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Extracellular matrix (ECM) provides various types of direct interactions with cells and a dynamic environment, which can be remodeled through different assembly/degradation mechanisms to adapt to different biological processes. Herein, through introducing polyphosphate-modified hyaluronic acid and bioactive glass (BG) nano-fibril into a self-assembled hydrogel system with peptide-polymer conjugate, we can realize many new ECM-like functions in a synthetic polymer network. The hydrogel network formation is mediated by coacervation, followed by a gradual transition of peptide structure from α-helix to β-sheet. The ECM-like hydrogels can be degraded through a number of orthogonal mechanisms, including treatments with protease, hyaluronidase, alkaline phosphatase, and calcium ion. As 2D coating, the ECM-like hydrogels can be used to modify the planar surface to promote the adhesion of mesenchymal stromal cells, or to coat the cell surface in a layer-by-layer fashion to shield the interaction with the substrate. As ECM-like hydrogels for 3D cell culture, the system is compatible with injection and cell encapsulation. Upon incorporating fragmented electrospun bioactive glass nano-fibril into the hydrogels, the synergetic effects of soft hydrogel and stiff reinforcement nanofibers on recapitulating ECM functions result in reduced cell circularity in 3D. Finally, by injecting the ECM-like hydrogels into mice, gradual degradations over a time period of one month and high biocompatibility have been shown in vivo. The contribution of complex network dynamics and hierarchical structures to cell-biomatrix interaction can be investigated multi-dimensionally, as many mechanisms are orthogonal to each other and can be regulated individually.

Structures and functions of eukaryotic cells with an outer permeable membrane, motility, a cytoskeleton, biomolecules diffusion, and functional organelles can be imitated by a multi-compartmentalized and large-sized protocell containing various synthetic organelles. Herein, two kinds of artificial organelles with stimuli-trigged regulation ability, glucose oxidase-(GOx)-loaded pH-responsive polymersomes A (GOx-Psomes A) and urease-loaded pH-responsive polymersomes B (Urease-Psomes B) for probing biomimetic pH homeostasis, and a pH-sensor (Dextran-FITC) are encapsulated into proteinosomes by Pickering emulsion method. Thus, the polymersomes-in-proteinosome system is realized. Alternating input-regulation of fuels (glucose or urea) outside the protocell penetrates the membrane of proteinosomes and enters into GOx-Psomes A and Urease-Psomes B to produce chemical\biological signals (gluconic acid or ammonia) resulting in pH-feedback loops (pH jump and pH drop). This will counteract the catalytic “switch on” or “switch off” of enzyme-loaded Psomes A and B owing to their different pH-responsive membranes. Thus, the Dextran-FITC promotes a controlled cytosolic spatial organization and the detection of slight pH fluctuations in the lumen of protocells. Overall, this approach shows heterogeneous polymersome-in-proteinosome architectures with sophisticated features such as induced input-regulated pH changes mediated by negative/positive feedback in loops and cytosolic pH self-monitoring, requirements strictly needed in an advanced protocell design.

A recently developed biopesticide made of safflower and cottonseed oils has excellent ovicidal activity against the hard‐to‐control spider mite Tetranychus urticae Koch (Acari: Tetranychidae). It has attracted attention as a sustainable treatment for controlling T. urticae because it has low potential for promoting resistance and little effect on the predatory mite Neoseiulus californicus (McGregor) (Acari: Phytoseiidae), which is an important natural enemy of spider mites. Here, we investigated the mechanism of its ovicidal activity against T. urticae. The oil droplets in the oil‐in‐water emulsion of the biopesticide strongly adhered to T. urticae eggs, seeped through the chorion being cut during hatching, and inhibited the embryonic rotational movement necessary for cutting and hatching. No adverse effect was observed on N. californicus eggs even in undiluted biopesticide. We conclude that this biopesticide and N. californicus can be used simultaneously in the integrated management of T. urticae in oily biopesticide‐tolerant plant species.

Background and aims Foliar water uptake (FWU) has been documented in many species and is increasingly recognized as a non-trivial factor in plant–water relationships. However, it remains unknown whether FWU is a widespread phenomenon in Pinus species, and how it may relate to needle traits such as the form and structure of stomatal wax plugs. In this contribution, these questions were addressed by studying FWU in current-year and 1-year-old needles of seven Pinus species. Methods We monitored FWU gravimetrically and analysed the needle surface via cryo-scanning electron microscopy. Additionally, we considered the effect of artificial wax erosion by application of the surfactant Triton X-100, which is able to alter wax crystals. Key results The results show for all species that (1) FWU occurred, (2) FWU is higher in old needles compared to young needles and (3) there is substantial erosion of stomatal wax plugs in old needles. FWU was highest in Pinus canariensis, which has a thin stomatal wax plug. Surfactant treatment enhanced FWU. Conclusions The results of this study provide evidence for (1) widespread FWU in Pinus, (2) the influence of stomatal wax plugs on FWU and (3) age-related needle surface erosion.

Omnivorous predatory mirid bugs Dicyphus errans Wolff and closely related species, belonging to the subfamily Bryocorinae (Heteroptera, Miridae), prefer to live on pubescent plant species, where other entomophagous insects are hampered. Previous studies demonstrated a positive relationship between plant trichome diameter and length with attachment forces of D. errans walking on the plant surface. These force data are now pooled with results obtained in life history and feeding assays. Thus, intriguing relationships in mirid bug–plant associations are elucidated. Foothold matters in the highly complex life of omnivorous D. errans. Similar to previously measured traction forces, corresponding safety factors (attachment force/body weight) increase significantly with trichome diameter and length. Fecundity, hatching rate, and juvenile development relate significantly and positively with increased safety factor. Higher safety factors, i.e., stronger attachment on the plant, correspond to a higher consumption rate. The present study confirms a crucial role of insect–plant interactions at the plant surface–insect integument interface. Insect settlement on plants depends on insect attachment ability (i.e., foothold), which is influenced by plant substrates. Hence, the impact of plant surface structures on mirid bug’s, or even wider, on insect attachment ability and interfacial interactions should further be carefully considered when evaluating insect life history, prey consumption, and multitrophic plant–insect associations in the context of evolution, ecology, and sustainable pest management.

Conductive hydrogels (CHs) are emerging as a promising and well-utilized platform for 3D cell culture and tissue engineering to incorporate electron signals as biorelevant physical cues. In conventional covalently crosslinked conductive hydrogels, the network dynamics (e.g., stress relaxation, shear shining, and self-healing) required for complex cellular functions and many biomedical utilities (e.g., injection) cannot be easily realized. In contrast, dynamic conductive hydrogels (DCHs) are fabricated by dynamic and reversible crosslinks. By allowing for the breaking and reforming of the reversible linkages, DCHs can provide dynamic environments for cellular functions while maintaining matrix integrity. These dynamic materials can mimic some properties of native tissues, making them well-suited for several biotechnological and medical applications. An overview of the design, synthesis, and engineering of DCHs is presented in this review, focusing on the different dynamic crosslinking mechanisms of DCHs and their biomedical applications.

Successful host search by parasitic wasps is often mediated by host-associated chemical cues. The ectoparasitoid Holepyris sylvanidis is known to follow chemical trails released by host larvae of the confused flour beetle, Tribolium confusum, for short-range host location. Although the hexane-extractable trails consist of stable, long-chain cuticular hydrocarbons (CHCs) with low volatility, the kairomonal activity of a trail is lost two days after release. Here, we studied whether this loss of kairomonal activity is due to changes in the chemical trail composition induced by microbial activity. We chemically analyzed trails consisting of hexane extracts of T. confusum larvae after different time intervals past deposition under sterile and non-sterile conditions. GC-MS analyses revealed that the qualitative and quantitative pattern of the long-chain CHCs of larval trails did not significantly change over time, neither under non-sterile nor sterile conditions. Hence, our results show that the loss of kairomonal activity of host trails is not due to microbially induced changes of the CHC pattern of a trail. Interestingly, the kairomonal activity of trails consisting of host larval CHC extracts was recoverable after two days by applying hexane to them. After hexane evaporation, the parasitoids followed the reactivated host trails as they followed freshly laid ones. Cryo-scanning electron microscopy showed that the trails gradually formed filament-shaped microstructures within two days. This self-assemblage of CHCs was reversible by hexane application. Our study suggests that the long-chain CHCs of a host trail slowly undergo solidification by a self-assembling process, which reduces the accessibility of CHCs to the parasitoid’s receptors as such that the trail is no longer eliciting trail-following behavior.

The eukaryotic cell is a smart compartment containing an outer permeable membrane, a cytoskeleton, and functional organelles, presenting part structures for life. The integration of membrane-containing artificial organelles (=polymersomes) into a large microcompartment is a key step towards the establishment of exquisite cellular biomimetics with different membrane properties. Herein, an efficient way to construct a hierarchical multicompartment composed of a hydrogel-filled proteinosome hybrid structure with an outer homogeneous membrane, a smart cytoskeleton-like scaffold, and polymersomes is designed. Specially, this hybrid structure creates a micro-environment for pH-responsive polymersomes to execute a desired substance transport upon response to biological stimuli. Within the dynamic pH-stable skeleton of the protein hydrogels, polymersomes with loaded PEGylated insulin biomacromolecules demonstrate a pH-responsive reversible swelling-deswelling and a desirable, on-demand cargo release which is induced by the enzymatic oxidation of glucose to gluconic acid. This stimulus responsive behavior is realized by tunable on/off states through protonation of the polymersomes membrane under the enzymatic reaction of glucose oxidase, integrated in the skeleton of protein hydrogels. The integration of polymersomes-based hybrid structure into the proteinosome compartment and the stimuli-response on enzyme reactions fulfills the requirements of eukaryotic cell biomimetics in complex architectures and allows mimicking cellular transportation processes.

Whiteflies attach their eggs to plants by implanting the egg pedicel into the epidermis of the underside of leaves. This pedicel works like a wall plug embedded in sealing cement, presenting a smart interconnection, which was exemplarily studied in Trialeurodes vaporariorum eggs on two stages of abaxial leaflets of four cut rose cultivars using a combination of microscopic and biomechanical techniques. The penetration force obtained by piercing single epidermal cells with an insect minuten pin did not significantly correlate with the force which was applied to pull off the greenhouse whitefly eggs from abaxial leaves. A maximum pull-off force of 5.4 mN was measured on young leaves of the rose cultivar ‘Schloss Ippenburg®’, corresponding to maximum 941 times the egg weight. Egg pull-off force significantly differed between cut rose cultivars and leaf ages. On greenhouse whitefly-susceptible cultivars ‘Poesie®’ and ‘Reggae®’, eggs detached, applying less force compared to that on resistant cultivars. Leaf structural features had no significant impact on greenhouse whitefly egg pull-off forces. A major effect of leaf turgor pressure and swelling of colleterial gland secretion (cement) surrounding the whitefly egg is assumed to facilitate the firm interconnection between egg and plant epidermis by a combination of form closure, friction locking, and adhesive bond forming a composite material in the contact region. This bond exhibits a maximum adhesive strength of 12.2 MPa, which is much higher than those in beetle and moth eggs glued to oviposition substrates.

Stem cell bioengineering and therapy require different model systems and materials in different stages of development. If a chemically defined biomatrix system can fulfill most tasks, it can minimize the discrepancy among various setups. By screening biomaterials synthesized through a coacervation-mediated self-assembling mechanism, a biomatrix system optimal for 2D human mesenchymal stromal cell (hMSC) culture and osteogenesis is identified. Its utility for hMSC bioengineering is further demonstrated in coating porous bioactive glass scaffolds and nanoparticle synthesis for esiRNA delivery to knock down the SOX-9 gene with high delivery efficiency. The self-assembled injectable system is further utilized for 3D cell culture, segregated co-culture of hMSC with human umbilical vein endothelial cells (HUVEC) as an angiogenesis model, and 3D bioprinting. Most interestingly, the coating of bioactive glass with the self-assembled biomatrix not only supports the proliferation and osteogenesis of hMSC in the 3D scaffold but also induces the amorphous bioactive glass (BG) scaffold surface to form new apatite crystals resembling bone-shaped plate structures. Thus, the self-assembled biomatrix system can be utilized in various dimensions, scales, and geometries for many different bioengineering applications.

Traction forces of male and female southern green stink bugs Nezara viridula (L.) were measured on adaxial leaves of green beans (Phaseolus vulgaris L. cv. ‘Nagauzura’), peas (Pisum sativum L. cv. ‘Hakuryu’), rice (Oryza sativa L. cv. ‘Mac hin sung’), and soybean (Glycine max [L.] Merr. cv. ‘Enrei’), as well as on glass as a control surface. Bugs attached well on three-dimensionally structured surfaces covered with anti-adhesive epicuticular wax crystals. Strongest pulls were generated on adaxial green bean leaves, corresponding to safety factors (traction force/body weight) of 11.1 and 11.6 in males and females, respectively. These values were slightly lower on soybean (males: 7.4, females: 8.0) and rice leaves (males: 8.9, females: 10.6). Trichomes and papillae are assumed to promote pentatomid bug’s attachment. On tabular, wax-covered pea leaves, safety factors decreased significantly to 1.7 and 1.6, in males and females, respectively. Differently, on non-structured glass, safety factors resembled those on rice and soybean leaves (males: 9.6, females: 8.0). No statistical differences in traction force and safety factor between sexes were detected on any substrate. Surface wettability did not significantly affect the results. Both robust claws and tough adhesive pads enable the N. viridula bugs to grasp and adhere to a wide range of various plant substrates, including such ones covered with anti-adhesive wax crystals. However, tabular, pruinose pea leaves were detected to prevent the foothold of the southern green stink bugs, although pea is known as one of their common host plants.

Formation of extracellular ice at specific positions in the plant interior is a common and probably essential component of plant cold hardiness. Studies on extracellular freezing in spore-bearing plants are, however, scarce. In this study, extracellular ice formation in the cold hardy horsetail Equisetum hyemale L. is analyzed. Horsetails show an extensive system of intercellular air spaces which are probably crucial for internal ice storage during winter. Previous studies emphasized the spacious pith cavity as the main place for ice crystal growth. Shoots were studied during summer and in the frozen state in winter, after natural acclimatization, by using digital (incident light) microscopy, Scanning Electron Microscopy and Cryo Scanning Electron Microscopy. It was shown that the vallecular canals also contain a large share of ice bodies under freezing conditions. The vallecular canals, which are directly seated within the cortex and whose interior is directly connected to the cortex via gaps in the canal wall, were often and rapidly filled with ice. The pith cavity also contained ice, depending on the position along the shoot and the internode. The carinal canals contained almost no ice crystals. Furthermore, some ice crystals were detected in the intercellular spaces of the chlorenchyma and the substomatal chamber. The stomatal antechamber, however, was always ice-free, probably due to the presence of water-repellent wax crystals. The results of this study support available evidence for the crucial role of pre-existing extensive lacunae for extracellular ice formation in E. hyemale . Furthermore, the findings indicate that anatomical details of canal structure and position are important for the pattern of extracellular ice accumulation.

The presence of well-developed, elastic claws on ticks and widely pilose hosts led us to hypothesise that ticks are mostly adapted to attachment and locomotion on rough, strongly corrugated and hairy, felt-like substrates. However, by using a combination of morphological and experimental approaches, we visualised the ultrastructure of attachment devices of Ixodes ricinus and showed that this species adheres more strongly to smooth surfaces than to rough ones. Between paired, elongated, curved, elastic claws, I. ricinus bears a large, flexible, foldable adhesive pad, which represents an adaptation to adhesion on smooth surfaces. Accordingly, ticks attached strongest to glass and to surface profiles similar to those of the human skin, generating safety factors (attachment force relative to body weight) up to 534 (females). Considerably lower attachment force was found on silicone substrates and as a result of thanatosis after jolting.

Flower surfaces play a key role in the interaction with pollinators acting as signals and landing sites to attach to. To test attachment, Carniolan honeybees and greenbottle flies were used. Both species represent pollinators equipped with smooth or hairy tarsal attachment devices, respectively. A combination of microscopic methods and traction force measurements was applied in order to understand and evaluate the efficiency of pollinator attachment to a variety of petal surfaces. Although the petal surface texture influenced the attachment, coevolutionary relationships or adaptations between flower surfaces and pollinator tarsi could not be confirmed. Since pollinators appear to be opportunistic, they are expected to attach to a variety of flower surfaces. Rougher surfaces, including conical and papillate epidermal cells, significantly increased the foothold of flies and honeybees, while flat, tabular epidermal cells covered with microstructures like cuticular folds and epicuticular wax crystals impaired attachment. Carniolan honeybees generated larger forces than greenbottle flies, but the latter showed higher safety factors. However, tendencies in attachment ability toward sufficient and insufficient substrates are similar in flies and bees.

A mixture of resins based on aliphatic esters and carboxylic acids occurs in distantly related genera Peperomia and Roridula , serving different functions as adhesion in seed dispersal and prey capture. According to mechanical characteristics, adhesive secretions on both leaves of the carnivorous flypaper Roridula gorgonias and epizoochorous fruits of Peperomia polystachya were expected to be similar. The chemical analysis of these adhesives turned out to be challenging because of the limited available mass for analysis. Size exclusion chromatography and Fourier transform infrared spectroscopy were suitable methods for the identification of a mixture of compounds, most appropriately containing natural resins based on aliphatic esters and carboxylic acids. The IR spectra of the Peperomia and Roridula adhesive resemble each other; they correspond to that of a synthetic ethylene–vinyl acetate copolymer, but slightly differ from that of natural tree resins. Thus, the pressure sensitive adhesive properties of the plant adhesives are chemically proved. Such adhesives seem to appear independently in distantly related plant lineages, habitats, life forms, as well as plant organs, and serve different functions such as prey capture in Roridula and fruit dispersal in Peperomia. However, more detailed chemical analyses still remain challenging because of the small available volume of plant adhesive.

Green dock beetles Gastrophysa viridula and Colorado potato beetles Leptinotarsa decemlineata having distinctly different body mass and gait habits were compared with respect to their tarsal morphology and attachment ability. The focus laid on shapes and dimensions of tenent setae related to the peeling line, i.e., the sum of widths of all thin-film elements participating in contact. High-speed rotation of the two leaf beetle species attached to the horizontal and vertical sides of a Plexiglass drum resulted in higher attachment forces of the heavier beetle species that has a larger number of tarsal setae and a larger peeling line length. However, normalizing the measured forces with the corresponding peeling line lengths led to a reversed relationship. This allowed us to assume that the design of adhesive setae in different leaf beetle species matches the requirements imposed by their habitats. In accordance with the theory of thin film peeling, tangential forces were found to be higher than normal forces. The attachment system of females was found to exhibit stronger functional efficiency, which can be correlated to the morphology of their setae.

Attachment to surfaces is a major aspect of an animal9s interaction with the environment. Consequently, shaping of the attachment system in relation to weight load and substrate is considered to have occurred mainly by natural selection. However, sexual selection may also be important because many animals attach to their partner during mating. The two hypotheses generate opposing predictions in species where males are smaller than females. Natural selection predicts that attachment ability will scale positively with load, and hence body size, and so will be larger in females than males. Sexual selection predicts attachment forces in males will be larger than those in females, despite the males9 smaller size because males benefit from uninterrupted copulation by stronger attachment to the female. We tested these predictions in the common bedbug Cimex lectularius, a species in which both sexes, as well as nymphs, regularly carry large loads: blood meals of up to 3 times their body weight. By measuring attachment forces to smooth surfaces and analysing in situ fixed copulating pairs and the morphology of attachment devices, we show that: (i) males generate twice the attachment force of females, despite weighing 15% less; (ii) males adhere to females during copulation using hairy tibial adhesive pads; (iii) there are more setae, and more setae per unit area, in the pads of males than in those of females but there is no difference in the shape of the tarsal setae; and (iv) there is an absence of hairy tibial attachment pads and a low attachment force in nymphs. These results are consistent with a sexually selected function of attachment in bedbugs. Controlling sperm transfer and mate guarding by attaching to females during copulation may also shape the evolution of male attachment structures in other species. More generally, we hypothesise the existence of an arms race in terms of male attachment structures and female counterparts to impede attachment, which may result in a similar evolutionary diversification to male genitalia.

Attachment to surfaces is a major aspect of an animal's interaction with the environment. Consequently, shaping of the attachment system in relation to weight load and substrate is considered to have occurred mainly by natural selection. However, sexual selection may also be important because many animals attach to their partner during mating. The two hypotheses generate opposing predictions in species where males are smaller than females. Natural selection predicts that attachment ability will scale positively with load, and hence body size, and so will be larger in females than males. Sexual selection predicts attachment forces in males will be larger than those in females, despite the males' smaller size because males benefit from uninterrupted copulation by stronger attachment to the female. We tested these predictions in the common bedbug

In this article, we demonstrate a procedure to investigate sperm charge distribution by electrostatic sperm-particle interactions. We fabricated and investigated differently charged particles and their attachment distribution on the bovine sperm membrane. We observed the sperm-particle attachment sites using bright field and cryo-scanning electron microscopy combined with energy-dispersive X-ray analysis. Our findings suggest that the charge distribution of the sperm membrane is not uniform and although the overall net charge of the sperm cell is negative, positively charged areas are especially found on the sperm heads. We test the newly developed method to investigate the dynamic charge distribution of the sperm cell membrane upon maturation induced by heparin, as a representation of the multitude of changes during the development of a sperm.

The presence of well-developed, elastic claws on ticks and widely pilose hosts led us to hypothesise that ticks are mostly adapted to attachment and locomotion on rough, strongly corrugated and hairy, felt-like substrates. However, by using a combination of morphological and experimental approaches, we visualised the ultrastructure of attachment devices of

Insects live in a three-dimensional space, and need to be able to attach to different types of surfaces in a variety of environmental and behavioral contexts. Adult leaf beetles possess great attachment ability due to their hairy attachment pads. In contrast, their larvae depend on smooth pads to attach to the same host plant. We tested friction forces generated by larvae and adults of dock leaf beetles Gastrophysa viridula on different rough surfaces, and found that adults generate much higher attachment to various substrates than larvae, but are more susceptible to completely losing attachment ability on surfaces with “critical” roughness. Furthermore, sex-specific setal morphology has the effect that attachment forces of male adults are generally higher than those of females when adjusted for body weight. The results are discussed in the context of development, ecology, and changing behavioral strategies of successive life stages.

SUMMARYThe influence of surface roughness on the attachment ability of insects has been repeatedly reported. In previous experiments, complex surface topographies were used as test substrates, whereas periodical structures have so far been neglected. In the present study, traction experiments with adult beetles Gastrophysa viridula and Leptinotarsa decemlineata were carried out to study the influence of surfaces, structured with periodical wrinkles, on insect attachment. Force measurements were carried out on male and female insects, both intact and after removal of claws, performing tethered walking on five polydimethylsiloxane substrates: (i) smooth, non-structured (control), (ii–v) structured with wrinkles of different wavelengths (366, 502, 911 and 25,076 nm). In two test series, beetles walked either perpendicular or parallel to the wrinkle alignment. Adults of G. viridula produced generally higher forces than those of L. decemlineata. The results show that the alignment of wrinkles had no significant influence on the force generation by beetles, probably because of the skewed position of their tarsomeres relative to the substrates. In both sexes, the highest force values were obtained on surfaces with wrinkles of 25 μm wavelength. On other wrinkled substrates, forces were significantly reduced in both males and females compared with the smooth, flat control, with the minimum force achieved on wrinkles with a wavelength of 911 nm.

Codling moths, Cydia pomonella L. (Lepidoptera, Tortricidae), of the first generation deposit eggs on apple leaves in the vicinity of small fruits. The choice of the suitable oviposition sites and proper fixation of eggs are expected to be crucial factors for the survival of the offspring. In this study, we investigated egg adhesion of the codling moth to leaf surfaces of different cultivars of the domestic apple, Malus domestica Borkh., by measuring the pull-off force required to detach the eggs from leaves. Since surface features may influence insect egg adhesion, morphological and physicochemical properties (wettability, free surface energy) of these leaf surfaces were analyzed. Furthermore, eggs and their adhesives covering leaf surfaces were visualized. Eggs on the smooth upper leaf surfaces of all tested cultivars required significantly similar pull-off forces to be detached, at a total average of 6.0 mN. Up to 2–3 times stronger pull-off forces had to be applied to detach eggs from trichome-covered lower leaves, and these forces differed significantly between cultivars. The role of leaf surface properties is discussed in the context of egg adhesion, oviposition site choice, female attachment, as well as neonate locomotion speed and survival. The obtained results shed light on the susceptibility of various apple cultivars and leaf surfaces to the infestation of apple trees by first-generation codling moths.

The larvae of some sawfly species belonging to the family Tenthredinidae (Hymenoptera) are capable of 'easy bleeding', an anti-predator defence strategy based on a specialised cuticle that can readily break, which frees droplets of distasteful haemolymph. Using high-resolution cryo-scanning electron microscopy, we compared the cuticle surface between easy bleeder (Rhadinoceraea micans, Phymatocera aterrima, Aneugmenus padi) and non-easy bleeder (Strongylogaster multifasciata, Nematus pavidus, Arge pagana) sawfly species. We detected crystalline waxes only on the cuticle surface of easy bleeders. Wax crystals varied in shape and dimension depending on species. We assume the reduction of surface wettability by oozed haemolymph to be the primary function of the wax crystal coverage in the easy bleeding defence strategy.

In a natural environment, insects live in different microhabitats varying in their humidity. Because insect adhesive mechanism at least partly relies on the capillary force, it is natural to assume that environmental humidity may considerably influence insect attachment. However, this aspect has been neglected in the literature so far. We present the first experimental study demonstrating the influence of the exposure to moist surfaces on the attachment of Colorado potato beetles Leptinotarsa decemlineata. Male beetles were kept at either a dry or moist condition with varying duration of stay for a period up to 160 min. Using centrifugal force tester, their friction forces were then measured on a plexiglas surface. The results show significant differences in force depending on the kind of pre-conditioning. A temporary stay in dry environment had no significant impact on the generated friction forces within the tested time scale. After walking on moist filter paper, forces increased significantly up to 171% of the initial forces measured after 1 min of preconditioning. These results show that insects of the same species may be strongly influenced in their attachment by environmental conditions. The second important conclusion is that results of different experimental studies on insect attachment can hardly be compared if they were performed under different environmental conditions.

The mirid bug Pameridea roridulae lives mutalistically on the protocarnivorous plant Roridula gorgonias. The latter resembles an effective, three-dimensional flypaper trap which captures numerous flying insects. We have recently shown that P. roridulae bugs are not trapped by the plant, because they are covered with a layer of epicuticular grease, which is considerably thicker than in other insects. The present study demonstrates that the bugs’ morphology and locomotory characteristics also contribute to their specialisation for life on the adhesive plant surface. A structural analysis of the mirid bug’s attachment system, and an experimental study on its attachment ability were carried out. In traction force tests, maximum forces of 8.8 mN were measured on adaxial R. gorgonias leaves, corresponding to 126 times the bug’s body weight. On smooth surfaces, generated forces were only 47 times the bug’s body weight. Compared to closely related mirid bug species avoiding contact with plant adhesive secretion, P. roridulae is distinctly stronger and heavier, and holds its body close to the plant substrate. Two locomotion strategies on the glandular hairy plant surfaces are suggested for mirid bug species from the tribus Dicyphini: (1) avoidance strategy, characterised by the slim body held at a large distance from the plant surface by using long, slender legs, and (2) defense strategy, where trapping of the heavy bugs, situated close to the plant surface, is overcome by generating strong forces during locomotion and by having a thick anti-adhesive epicuticular greasy layer on the bugs’ cuticle.

Pits of a softwood (Pinus wallichiana) and a hardwood (Mallotus japonicus) were studied by Cryo-scanning electron microscopy (Cryo-SEM). The samples were chemically untreated and fully hydrated during freezing. Tori of P. wallichiana were frequently aspirated. It is not clear whether torus aspiration was caused by the freezing process or other factors during preparation. Aspirated tori had a turgid appearance. Offcenter aspirated tori which did not completely cover the pit pore could be detected. The margo strands were usually quite large and fanned out into fibrillar structures at the pit border. Pit membranes of M. japonicus had a very granular appearance. No fibrillar structures, different layers or pores could be detected. The granular structures may have developed from a continuous layer covering the pit membrane during freezing. Cryo-SEM is discussed as a further suitable tool for obtaining novel information about the native state of pit membranes. Future studies are needed to validate whether all observed features represent characteristics of the native state.

SUMMARYThe flypaper trap of the protocarnivorous plant Roridula gorgoniasis known to capture various insects, even those having a considerable body size, by using an adhesive, visco-elastic resinous secretion released by glandular trichomes of different dimensions. However, recent experimental studies have shown that the adhesion of long tentacle-shaped trichome secretion is not as strong as previously assumed. One may then ask why this flypaper trap is so highly effective. In the present study, we compared geometry, flexibility and the adhesive properties of secretion in different sized trichomes. We have analysed the gross morphology of the plant and its surfaces using light and cryo-scanning electron microscopy. Trichomes'stiffness and the adhesive properties of their secretion on different surfaces were measured. A combination of structural and experimental results, presented in this study, let us suggest that R. gorgonias represents a three-dimensional trap consisting of three functional hierarchical levels(plant, leaves and trichomes). According to their size, we classified three types of trichomes having a particular arrangement on the leaf. The longest trichomes are more flexible and less adhesive compared with the shortest ones. The latter are 48 times stiffer and their secretion has a 9 times higher adhesive strength. Our data support the hypothesis that the shortest trichomes are adapted to strong, long-term adherence to prey insects, and that the longest trichomes are responsible for initial trapping and entanglement function.

Trichome-based tomato resistance offers the potential to reduce pesticide use, but its compatibility with biological control remains poorly understood. We evaluated Episyrphus balteatus De Geer (Diptera, Syrphidae), an efficient aphidophagous predator, as a potential biological control agent of Myzus persicae Sulzer (Hemiptera, Aphididae) on trichome-bearing tomato cultivars. Episyrphus balteatus’ foraging and oviposition behavior, as well as larval mobility and aphid accessibility, were compared between two tomato cultivars (Lycopersicon esculentum Mill. ‘Moneymaker’ and ‘Roma’) and two other crop plants; broad bean (Vicia faba L.) and potato (Solanum tuberosum L.). Hoverfly adults landed and laid more eggs on broad beans than on three species of Solanaceae. Hoverfly larval movement was drastically reduced on tomato, and a high proportion of hoverfly larvae fell from the plant before reaching aphid prey. After quantifying trichome abundance on each of these four plants, we suggest that proprieties of the plant surface, specifically trichomes, are a key factor contributing to reduced efficacy of E. balteatus as a biological agent for aphid control on tomatoes.

This study represents an investigation of surface-related plant–insect interactions. Surface micro-morphology of leaflets in pea (Pisum sativum) with wild-type crystalline surface waxes (waxy) and with reduced crystalline surface waxes (glossy) caused by a mutation (wel) were studied using various microscopy techniques. The free surface energy of these plant surfaces was estimated using contact angles of droplets of three different liquids. The morphological study of the attachment system in the ladybird beetle Cryptolaemus montrouzieri was combined with measurements of attachment (traction) forces, generated by beetles on these plant substrates. Differences were found in wax crystal shape, dimensions, and density between the adaxial and abaxial surfaces of waxy and glossy plants. The crystalline wax was not completely eliminated in the glossy plant: it was only slightly reduced on the adaxial side and underwent greater changes on the abaxial side. The free surface energy for both surfaces of both pea types was rather low with strongly predominating dispersion component. Insects generated low traction forces on all intact plant surfaces studied, except the abaxial surface of the glossy plant, on which the force was greater. After being treated with chloroform, all the surfaces allowed much higher traction forces. It is demonstrated that the difference in the crystal length and density of the epicuticular wax coverage within the observed range did not influence wettability of surfaces, but affected insect attachment. The reduction in insect attachment force on plant surfaces, covered with the crystalline wax, is explained by the decrease of the real contact area between setal tips of beetles and the substrate.