Lehr's fields of campaniform sensilla in beetles (Coleoptera): Functional morphology. II. Wing reduction and the sensory field

Loss of the flight ability and wing reduction has been reported for many taxa of Coleoptera. If elytra are closed, their roots are clenched between the tergum and the pleuron, forces applied to the elytra can not be transmitted to the field of campaniform sensilla situated on the root. That is why it is plausible to assume that the field becomes redundant in non-flying beetles. We examined the relationships between the hind wing reduction and characters of this mechanosensory field in beetles of six families. We measured the size of the elytron, that of the hind wing and counted the number of sensilla in the sensory field. Mesopterous non-flying beetles retain one half to one third of sensilla present in macropterous species of the same body size. Further reduction of the sensory field in brachypterous species is obvious, but sensilla are still present in insects with strongly reduced wings, as long as their elytra are separable and mesothoracic axillaries are present. Complete loss of sensilla coincides with the existence of a permanent sutural lock. However, some beetles with permanently locked elytra and absence of axillaries still retain few campaniform sensilla. A very special case of an extreme wing modification in feather-wing beetles is considered. No sensilla were revealed either on the root of the elytron or on the basal segment of such fringed wings in flying ptiliid species.     

Lehr's fields of campaniform sensilla in beetles (Coleoptera): Functional morphology. III. Modification of elytral mobility or shape in flying beetles

Some flying beetles have peculiar functional properties of their elytra, if compared with the vast majority of beetles. A “typical” beetle covers its pterothorax and the abdomen from above with closed elytra and links closed elytra together along the sutural edges. In the open state during flight, the sutural edges diverge much more than by 90°. Several beetles of unrelated taxa spread wings through lateral incisions on the elytra and turn the elytron during opening about 10–12° (Cetoniini, Scarabaeus, Gymnopleurus) or elevate their elytra without partition (Sisyphus, Tragocerus). The number of campaniform sensilla in their elytral sensory field is diminished in comparison with beetles of closely related taxa lacking that incision. Elytra are very short in rove beetles and in long-horn beetles Necydalini. The abundance of sensilla in brachyelytrous long-horn beetles Necydalini does not decrease in comparison with macroelytrous Cerambycinae. Strong reduction of the sensory field was found in brachyelytrous Staphylinidae. Lastly, there are beetles lacking the linkage of the elytra down the sutural edge (stenoelytry). Effects of stenoelytry were also not uniform: Oedemera and flying Meloidae have the normal amount of sensilla with respect to their body size, whereas the sensory field in the stenoelytrous Eulosia bombyliformis is 5–6 times less than in chafers of the same size but with normally linking broad elytra.     

Double rotation of the opening (closing) elytra in beetles (Coleoptera)

Transient movements of the elytra (opening and closing) were filmed in beetles tethered from below. A total of 39 specimens of 18 species representing 11 families were examined. Bright markers glued to the elytra were traced frame by frame. Body-fixed 3D traces of apical and shoulder markers were reconstructed. Shapes of traces reflected different steps of elytral movement and different types of flight. Flat circular arcs were fitted to scattered traces using the least square method. The rotation axis of the apical marker was always directed at the contralateral side. The trace of the shoulder marker was, as a rule, non-parallel to the apical trace. Usually, the shoulder marker on the costal edge of the elytron uniformly supinated in the course of adduction of the apical marker. Traces of opening and closing coincided, hence the double rotation of the elytron had one degree of freedom. The elytron to body articulation in beetles is, presumably, a spherical mechanism with two separate but linked drives for a broad swing during opening (closing).     

DISTRIBUTION OF TRABECULAE AND ELYTRAL SURFACE STRUCTURES OF THE HORNED BEETLE, ALLOMYRINA DICHOTOMA (LINNÉ) (COLEOPTERA: SCARABAEIDAE)

Abstract To clarify the dynamic construction of Allomyrina dichotoma (Linné) elytra, the distribution of trabeculae and surface structures has been investigated using scanning electron microscopy and transmitted light. There are solid trabeculae in the elytron and under penetrating light these can be seen as black dots. It is clear that trabeculae arrangement is almost entirely irregular throughout the elytron, except for some approximately straight alignment near some trachea. This irregular arrangement is different from the longitudinal rows of striations that are well known in other species, and there are no hollowed striae (punctures) on the elytral surface of A. dichotoma . Throughout the internal architecture of the elytron, there are mesh-like (honeycomb) structures. Each honeycomb usually has 1–2 trabeculae mainly distributed at the corners of the honeycomb. The number of trabeculae present on each honeycomb is dependent on the size of the honeycomb.     

Indirect closing of elytra by the prothorax in beetles (Coleoptera): general observations and exceptions

Voluntary movements of the prothorax and the elytra in tethered flying beetles and manually induced movements of these parts in fresh dead beetles were recorded in 30 species representing 14 families. Participation of prothoracic elevation in the closing of the elytra was demonstrated in three ways. (i) The elevation was always simultaneous with elytral closing, in contrast to depression and elytral opening; a rare exception occurred in Lucanus cervus, whose elytra sometimes started to close before the cessation of wing strokes and the elevation of the prothorax. (ii) The manipulated elevation always induced closing of the spread elytra; the mechanical interaction between the hind edge of the pronotum and the roots of the elytra is a universal mechanism of closing the elytra in beetles. (iii) The prevention of pronoto-elytral contact in live beetles by the excision of the hind edge of the pronotum in front of the root prevented elytral closing after normal flight. Exceptions to this rule included some beetles that were able to close their elytra after such an excision: tiger beetles and diving beetles (seldomly) and rose chafers (always). This ability in Adephaga may be explained by attachments of the muscle actuating the 4th axillary plate, which differ from the attachments in Polyphaga. Cetoniinae open their elytra only by a small amount. It is proposed that their small direct adductors in combination with the elasticity of the sclerites are enough to achieve elytral closing without additional help from the prothorax.     

Sensory organs of the antennae and mouthparts of beetle larvae (Coleoptera)

The sensilla located on the antennae and maxillary and labial palps of the larvae of 64 beetle species from 22 families were studied using electron microscopy. The larvae of beetles living in different habitats and having different trophic specializations possess a uniform structure of the sensory organs. They are composed of two groups of sensilla on the apical and subapical segments of the antennae, one apical group of sensilla on both maxillary and labial palps, and one or several digitiform sensilla on the lateral surface of the maxillary and, occasionally, labial palp. The external morphology of the sensory organs is adaptive and represents modifications of the initial type. Band-shaped sensilla or placoid sensilla, clearly different from the initial sensory organs, appear in some taxa as rare exceptions, while other groups display either partial reduction of the receptor organs (Gyrinidae) or reduction of the cuticular parts of the sensilla (Cantharidae).     

Mechanisms Modeling the Double Rotation of the Elytra in Beetles (Coleoptera)

We recorded transient movements,i.e.opening and closing,of beetle elytra.The beetles were tethered from below and filmed under a skew mirror; two markers were glued on each elytron at the apex and at the base.Body-fixed 3D traces of the apical and basal markers were reconstructed.The trace of the basal marker was,as a rule,non-parallel to the apical trace.The costal edge of the elytron uniformly supinated in the course of adduction of the apical marker.We found two essential attributes of double rotation:(1) the elytron to body articulation is approximately a spherical mechanism; (2) transient opening and closing possess single degree of freedom.The double rotation was modeled with two mechanisms:(1) a flexagon model of the Haas and Wootton's type simulated the elytral movement relative to the movement of one facet of the flexagon; (2) a screw and nut model provided traces as two sectors of a helical thread,one sector was phase shifted with respect to other one.Screw guideways in a spherical mechanism give rise to discrepancies.Exact solution for a spherical mechanism with two guideways was proposed.The modeling revealed the attribute (3):the elytron is actuated by two linked but differently directed drives.Experimental investigations on the elytron to body articulation may be oriented at search of those mechanisms.     

Geographical variation of elytral spot patterns in the phytophagous ladybird,Epilachna vigintioctopunctata (Coleoptera: Coccinellidae) in the Province of Sumatera Barat,Indonesia

Geographical variation in the elytral spot patterns of a phytophagous ladybird, Epilachna vigintioctopunctata, was studied in the Province of Sumatera Barat, Indonesia. Populations of E. vigintioctopunctata were divided into four major groups (I–IV) by the incidence of spot pattern variations. Group I, occurring in the coastal plains and inland lowlands, and Group IV, confined to the highlands, were the extremes of the spot pattern variations, the latter had many more non-persistent spots and confluences with larger body size and advanced melanism than the former. These two groups were connected with each other via the intermediate groups. A positive relationship was detected between the elevations of sample sites and the average number of non-persistent spots per elytron. Consequently, present results favor the view that the two previously recognized forms of E. vigintioctopunctata (formae A and B inKatakura et al., 1988) represent a complicated intraspecific variation rather than two distinct sibling species. Elytral spot pattern variations were not different between the sexes or between the beetles collected from different kinds of host plants.     

A morphological investigation of Culicoides spp. biting midges (Diptera: Ceratopogonidae) from the Caribbean.

Features of the antennae, maxillary palps, and mouthparts of the females of seven species of Culicoides spp. biting midges collected from a montane rainforest site in Trinidad, West Indies, were studied by light and scanning electron microscopy. Comparisons were made with two British species, Culicoides impunctatus and Culicoides nubeculosus. Species-specific differences were demonstrated in the camber and pitch of mandibular teeth, the size and shape of the subapical labral sensilla, the size and depth of the palpal sensory pit, and the number and shape of heads of the palpal sensilla. Counts of sensilla coeloconica and palpal sensilla were suggested as being contributory features for the prediction of host preference, indicating that Culicoides darlingtonae, Culicoides glabellus, Culicoides insinuatus, Culicoides paraensis, and Culicoides pseudodiabolicus were probably mammalophilic species. The host preferences of Culicoides heliconiae and Culicoides flavivenula could not be determined accurately.     

Distribution and fine structure of antennal olfactory sensilla in Japanese dung beetles,Geotrupes auratus Mtos. (Coleoptera : Geotrupidae) and Copris pecuarius Lew. (Coleoptera : Scarabaeidae)

The distribution and fine structure of olfactory sensilla on the antennal flagella of the Japanese dung beetles, Geotrupes auratus (Coleoptera : Geotrupidae) and Copris pecuarius (Coleoptera : Scarabaeidae) were studied by scanning and transmission electron microscopy. In both types of dung beetles, sensilla on the antennal segments were most abundant on the apical 3 lamellar segments, where sensilla basiconica were particularly concentrated. The sensilla were solely concentrated in the central part of the distal side of both the 9th and 10th segments in G. auratus and the 7th and 8th segments in C. pecuarius, respectively. The numbers of sensilla in these areas (channels) of the 9th and 10th segments in G. auratus were approximately 4,500 and 3,000, respectively. In C. pecuarius, there were about 1,900 sensilla on the 7th segment and l,700 sensilla on the 8th. The cuticles of the sensilla in both species were perforated by numerous elongate pores, with a pore density of about 45/ μm² in G. auratus and 30/ μm² in C. pecuarius. Each sensillum basiconicum in C. pecuarius was generally associated with 2 sensory neurons. The sensory cilia passed into the sensillum lumen and branched profusely, occupying most of its space. On the basis of the fine structure and dense location, these sensilla are considered to have an olfactory function for food detection.     

Antennal sensillar equipment in closely related predatory wasp species (Hymenoptera: Philanthinae) hunting for different prey types

Despite its potential value in phylogenetic and ecological studies, the morphology of antennal sensilla has rarely been compared quantitatively within the Apoidea. Here, through a scanning electron microscopy analysis, we provide an inventory of different types of antennal sensilla and compare their morphology across 10 species of predatory wasps (Crabronidae: Philanthinae) including species that hunt exclusively either on beetles or on bees to feed their larvae. A sensilla-free area was found on the apical flagellomer of all but two species, and its shape and size appear to be useful for separating Philanthini from Cercerini within the subfamily. A total of eight types of sensilla (sensilla placoidea, sensilla basiconica, two types of pit organs, sensilla coelocapitula and three types of sensilla trichoidea) were found in all species, and an additional rarer type (grooved peg sensilla) was found only in three bee-hunting species and for first time in the genus Cerceris. Certain morphological features confirmed the separation of the apoid wasps from the rest of the Apoidea (i.e., bees). A cluster analysis based on the sizes of the different types of sensilla suggested that, overall, sensilla morphology is not a useful taxonomic tool, and thus, other factors likely determine interspecific variability. One candidate factor is the prey type, given some differences in the presence, density, size and distribution of certain types of olfactory sensilla between beetle-hunters and bee-hunters. This hypothesis needs to be further tested quantitatively using a larger species set, more individuals per species, additional sensilla features, and a correction for phylogeny.     

Ultrastructure of antennal sense organs of small ermine moths,Yponomeuta spp. (Lepidoptera : Yponomeutidae)

The ultrastructure of antennal sensilla was investigated in males and females of 5 European Yponomeuta species. Three types of olfactory sensilla could be distinguished, i.e. sensilla trichodea, sensilla basiconica, and sensilla coeloconica. Sexual dimorphism in the number of cells innervating sensilla trichodea could be established in 3 species. Most of these sensilla in males of Y. vigintipunctatus, Y. rorellus, and Y. cagnagellus are associated with 3 sensory cells, whereas in females of these species these sensilla contain 2 sensory cells. In both males and females of Y. padeltus and Y. malinellus, the great majority of the sensilla trichodea is innervated by 3 cells. So-called sensilla chaetica type 1 show features typical of a combined mechano/contact-chemoreceptor. No structures indicating a sensory function were found in sensilla chaetica type 11. Sensilla styloconica contain 3 cells, the dendritic outer segment of one being lamellated; most likely, these cells have a thermo- and hygroreceptive function. The findings concerning the olfactory sensilla are discussed in the context of olfactory communication and reproductive isolation in European Yponomeuta.     

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.     

全球锹甲的几何形态学数据集

几何形态学是通过定量分析手段对生物的形态特征在几何空间中的变化进行测量, 并将这些测量得到的信息转变为数字信息进行统计学分析以达到形态特征间比较的目的, 目前被越来越多地用于探索生物的特征进化和多样性研究。先前的研究通常提取、比对生物的间断性特征信息用以类群之间的划分, 针对连续性特征研究的缺乏使得有关生物进化和形态学的相关知识变得匮乏。锹甲(鞘翅目: 锹甲科)由于其性二型、雄虫多型性和独特的习性成为形态学研究的重要类群。基于此, 本研究中我们提供了一个包含1,302种锹甲成虫(涵盖全世界99%已知种)的形态学数据集, 数据集包含锹甲的典型的连续性特征, 即前胸背板和鞘翅的外轮廓形态。我们提供的数据集为甲虫的生物多样性、系统发育和进化生物学在内的多个学科的研究提供基础。     

Ultrastructure and Comparative Morphology of Mouth-part Sensilla in Ground Beetle Larvae (Insecta, Coleoptera, Carabidae)

Labial and maxillary palps in 22 species of ground beetle larvae revealed the presence of four different types of sensilla: sensilla digitiformia, sensilla campaniformia, sensilla basiconica and sensilla chaetica. Using transmission electron microscopy techniques, the role of most of them was defined: sensilla campaniformia and sensilla chaetica are mechanoreceptors; while sensilla basiconica are chemoreceptors. Sensilla digitiformia can be both mechanoreceptors and chemoreceptors, though hygroreception may also be postulated on the basis of their abundance on the mouthparts of some hygrophilous species that depend on damp or wet patchy biotopes/seasons. The number and location of the sensory structures has been found to vary among the investigated taxa. The differences are related to the larval behavioural types, and are an adaptive response to different lifestyles, feeding habits and use of space.     

Role of galeal sensilla in host recognition and feeding behaviour of the Colorado potato beetle

Abstract. Close-range interactions with plants and the early stages of feeding behaviour of adult Colorado potato beetles, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), were studied using beetles with and without various mouthpart sensilla. Representative host, potato (Solarium tuberosum) , and non-host, tomato (Lycopersicon esculentum) , leaves were treated very differently by beetles with and without their galeal or palpal sensilla. Galeal sensilla were particularly important for beetles interacting with these two plants. Compared with normal beetles, fewer beetles without galeae fed on potato leaves, and those that did feed spent more time assessing the plant and took more bites before feeding. On tomtato, more beetles without galeae fed, spent less time assessing the plant and took fewer bites before feeding. Beetles without galeae also had lower consumption rates on potato and higher consumption rates on tomato. Beetles were very reluctant to feed on tomato if the galeae were present so removal of maxillary sensilla was studied only on potato. Without the sensilla on the maxillary palpi only the time between first touch and first bite was affected (lengthened). The importance of galeal sensilla in host recognition by this species and the implications for chemosensory studies are discussed here and in a companion paper.     

雄蚤生殖节的扫描电镜观察

本文利用扫描电镜对雄蚤生殖节表面细微结构进行了观察,发现了一些光镜下不易看到的纹理状结构和小棘及一些感器.这些微小的纹理状结构和小棘在不同蚤种之间有差异,这种差异具有相对的稳定性,可望用于蚤的亚显微水平的分类.通过对感器的观察,发现生殖节上具有大量的毛形感器,另外还观察到有锥形感器、短锥形感器、钟形感器、栓锥感器、腔锥感器及刺形感器等.这些感器的数量分布及有无因种而异.这些感器的存在与交配行为密切相关,作者对此也进行了讨论.     

异色瓢虫与隐斑瓢虫的区别及其色斑型和横脊的频率

异色瓢虫Harmonia axyridis(Pallas)和隐斑瓢虫H.yedoensis(Takizawa)是亲缘关系很近的姐妹种,在中国(北京到南岭,西至甘肃南部和西藏东部)、日本(北海道以南)和南韩等地同域分布,常常在松树等植物上共存。长期以来,隐斑瓢虫被认为是异色瓢虫的一个异名。有时从外形上很难区分这2种瓢虫,因此对于依据野外数据,分析异色瓢虫色斑型和鞘翅横脊的发生频率及小进化会产生一些错误。本文从没有隐斑瓢虫分布的东北地区的材料及其他数据,报道异色瓢虫的色斑型及鞘翅横脊发生频率。异色瓢虫的花斑型在我国东部地区(从东北至广东北部,西至甘肃和云南)发生率很低,而在新疆西北部发生率较高。鞘翅横脊的发生率从东北佳木斯的98.85%降低到云南大理的78.26%。本文列出了区分这2种瓢虫的形态特征及自然分布。如果鞘翅具横脊,则属于异色瓢虫,但如果标本来自2种瓢虫的共存区,鞘翅没有横脊,鞘翅的斑纹呈花斑型、四窗型或二窗型,则很难从外部形态上对它们进行鉴定。但这2种瓢虫的幼虫很容易区分。本文还提供了2种瓢虫的雄性外生殖器形态图、幼虫和成虫。     

Comparative study of the sensory system in gamasid mites Rhinonyssus rhinolethrum,Rh. subrhinolethrum and Ptilonyssus motacillae (Mesostigmata: Gamasina: Rhinonyssidae), parasites in the nasal cavity of birds

Sensillae of the tarsal receptor complex, palpal organ, and body chaetom were examined by means of scanning electron microscopy in three endoparasitic gamasid mites: Rhinonyssus rhinolethrum, Rh. subrhinolethrum and Ptilonyssus motacillae, the parasites of Anser albifrons, Anas crecca, and Motacilla alba, respectively. In the tarsal sensory complex, the scale of reduction of the olfactory sensilla reflects the adaptation of gamasid mites to cavernous parasitism. The topography of this sensilla is specific at generic and species taxonomic levels. In the palpal sensory organ, the number and scale of reduction of two main sensilla types depend on peculiarities of places of blood-sucking.     

Fine Structure of Elytral Punctures and Diffraction Gratings in Korean Sericinae (Coleoptera, Melolonthidae)

ABSTRACT The surface structures of the elytra in twenty two species belonging to the subfamily Sericinae (Coleoptera, Melolonthidae) were observed by scanning electron microscopy. For viewing specific characters, elytral punctures and diffraction gratings on interstitial surface were focused on. The elytral punctures of observed Sericid beetles have three representative forms: horseshoe, ocellus, and crease types. The diffraction gratings of the elytra show three distinctive patterns: regular and parallel, discontinued, and interconnected and curved. These patterns of elytral punctures and diffraction gratings considered to be useful for identification.