵量变化趋势,推测正常取食和交配的柑桔爆皮虫雌虫在出孔后10天左右开始产卵,产卵历期可达22天左右。据此提出该虫卵巢管发育到成熟待产期(Ⅲ级)之前（即羽化出孔后10天之内）为出孔成虫的防治适期。