Pump out the volume—The effect of tracheal and subelytral pressure pulses on convective gas exchange in a dung beetle, Circellium bacchus (Fabricus)

Many flightless beetles like the large apterous dung beetle Circellium bacchus, possess a subelytral cavity (SEC) providing an extra air space below the elytra which connects to the tracheal system (TS) via metathoracic and abdominal spiracles. By measuring subelytral and intratracheal pressure as well as body movements and gas exchange simultaneously in a flow-through setup, we investigated the contribution of convection on Circellium respiratory gas exchange.No constriction phase was observed. TS and SEC pressures were always around atmospheric values. During interburst phase open abdominal spiracles and a leaky SEC led to small CO₂-peaks on a continuous CO₂ baseline, driven by intermittent positive tracheal pressure peaks in anti-phase with small negative subelytral pressure peaks caused by dorso-ventral tergite action.Spiracle opening was accompanied by two types of body movements. Higher frequency telescoping body movements at the beginning of opening resulted in high amplitude SEC and TS pressure peaks. High frequency tergite movements caused subelytral pressure peaks and led to a saw tooth like CO₂ release pattern in a burst. We propose that during the burst open mesothoracic spiracles increase the compliance of the subelytral cavity allowing big volumes of tracheal air being pulled out by convection.     

Mobility and microhabitat utilization in a flightless wetland grasshopper, Chorthippus montanus (Charpentier, 1825)

Wetlands are among the most threatened habitat types on our planet. Their decline will probably even intensify under climate change. Many biota are strongly dependent on wetlands, including a large number of invertebrate species. The populations of such hygrophilous species become increasingly disconnected due to the ongoing fragmentation of their habitats. This is particularly true for species with reduced dispersal capacities, such as flightless insects. We studied mobility, population size and microhabitat utilization in a population of an endangered grasshopper species, the Water-meadow Grasshopper, Chorthippus montanus. Our mark-recapture study revealed that the cumulative movement distance of the adults was on average 23.5?m with a maximum of 104?m. The microhabitat analysis showed that both sexes of C. montanus preferred warmer patches with greater radiation than measured at control sites. Niche overlap among sexes was stronger than expected by chance, while niche overlap between insects and controls showed the opposite pattern. Our results suggest that C. montanus is strongly restricted to its habitat and is probably not able to cross larger distances through unsuitable vegetation. Hence, we assume that the populations of this flightless insect species are strongly isolated. However, the effect of the rare macropterous morph of C. montanus on gene flow remains unknown. Wetland restoration is crucial to reconnect the existing wetland patches in Central Europe and thereby reduce the negative effects of habitat fragmentation on wetland species.     

Frictional surfaces of the elytra-to-body arresting mechanism in tenebrionid beetles (Coleoptera : Tenebrionidae) : design of co-opted fields of microtrichia and cuticle ultrastructure

In beetles, the system responsible for an attachment of forewings (elytra) to the thorax consists of interlocking fields of microtrichia (MT) located between thorax and body and between left and right elytra. The present study provides comparative data about microtrichia design on the thorax and elytra in three species of tenebrionid beetles (Tribolium castaneum, Tenebrio molitor, Zophobas rugipes) (Coleoptera : Tenebrionidae), which are different in their size. The length, width, density and directionality of microtrichia in 13 MT fields (4 on the thorax, 1 on the abdomen, 7 on the elytra, and 1 on the costal vein of the hindwing) were quantified. (1) Parameters studied are dependent on the dimension of an insect. The length of the microtrichia of most fields compared increases with an increase in body size. The MT width in the majority of fields increases with an increase in the elytra length. The MT density decreases with an increase in the elytra length. (2) Both width and length of microtrichia increase with an increase in the distance between single MT. The density of outgrowths increases with an increase in their length and width. (3) The fields oriented along the same spatial axis constitute functional groups responsible for a particular direction. Co-opted fields can be oriented in the same or opposite directions. (4) The design of MT correlates in co-opted surfaces. There are 3 field groups, which were stated as functionally corresponding to one another : the medial, anterio-lateral, and posterio-lateral. The lengths and widths of microtrichia from fields of these functional groups were quite similar in corresponding fields. Length-to-width ratios of MT in elytral fields were usually weakly correlated with those of thoracic fields. The distances between microtrichia on the elytra surface directly depended on those of the thorax. Distance-to-width ratio of MT of one surface slightly increased with an increase in this parameter on the co-opted surface. The MT densities on co-opted fields were usually quite different. (5) The ultrastructure of the cuticle suggests differences in the material properties of the cuticle between MT fields. The thoracic fields usually consist of elastic cuticle, whereas elytral fields are much harder. Usually, a MT field of elastic cuticle corresponds to the field composed of hard cuticles. The study also provides information about the ultrastructure of epidermal cells and about the design of pore channels, which are presumably responsible for production and transport of an adhesive secretion into the area of contact between lateral fields. Sensory organs monitoring contact between co-opted binding sites were also studied. The results of this study may aid in understanding the morphological basis of cuticular microsculptures acting as frictional devices.     

Breathe softly, beetle: continuous gas exchange, water loss and the role of the subelytral space in the tenebrionid beetle, Eleodes obscura

Flightless, diurnal tenebrionid beetles are commonly found in deserts. They possess a curious morphological adaptation, the subelytral cavity (an air space beneath the fused elytra) the function of which is not completely understood. In the tenebrionid beetle Eleodes obscura, we measured abdominal movements within the subelytral cavity, and the activity of the pygidial cleft (which seals or unseals the subelytral cavity), simultaneously with total CO2 release rate and water loss rate. First, we found that E. obscura has the lowest cuticular permeability measured in flow-through respirometry in an insect (0.90 microg H2O cm(-2) Torr(-1) h(-1)). Second, it does not exhibit a discontinuous gas exchange cycle. Third, we describe the temporal coupling between gas exchange, water loss, subelytral space volume, and the capacity of the subelytral space to exchange gases with its surroundings as indicated by pygidial cleft state. Fourth, we suggest possible mechanisms that may reduce respiratory water loss rates in E. obscura. Finally, we suggest that E. obscura cannot exchange respiratory gases discontinuously because of a morphological constraint (small tracheal or spiracular conductance). This "conductance constraint hypothesis" may help to explain the otherwise puzzling phylogenetic patterns of continuous vs. discontinuous gas exchange observed in tracheate arthropods.     

Review Phoresy by Hemisarcoptes (Acari: Hemisarcoptidae) on Chilocorus (Coleoptera: Coccinellidae): influence of subelytral ultrastructure

The non-phoretic stages of mites of the genus Hemisarcoptes are predators of the family Diaspididae. The heteromorphic deutonymph (hypopus) maintains a stenoxenic relationship with beetles of the genus Chilocorus. The mites attach to the subelytral surface of the beetle elytron during transport. There is variation in mite density among species of Chilocorus. Both Hemisarcoptes and Chilocorus have been applied to biological control programmes around the world. The objective of this study was to determine whether subelytral ultrastructure (spine density) plays a role in the evolution of symbiosis between the mite and the beetle. The subelytral surfaces of 19 species of Chilocorus and 16 species of Exochomus were examined. Spine density was determined for five subelytral zones: the anterior pronotal margin, medial central region, caudoventral tip, lateral distal margin and epipleural region. Spine density on the subelytral surface of Chilocorus and Exochomus was inversely correlated with the size of the elytron for all zones except the caudoventral tip. This suggests that an increase in body size resulted in a redistribution of spines and not an addition of spines. The pattern of spine density in Exochomus and Chilocorus follows a single size–density trajectory. The pattern of subelytral ultrastructure is not strictly consistent with either beetle phylogeny or beetle allometry. The absence of spines is not correlated with either beetle genus or size and species of either Chilocorus or Exochomus may be devoid of spines in any zone, irrespective of body size. A general difference between species of Chilocorus and Exochomus is the fact that while spine density in Chilocorus is clinal relative to the size gradient, Exochomus is dichotomous and likely to have either many spines or no spines in a particular zone. No species of Chilocorus was completely devoid of spines. Five species of Exochomus had no spines at all, thus making it difficult to interpret the primary function of the subelytral spines in a general way. Within the genus Chilocorus, spine density may play a synergistic role in host association. Based on morphological evidence alone, these findings lead to the hypothesis that the species of Chilocorus that would be most conducive to biological control application in conjunction with Hemisarcoptes would be Chilocorus cacti, Chilocorus distigma, Chilocorus fraternus, Chilocorus orbus, Chilocorus tristis and, to a lesser extent, Chilocorus bipustulatus. © Rapid Science Ltd. 1998     

Dry under water: Comparative morphology and functional aspects of air‐retaining insect surfaces

Superhydrophobic surfaces prevent certain body parts of semiaquatic and aquatic insects from getting wet while submerged in water. The air layer on these surfaces can serve the insects as a physical gill. Using scanning electron microscopy, we investigated the morphology of air‐retaining surfaces in five insect species with different levels of adaptation to aquatic habitats. We found surfaces with either large and sparse hairs (setae), small and dense hairs (microtrichia), or hierarchically structured surfaces with both types of hairs. The structural parameters and air‐film persistence of these surfaces were compared. Air‐film persistence varied between 2 days in the beetle Galerucella nymphaea possessing only sparse setae and more than 120 days in the bugs Notonecta glauca and Ilyocoris cimicoides possessing dense microtrichia (up to 6.6 × 10⁶ microtrichia per millimeter square). From our results, we conclude that the density of the surface structures is the most important factor that affects the persistence of air films. Combinations of setae and microtrichia are not decisive for the overall persistence of the air film but might provide a thick air store for a short time and a thin but mechanically more stable air film for a long time. Thus, we assume that a dense cover of microtrichia acts as a “backup system” preventing wetting of the body surface in case the air–water interface is pressed toward the surface. Our findings might be beneficial for the development of biomimetic surfaces for long‐term air retention and drag reduction under water. In addition, the biological functions of the different air retention capabilities are discussed. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc.     

A preliminary survey of ultraviolet reflectance in beetles

Ultraviolet reflectance is a widely distributed phenomenon among certain families of Coleoptera. It is so far found to occur in Carabidae, Scarabaeidae, Buprestidae, Elateridae, Tenebrionidae, Cerambycidae, Anthribidae and Curculionidae. Of more than 100 species examined, 70 were found to possess UV reflectant structures. Reflection is almost always from pigments contained within microtrichia or other setae. In some Tenebrionidae and Buprestidae, dried secretions forming patches or stripes on the pronota and elytra are reflective and, in a few desert-living Tenebrionidae, reflectance is from subcuticular pigment in the elytra.     

Natural flightless morphs of the ladybird beetle Adalia bipunctata improve biological control of aphids on single plants

The challenge of using ladybird beetles for biological control of insect pests such as aphids is that the adult beetles tend to fly away from the host plants. Therefore, flightless ladybirds might improve biocontrol. There are several artificial ways to obtain flightless beetles, but it may be preferable to use natural variation in flight ability. We investigated, for the first time, biocontrol by inundative augmentation of natural flightless morphs of the ladybird beetle Adalia bipunctata. Microcosm experiments using single leaves with one of three species of aphid revealed no differences in consumption behavior between flightless and winged beetles. Monitoring for 48 h of single, caged pepper plants infested with aphids of Myzus persicae nicotianae or Aulacorthum solani showed that flightless beetles had a longer residence time on the plants than winged beetles. This only translated into significantly better biocontrol of M. persicae. Despite their difference in residence time, both beetle morphs reduced the population growth of A. solani. This is probably explained by the tendency of A. solani to drop from the plant upon disturbance, and we predict that flightless beetles may outperform winged ones in the long term. Overall, our results provide a proof of principle that natural flightless A. bipunctata can improve biocontrol of aphids by ladybird beetles. However, we recognize that the effect of biocontrol will vary with the species of aphid used and that further examination in long term and large scale experiments is required.     

Descriptions of the first semi-aphenopsian troglobiotic Patrobini and of a new anophthalmic cave-dwelling Trechini from central Sichuan,China (Coleoptera: Caraboidea)

Summary

The first known troglobiotic species belonging to the ground beetle tribe Patrobini is reported from a limestone cave called Lianhua Dong in Pengzhou, a suburb county-level city in northern Chengdu, Sichuan Province, China. Troglopatrobus zhouchaoi n. gen., n. sp., is an eyeless and large-sized patrobine beetle with extremely elongated body (esp. head and elytra) and appendages. Duvalioblemus (Shublemus) liyuani n. subgen., n. sp., a minute anophthalmic trechine species, is also discovered from the same cave. It is the first cave-dwelling species belonging to this genus already known as endogean from Sichuan and Yunnan provinces.     

臭蜣螂体壁的组织结构

对臭蜣螂Copris ochus Motschulsky体壁的组织学结构进行了光镜观察。用伊红和马洛赖氏三色法染色可见体壁尤其在腹壁的折叠处及膜翅壁中存在着胶原纤维。鞘翅中有内腔,具皮细胞,鞘翅背部表皮下陷形成桥墩状结构以支撑加固鞘翅腔并减轻重量。膜翅的背腹壁之间也具有内腔和皮细胞,并充满油脂腺（经分析是棕脂肪细胞腺）及其分泌物。足的肌肉束中被大量棕脂肪细胞腺环绕。棕脂肪细胞的存在为周围器官提供所需能量,并有减轻重量和润滑的作用。体壁表面具有大量突起、刚毛及大量粗细不等的管道与其下相通,加上大量油脂腺及其分泌机能,为其体表的减粘特性提供了形态和化学基础。鞘翅内腔的结构可为建筑仿生学提供一定参考。     

The invasion of the carnivorous carabid beetle Trechisibus antarcticus on South Georgia (sub-Antarctic) and its effect on the endemic herbivorous beetle Hydromedion spasutum

Recently two species of carabid beetle were accidentally introduced onto the sub-Antarctic island of South Georgia. Both species are carnivorous and flightless. One of the species, Trechisibus antarcticus, is locally very abundant and in the process of invading the coastal lowland area, where the endemic herbivorous beetle Hydromedion sparsutum (Perimylopidae) is common. Field samples showed the abundance of the endemic species to be much lower, and its adult body size to be larger, in carabid-infested locations than in carabid-free locations. The sample data allowed us to estimate the growth rate of the H. sparsutum larvae and to reconstruct the most likely life-cycle of both species. A laboratory experiment showed a high mortality for the first three (out of six) larval instars of H. sparsutum in groups which had been subjected to predation by T. antarcticus. The duration of the period during which the larvae are vulnerable to predation was shown in a growth experiment to depend on food type. Quantitative and qualitative aspects of the interaction between the introduced predator and the endemic prey, and conditions which allowed the former to invade are discussed.     

Nematodes associated with Ips cembrae (Coleoptera: Curculionidae): comparison of generations,sexes and sampling methods

A study of nematodes associated with the large larch bark beetle Ips cembrae (Heer 1836) was carried out at three locations in the Czech Republic. The proportion of beetles infested by endoparasitic nematodes (representatives of genera Contortylenchus, Parasitylenchus, Cryptaphelenchus and Parasitorhabditis) ranged from 29.9 to 50.9%. Significant differences were determined in nematode infestation levels among locations, generations and sampling methods. No differences were found in infestation rates between males and females. The percentage of bark beetles with phoretic nematodes ranged from 18 to 42.9%. Phoretic nematodes directly found under elytra, on wings and between body segments of the bark beetles belong to the genus Micoletzkya. However, adults and juveniles of other two phoretic species Laimaphelenchus penardi and Bursaphelenchus sp. were found in the gallery frass of I. cembrae. Infestation by phoretic nematodes positively correlated with the presence of mites under elytra.     

The Larval Stage and Life Cycle of Diplodontus scapularis Dugès, 1834, and D. semiperforatus Walter, 1925 (Acari: Hydrachnidia), with Remarks on Their Habitat Preference and Distribution in the South West Palaearctic Region

The larva of D. scapularis Dugès, 1834, is redescribed from material collected in Morocco, and a comparison is made with larvae of the closely related D. semiperforatus (Walter, 1925) reared in the laboratory. Larvae of D. scapularis were found parasitic in the subelytral space of several beetle species of the families Hydraenidae, Hydrochidae and Hydrophilidae. New records are given of Diplodontus scapularis from Morocco and of D. semiperforatus from Spain. The two species differ in salinity tolerance, with D. semiperforatus obviously adapted to saline and hypersaline inland waters.     

Ultrastructure of the thoracic dorso‐medial field (TDM) in the elytra‐to‐body arresting mechanism in Tenebrionid Beetles (Coleoptera: Tenebrionidae)

Beetles with flying ability lock their elytra (forewings) to the thorax or/and abdomen using complex locking devices. These structures are often supplemented with microtrichia fields of the inner surface of the elytra and adjacent parts of the pterothorax. The present study provides information about the ultrastructure of microtrichia of the dorso‐medial fields of the thorax (TDM) in tenebrionid beetles (Tribolium castaneum, Zophobas rugipes). Epidermal cells located under the TDM field contain large electron‐lucent vesicles connected to rough endoplasmic reticulum. Microtrichia and underlying cuticle of the TDM have a high density of pore channels, which are responsible for transport of an epidermal secretion onto the TDM surface. In order to show the presence of the secretion on the cuticle surface, TDM fields of air‐dried specimens were compared with those in specimens after two treatments, such as (1) dehydration in ethanol and acetone, and (2) dental‐wax‐cast technique applied to living beetles. This revealed the presence of the nonvolatile film on the intact microtrichial surface. Possible functions of this film are suggested to be (1) the increase of adhesive forces in the contact area and (2) providing soft coupling and release of two corresponding parts of the elytra‐locking device. J. Morphol. 240:101–113, 1999. © 1999 Wiley‐Liss, Inc.     

The evolution of Batesian mimicry within the North American Asidini (Coleoptera: Tenebrionidae)

The asidine darkling beetles (Coleoptera: Tenebrionidae: Asidini) are a diverse tribe of flightless tenebrionids found in many arid and sub‐arid habitats around the world. The 263 currently described North American species are contained in ten genera, all of which are restricted to the western half of the continent. The Asidini, like all members of the subfamily Pimeliinae, lack defensive glands. Instead, several phenotypic traits occur within the tribe that may help limit predation. These include the contrasting defensive strategies of crypsis, through either background matching or pattern disruption, and Batesian mimicry of the chemically defended genus Eleodes. Dorsal elytral morphology was assessed between 53 North American asidine species and 13 common Eleodes model species using multiple methodologies to assess similarities between species in the two groups that might indicate mimetic relationships. A phylogeny of the North American asidines is used to map the occurrence of differing defensive strategies within the tribe. Crypsis is reconstructed as the ancestral state, with two origins for Batesian mimicry and multiple reversals. The combination of strongly to weakly cryptic species and varying levels of mimetic fidelity to Eleodes model species make the asidines a promising lineage upon which to further explore the evolution of defensive phenotypes.     

Attachment site and infestation parameters of parasitic water mites on the whirligig beetle Dineutus nigrior Roberts (Coleoptera: Gyrinidae)

Larval water mites parasitise a wide range of aquatic insects and may have a negative impact on host fitness. One host taxon susceptible to water mite parasitism is the whirligig beetle (Coleoptera: Gyrinidae). We made 11 collections of the whirligig beetle Dineutus nigrior Roberts from May to October of 2006 to investigate patterns of water mite parasitism on that host species. Mites were identified as of the genus Eylais. Mite intensity ranged from 1 to 11. Median intensity was 1.0 and ranged from 1.0 to 3.0 for individual samples. There did not appear to be temporal patterns in mite intensity. Prevalence was 30.9% but varied substantially over the sampling period ranging from 2.5 to 63.3%. Mites were attached to the metathoracic wings and the body tergites under the elytra. When all samples were considered there was equal use of wings and body tergites but there was temporal variation in the use of attachment sites.     

Threats to monsoon rainforest habitat in northern Australia: The case of Ptychosperma bleeseri Burret (Arecaceae)

Abstract Rainforest patches in the Australian wet-dry tropics occur as habitat islands. Recent studies show that many patches are severely damaged by feral animals, weed invasion and contemporary fire regimes. This paper documents the status of an endangered palm species, Ptychosperma bleeseri, which occurs within a narrow geographical range in seven rainforest patches. Results of multivariate statistical analysis of quadrats with and without P. bleeseri show that the species does not appear to occupy all suitable habitat available at either a regional scale or within single rainforest patches. Evidence, based on demographic surveys, is presented for the current decline of P. bleeseri populations and possible causes for this decline are discussed; in particular, the impacts of wildfire and feral animal activity. Recommendations for a recovery plan for P. bleeseri are discussed, and include fencing, fire protection and public education.     

塔克拉玛干沙漠北缘柽柳灌丛沙堆对甲虫的庇护作用

以塔克拉玛干沙漠北缘典型荒漠区柽柳灌丛沙堆-柽柳包为研究对象,在2005—2006年期间调查了柽柳包及相邻沙漠裸地地表甲虫多样性。结果表明:2005年和2006年柳包上地表甲虫个体数量和物种数均高于沙漠裸地,柽柳包上的地表甲虫物种数分别为21种和16种,沙漠裸地中分别为10种和12种,柽柳包上物种丰富度明显高于沙漠裸地。选取优势种髋胫小土甲(Penthicicus koltzei Reitter)进行相对种群密度的估算,髋胫小土甲在柽柳包上分布数量较多,密度可达到每平方米在13头以上;但沙漠裸地仅有6头左右。柽柳包对甲虫多样性有明显的庇护所的作用,有利于维持甲虫物种多样性。2种不同生境条件下地表甲虫的数量存在明显的季节变动,其数量高峰分别出现在2005年6月和2006年7月,可能与不同季节环境的极端性(如气温峰值和洪水早晚)导致的食物丰富程度有关。     

Beetle species’ responses suggest that microclimate mediates fragmentation effects in tropical Australian rainforest

Abstract Despite the enormous contribution of invertebrates to global biodiversity and ecosystem function, the patterns and causes of insect responses to tropical rainforest destruction and fragmentation remain poorly understood. We studied the responses of beetles to these factors in a fragmented upland rainforest landscape in north‐east Queensland, Australia. Beetles were sampled using flight interception traps from six replicate sites in rainforest interior, rainforest edge, small rainforest remnants and pasture, interspersed across about 600 km². Beetles from 10 family/subfamily groups were sorted to species. There were three major findings. First, converting rainforest into pasture has a very strong negative effect on beetle diversity and species composition. Very few beetle species were present in pasture and none of the most abundant species was more abundant in pasture than rainforest. Second, beetle assemblages appeared to respond to climate. Beetle species composition in drier rainforest habitats was different from that of moister rainforest and there were species unique to each rainforest type. Third, beetle species composition differed between small remnants and interior rainforest: drier‐associated species were more abundant in small remnants, whereas wetter‐associated species were more abundant in interiors. Edges tended to be intermediate. We argue that this pattern can be attributed to a fragmentation effect mediated by differences in microclimate rather than by floristic, structural, or area and isolation effects.     

Specialization of rainforest canopy beetles to host trees and microhabitats: not all specialists are leaf‐feeding herbivores

Reliable estimates of host specificity in tropical rainforest beetles are central for an understanding of food web dynamics and biodiversity patterns. However, it is widely assumed that herbivores constitute the majority of host specific species, and that most herbivore species feed on leaves. We tested the generality of this assumption by comparing both plant host‐ and microhabitat‐specificity between beetle communities inhabiting the foliage (flush and mature), flowers, fruit, and suspended dead wood from 23 canopy plant species in a tropical rainforest in north Queensland, Australia. Independent of host tree identity, 76/77 of the most abundant beetle species (N ≥ 12 individuals) were aggregated on a particular microhabitat. Microhabitat specialization (measured by S_m and Lloyd's indices) was very high and did not differ between flower and foliage communities, suggesting that each newly‐sampled microhabitat has a large additive effect on total species richness. In accordance with previous studies, host specificity of foliage‐inhabiting beetles was most pronounced among herbivorous families (Curculionidae, Chrysomelidae). By contrast, host specificity among flower‐visitors was equally high among herbivorous and nonherbivorous families (e.g. Nitidulidae, Staphylinidae, Cleridae). Effective specialization (F_T) measures showed that traditional correction factors used to project total species richness in nonherbivorous groups fail to fully capture diversity in the flower‐visiting beetle fauna. These results demonstrate that host specialization is not concentrated within folivores as previously assumed. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 215–228.