Tracheole migration in an insect wing

Summary Insect tissues are supplied with oxygen by a system of long and highly branched cuticular tubes known as tracheae and tracheoles. During the growth of with imaginal discs in moths and butterflies, tracheole cells migrate distally from the base of the disc. Tracheoles radiate in a distal direction through the extracellular space sandwiched between the upper and lower epithelial surfaces of the wing.Migration of most cells is assumed to be governed by forces intrinsic to the cell. However, the movement of tracheoles is apparently a passive process whose motive force resides in adjacent epithelial cells. After epithelial cells are exposed to ecdysteroid hormones, these cells extend basal processes that are attracted to oxygen-rich tracheoles. By applying traction to the tracheoles with which they establish intimate contact, epithelial cells may control the pattern of their distribution within wing tissue.     

昆虫数字化博物馆的建设

数字化博物馆是博物馆现代化的一个重要标志。国外博物馆从20世纪90年代就开始进行数字化建设,国内的博物馆数字化建设起步较晚,同国外的先进技术相比还有一定的差距,但发展较快。目前,国内外已有的昆虫数字化博物馆各具特色,有以展示昆虫图片为主的,有以介绍昆虫知识为主的,也有以营利为目的的,但仍有不少需要改进的地方。为了满足中小学生的求知欲和探索欲,适应他们喜欢自己动手操作和活泼好动的性格,昆虫数字化博物馆网站建设在技术上应采用J2EE三层体系结构,采用动态网站内容管理与发布系统构建的后台管理系统,将昆虫数字化博物馆分成后台管理和前台展示与交互两部分,从而实现网站内容与表现形式的分离,加快网页更新的速度。在数据库建设上,应采用功能强大的数据库软件,以满足大量图片、声音、动画、视频等多种类型的数据库的有效存储和高效的检索功能。在网站的内容上应有实体展厅的数字化、昆虫学术交流与知识集锦、中小学生互动教育等板块。在网站的后期维护上应做到由全社会的昆虫爱好者共同维护和管理。     

Paramyosin content and thick filament structure in insect muscles

Summary The myosin filaments of the flight muscles of the locust Locusta migratoria, the cockchafer Melolontha melolontha and the femur muscles of L. migratoria have solid centers. Those of the flight muscles of the housefly Musca domestica and Drosophila melanogaster are tubular. Electron micrographs of myofibrils of the fleshfly Phormia terrae-novae contain both filament types within one sarcomere and suggest the existence of 4 cross-bridges per crown.Estimates of the ratios of myosin to paramyosin and of myosin to actin on sodium dodecyl sulphate-polyacrylamide gels yielded paramyosin contents of 9% of the thick filament mass for the solid and 2.6% for the tubular filaments (3.8% for P. terrae-novae). Based on the myosinactin ratios up to 6 myosin dimers per crown could be calculated.The molar ratio of actin to arthrin on SDS gels was found to be 3.37 for native and extracted myofibrils of flight muscles from P. terrae-novae. Arthrin is also present in isolated actin filaments suggesting that it is localized in or on the thin filaments. If we assume that it is constituent part of the helices of the thin filaments the number of myosin dimers per crown can be diminished to 4.5, considerably closer to the values obtained by evaluation of electron micrographs.Dedicated to Prof. Dr. Bernhard Rensch on his 85^th birthday     

Hysteresis of insect acetylcholinesterase

Pre-steady-state catalytic properties of insect acetylcholinesterase (AChE, EC 3.1.1.7) were studied with the neutral substrate N-methylindoxylacetate. Kinetics of soluble Apis mellifera and Drosophila melanogaster AChE forms showed lags (v(i)=0) before reaching the steady-state. Results were interpreted in terms of slow equilibrium between two conformational states E and E' of insect AChE. Hysteresis of insect AChE has been pointed out for the first time. The hysteretic behaviour was found to depend on the NMIA concentration and the nature of the enzyme. The maximum induction times (tau(max)) to reach the steady-state were 800 and 1000s with soluble AChE from A. mellifera and D.melanogaster, respectively. The orders of magnitude of the tau(max) were high and similar to human AChE and BuChE.     

Localization of the pupil trigger in insect superposition eyes

Summary In the superposition eyes of the sphingid moth Deilephila and the neuropteran Ascalaphus, adjustment to different intensities is subserved by longitudinal migrations of screening pigment in specialized pigment cells. Using ophthalmoscopic techniques we have localized the light-sensitive trigger that controls pigment position.In both species, local illumination of a small spot anywhere within the eye glow of a dark-adapted eye evokes local light adaptation in the ommatidia whose facets receive the light. Details of the response pattern demonstrate that a distal light-sensitive trigger is located axially in the ommatidium, just beneath the crystalline cone, and extends with less sensitivity deep into the clear zone. The distal trigger in Deilephila was shown to be predominantly UV sensitive, and a UV-absorbing structure, presumably the distal trigger, was observed near the proximal tip of the crystalline cone.In Ascalaphus we also found another trigger located more proximally, which causes local pigment reaction in the ommatidia whose rhabdoms are illuminated (the centre of the eye glow). The light-sensitive trigger for this response appears to be the rhabdom itself.     

The emergence of verb-particle constructions in Italian: locative and actional meanings

The paper deals with verb-particle constructions in Italian, i.e. complex predicates formed by a verbal base and a modifying post-verbal particle. In recent years a lot of interest has been devoted to these constructions in the Germanic languages, and investigation has been focusing mostly on their structure. Recently, some studies have shown that similar constructions also exist in the Italian language. Our contribution adopts a constructionist approach and aims at improving our knowledge of the properties of verb-particle constructions in Italian with particular reference to semantics and Aktionsart. The paper shows that Italian post-verbal particles contribute to the Aktionsart of verb-particle constructions. Even though Italian does not present a coherent system of actional particles, there are nonetheless some traces of regularity. One case in point is the emergence of a specific verbparticle construction with via ’away’ that developed an actional function. The paper also discusses the diachronic and synchronic relationship between verbal prefixes and post-verbal particles, trying to determine whether these two strategies cooperate or compete in the expression of locative and aspectual meanings. The article is the result of the close collaboration of both authors; however, for academic purposes, Claudio Iacobini is responsible for Sects. 2, 2.1, 2.4, 2.5, 3, 3.1, 3.2 and 5, and Francesca Masini for Sects. 1, 2.2, 2.3, 3.3, 3.4 and 4.     

Effects of livestock grazing on aboveground insect communities in semi-arid grasslands of southeastern Arizona

Despite the importance of invertebrates in grassland ecosystems, few studies have examined how grassland invertebrates have been impacted by disturbances in the southwestern United States. These grasslands may be particularly sensitive to one common disturbance, livestock grazing, because they have not recently evolved in the presence of large herds of bison, an important mammalian herbivore. This study examined how livestock grazing influenced vegetation-associated insect communities in southeastern Arizona. Insect abundance, richness, diversity, community composition, and key environmental variables were compared between sites on active cattle ranches and sites on a 3160 ha sanctuary that has not been grazed by cattle for over 25 years. Vegetation-associated insect communities were found to be sensitive to livestock grazing. Overall abundance of these insects was lower on grazed grasslands, and certain insect orders appeared to be negatively affected by livestock grazing; beetles were less rich, flies were less diverse, and Hymenoptera were less rich and diverse on grazed sites. Conversely, Hemiptera were more diverse on grazed sites. Species composition of vegetation-associated insect communities also differed and was significantly correlated with percent vegetation cover and number of shrubs. Insect species responsible for these differences were taxonomically diverse, and included herbivores and predators/parasites. When compared to other studies conducted in areas of the United States that fall within the historic range of bison, this study suggests that invertebrates in areas outside this range may be more sensitive to grazing pressure.     

Estimation of the stage-specific survival rate in the insect population with overlapping stages

An application ofHokyo andKiritani 's method (1967) was attempted to estimate the stage specific survival rates of the population with overlapping stages. This method can be written as follows assuming a constant daily survival rate (K) throughout the life: where, and F refer respectively to the total incidence of ith instar nymphs and that of individuals after ith instar inclusive, and α_i refers to the developmental period of ith instar. Application of this model to caged and natural populations of the southern green stink bug, Nezara viridula, was made to test its validity. The estimates of the initial number of successive stages obtained from the present method were compared with those fromRichards andWaloff 's method (1954) for the caged populations of 1st, 2nd and 3rd generations. The superiority of the present method to theRichards andWaloff 's in estimating adult numbers was shown in all the generations examined. When different daily survival rates are involved in the course of population decrease, application of the revised method proposed byHokyo andKiritani (1967), gives much reliable estimate as compared with one before correction. The present method is useful in constructing life table of such species as scale insects which complete their life cycle within a defined space, but their successive stages overlap considerably.     

Recurrent and synchronous insect pest outbreaks in forests

A minimal model for the interactions of trees, insects, and their enemies suggests a simple formula for splitting all forests where insect outbreaks can occur into two categories: where outbreaks are periodic and endogenously generated and where outbreaks are triggered by exogenous factors and are, in general, recurrent but aperiodic. The formula is in full agreement with all field studies in which various phenomena triggering insect outbreaks have been identified. The observed consequences of introductions and removals of insects are also well predicted by the minimal model. But, even more surprisingly, the model allows a simple and explicit condition for the synchronization of outbreaks in spatially extended forests to be derived analytically. This condition is, in general, satisfied when the insect is a so-called pest, that is, when the outbreaks are extreme. The model also predicts the possibility of traveling waves of insect outbreaks.     

An insect retina without microvilli in the male scale insect,Eriococcus sp. (Eriococcidae,Homoptera)

Summary Male scale insects of an undescribed Australian species of Eriococcus have no compound eyes but show an extraordinary arrangement of three pairs of ocelli: One pair is positioned dorsolaterally where most insects have their compound eyes. Another pair looks ventrally and is placed where insects usually have their mouthparts, and there are two small lateral ocelli. Corneal nipples and a spherical lens with an estimated F-number only 0.55 are structural adaptations considered to increase the overall light sensitivity in order to compensate for the poor quantum capture of the shallow retina whose rhabdomes are only 3 m long. The outer segment of each receptor cell consists of a central core of cytoplasm containing mitochondria and a peripheral cylinder of about 16 rhabdomeres. There is no optical separation between neighbouring outer segments. Uniquely in arthropod eyes, the light sensitive structures are not composed of cylindrical microvilli, but consist of membrane stacks whose configuration is analogous to the stacked plates of vertebrate cones. At present no conclusive answer can be given as to why the photoreceptors have plates instead of microvilli. Comparative calculations show that they do not contain more photosensitive membrane per unit volume than rhabdomeres of fly ocelli.     

An enigmatic new stick insect from the Philippine Islands (Insecta: Phasmatodea)

A new genus and species of stick insect is described and figured from Mount Halcon, on the Philippine island of Mindoro. Conlephasma enigma gen. et sp. n. is a stout, flightless, and apparently ground-dwelling species with vivid integumental colors. When disturbed, specimens spray a defensive secretion from the prothoracic exocrine glands. The systematic position of Conlephasma within Euphasmatodea is unclear. The elongated galealobulus and the trichome area located laterally in the galea, represent unusual apomorphic characters of the maxilla that could indicate affinities with Necrosciinae or Pseudophasmatinae. All tibiae exhibit the anareolate condition. Euplantulae are of two types: those of tarsomeres I–IV feature a nubby microstructure, whilst the one on the ventral side of the pretarsus is smooth. Males are characterized by the presence of a well-developed vomer on the tenth abdominal segment. A distinctive and apomorphic trait of female terminalia is represented by the elongated tenth abdominal tergum. Conlephasma can represent an interesting taxon for studies on the evolution of the stick and leaf insects.     

QTL analysis of trichome-mediated insect resistance in potato

Genetic mapping of several components of a complex type of insect resistance has been undertaken as a means toward more efficient use of the valuable characteristics of a wild relative of potato. RFLP maps constructed on interspecific diploid progenies of Solanum tuberosum × S. berthaultii were used in conjunction with morphological, biochemical and biological phenotyping to identify quantitative trait loci (QTLs) contributing to trichome-mediated insect resistance. By superimposing QTL data for a wide range of phenotypes including biochemical assays, correlative and direct screens for insect resistance, and adaptation to the target environment on the genetic maps, we have addressed the organization, action and interaction of genes controlling the resistance mechanism. The outcome contributes to an understanding of the association between component traits and between desirable and undesirable features of the donor species generated in an applied breeding program. Research is proceeding toward the development of selectable markers for the introgression and transfer of this resistance among potato gene pools.     

The sexually transmitted insect virus,Hz-2V

Hz-2V is one of only a very few sexually transmitted viruses currently known in insects. Replication of this insect pathogenic virus results in sterility of infected moths rather than mortality. The sterility of the infected host is a consequence of virus directed malformation of adult reproductive tissues, which in females results in cellular proliferation and hypertrophy of these tissues. Virus replication has additional ramifications in infected females. Infected females produce more mating pheromones and attract more mates than healthy females, ultimately facilitating virus transmission and enhancing viral fitness. The molecular mechanisms used by the virus to manipulate the host to enhance its fitness are yet to be determined. Unraveling the underlying principles of these mechanisms promises to enhance our understanding of insect reproductive physiology, as well as provide molecular tools for use in novel approaches in sterile insect control programs.     

"Neuroethoendocrinology": integration of field and laboratory studies in insect neuroendocrinology

Progress in the field of insect neuroendocrinology has been rapid despite the relatively small number of investigators working on insect systems. This progress, in part, reflects the ease of studying insect behavior in the laboratory, and a historical perspective reveals that insect neuroendocrinology has been dominated since its inception by laboratory studies. Recent advances in methodology and a renewed interest in the concept of behavioral state in insects suggest that it might be useful for insect neuroendocrinologists to spend a little more time in the field.     

A micro-CT approach for determination of insect respiratory volume

Variation in the morphology of the insect tracheal system can strongly affect respiratory physiology, with implications for everything from pest control to evolution of insect body size. However, the small size of most insects has made measuring the morphology of their tracheal systems difficult. Historical approaches including light microscopy and scanning and transmission electron microscopy (SEM, TEM) are technically difficult, labor intensive, and can introduce preparation artifacts. More recently, synchrotron X-ray microtomography (SR-μCT) has allowed for detailed analysis of tracheal morphology of diverse insects. However, linear accelerators required for SR-μCT are not readily available, making the approach unavailable for most labs. Recent advancements in microcomputed tomography (μCT) have made possible fine resolution of internal morphology of very small insects. However, μCT has never been used to quantify insect tracheal system dimensions. We measured respiratory volume of a grasshopper (Schistocerca americana) by analysis of high resolution μCT scans. Volume estimates from μCT closely matched volume estimates by water displacement as well as literature estimates for this species. The μCT approach may thus provide a widely available, cost-effective, and straightforward approach to characterizing the internal morphology of insect respiratory systems.     

The spatial distribution of soil hyphae in structured spruce-forest soils

The external mycelium forms the major part of the absorbing surface of mycorrhized tree roots. Because the macro pore space of acid forest soils is selectively depleted of mobile nutrient cations, it is ecologically important, whether soil hyphae grow into the soil aggregates or not. Seedlings of Norway Spruce (Picea abies (L.) Karst.) with defined mycorrhiza were grown in unsterilized soil cores taken from the A and B-horizon of a limed and an unlimed cambisol on triassic sandstone in the Northern Black Forest, Germany. Water-tension treatments were 10, 30, 160 and 900 hPa. On ground and polished vertical cuts stained with acridine orange, we identified and measured the location of hyphae and characterized their micropedological environment using an image analyzing system. Mean length density varied between 17 m/cm³ and 100 m/cm³ and was independent of aeration parameters. The percentage of hyphae completely embedded in the soil matrix varied between 30% and 8% and decreased significantly with increasing CO₂ concentration in the soil air. Of the hyphae in the soil matrix, 70% were located in a 50 m shell around the macro pores. Pair correlation functions show, that the majority of soil hyphae occur in clusters with diameters below 100 m. Between 60% and 80% of randomly chosen circles with 250 m diameters were completely devoid of hyphae. The inefficient opening up of the intra-aggregate space by soil hyphae is explained by the very slow oxygen diffusion between air-filled macro pores and the intra-aggregate space and mechanical restrictions for hyphae growth.     

Enantiospecific synthesis and insect feeding activity of sulfur-containing cyclitols

The first syntheses of two deoxythiocyanocyclitols (4-deoxy-4-thiocyano-l-chiro-inositol and deoxythiocyanoconduritol F) and two deoxysulfonylcyclitol acetals are reported by a chemoenzymatic enantioselective route. The compounds were prepared by a sequence of enzymatic and ruthenium-catalyzed dihydroxylations, and the results were studied regarding reaction conditions and co-catalyst for different derivatives. The new compounds were included in a minilibrary of deoxygenated cyclitols and evaluated for their capacity to influence the feeding behavior of Epilachna paenulata (Coleoptera: Coccinellidae), a common pest of the Curcubitaceae crops.     

Sclerotin and lipid in the waterproofing of the insect cuticle

In all the cuticles studied waterproofing is effected by extracuticular material, a mixture of sclerotin precursors and lipids, exuded from the tubular filaments of the pore canals. In Rhodnius larval abdomen it is a layer of thickness similar to the outer epicuticle, believed to be composed of 'sclerotin' and wax, in Schistocerca larval sternal cuticle and in Carausius sternal cuticle it is similar. In Tenebrio adult sternal cuticle of the abdomen, in both the extracuticular exudation and the contents of the distal endings of the tubular filaments, the wax component is obscured by hard 'sclerotin'. In Manduca larva a very thin layer of 'sclerotin' and wax is covered by an irregular wax layer, average 0.75 micron, twice the thickness of the inner epicuticle. In Periplaneta and Blattella the abdominal cuticle is covered by a soft waxy layer, often about 1 micron thick, which is mixed with argentaffin material. Below this is a very thin waterproof layer of wax and 'sclerotin' continuous with the contents of the tubular filaments, which is readily removed by adsorptive dusts. In Apis adult abdominal terga free wax plus sclerotin precursors form a thin layer which is known to be removed by adsorptive dusts. In Calliphora larva there is a very thin layer of the usual mixed wax and sclerotin and below this a thick (0.5 micron) layer, lipid staining and strongly osmiophil, likewise extracuticular and exuded from the epicuticular channels. This material (which is often called 'outer epicuticle') has the same staining and resistance properties as the true outer epicuticle on which it rests. In the abdomen of Calliphora adult the waterproofing wax-sclerotin mixture forms a thin layer over the entire cuticle including the surface of the microtrichia. There is also a thin detachable layer of free wax on the surface.     

Visual pigment processes and prolonged pupillary responses in insect photoreceptor cells

The visual pigment in the peripheral retinular cells of the hoverfly Syrphus balteatus was investigated by absorbance difference measurements. Different visual pigments were found in the dorsal versus the ventral part of the eye in the male, but not in the female. In the male in the dorsal part of the eye the visual pigment has an isosbestic point at 513 nm; in the ventral part this value is 490 nm. The latter value is found in the female in both parts of the eye.Prolonged pupillary responses were studied in the male Syrphus and appeared to be most marked in the ventral part of the eye. In both hoverfly and blowfly prolonged pupillary responses are induced by short wavelength light only; i.e., by light which excessively can convert rhodopsin into metarhodopsin. By contrast, in butterflies red light (and a long dark adaptation time) is necessary to evoke a prolonged pupillary response. It was demonstrated in both hoverfly and blowfly that long wavelength light, which reconverts metarhodopsin into rhodopsin, inhibits a prolonged pupillary response; or, accelerates pupil opening.Based on material presented at the European Neurosciences Meeting, Florence, September 1978     

A look inside odorant-binding proteins in insect chemoreception

Detection of chemical signals from the environment through olfaction is an indispensable mechanism for maintaining an insect’s life, evoking critical behavioral responses. Among several proteins involved in the olfactory perception process, the odorant binding protein (OBP) has been shown to be essential for a normally functioning olfactory system. This paper discusses the role of OBPs in insect chemoreception. Here, structural aspects, mechanisms of action and binding affinity of such proteins are reviewed, as well as their promising application as molecular targets for the development of new strategies for insect population management and other technological purposes.