W. Federle - Academia.edu (original) (raw)
Papers by W. Federle
Journal of Experimental Biology, Jan 2010
"Insects possess adhesive organs that allow attachment to diverse surfaces. Efficient adhesion mu... more "Insects possess adhesive organs that allow attachment to diverse surfaces. Efficient adhesion must be retained throughout their lifetime even when pads are exposed to contamination. Many insects groom their adhesive structures, but it is possible that self- cleaning properties also play an important role. We measured attachment forces of insect pads on glass after contamination with microspheres and found that both smooth pads (stick insects: Carausius morosus) and hairy pads (dock beetles: Gastrophysa viridula) exhibit self-cleaning. Contaminated pads recovered high levels of adhesion after only eight simulated steps; this was accompanied by the deposition of spheres. Self-cleaning was strongly enhanced by shear movements, and only beetle pads showed the ability to self-clean during purely perpendicular pull-offs. Hairy pads also self-cleaned more efficiently than smooth pads for both large (45um) and small (1um) particle sizes. However, the beetles’ self-cleaning was not superior to smooth pads when contaminated with 10um beads. This limitation of self-cleaning is explained by the coincidence of bead diameter and inter-
seta distance, which caused beads to remain trapped in between setae."
Journal of Experimental Biology, 2009
Many beetles employ arrays of adhesive setae to control attachment during locomotion. Here we inv... more Many beetles employ arrays of adhesive setae to control attachment during locomotion. Here we investigate whether and how variation in seta structure, both between sexes and between tarsal pads on the same leg, determines the mechanical properties and adhesive performance of fibrillar arrays. We vertically compressed individual adhesive pads to determine their effective elastic modulus. Distal adhesive arrays were significantly softer than middle and proximal ones. Variation in stiffness was mainly due to different seta diameters, but calculated elastic moduli of seta cuticle were relatively constant at 5-16 GPa. Consistent with their greater compliance, distal pads generated higher adhesion and friction on rough substrates. However, the greater stiffness of proximal pads conveys a superior ability to push. Proximal pads of males were less direction dependent than distal pads and generated larger pushing forces in the distal and lateral directions. In females, proximal pads also produced higher friction forces than distal pads, but only in the lateral direction. Video recordings of vertically climbing beetles confirmed that each pad was used differently. When legs above the body centre of gravity were pulling, beetles mainly engaged the distal pads, whereas legs below the centre of gravity mainly pushed with the proximal pads. Attachment performance was additionally compared between sexes on different substrates. Our findings demonstrate the presence of sex-specific specialisations of the fibrillar system as well as a division of labour between different adhesive pads on the same tarsus.
Journal of Evolutionary Biology, 2012
Carnivorous plants of the genus Nepenthes have evolved a striking diversity of pitcher traps that... more Carnivorous plants of the genus Nepenthes have evolved a striking diversity of pitcher traps that rely on specialized slippery surfaces for prey capture. With a comparative study of trap morphology, we show that Nepenthes pitcher plants have evolved specific adaptations for the use of either one of two distinct trapping mechanisms: slippery wax crystals on the inner pitcher wall and 'insect aquaplaning' on the wet upper rim (peristome). Species without wax crystals had wider peristomes with a longer inward slope. Ancestral state reconstructions identified wax crystal layers and narrow, symmetrical peristomes as ancestral, indicating that wax crystals have been reduced or lost multiple times independently. Our results complement recent reports of nutrient source specializations in Nepenthes and suggest that these specializations may have driven speciation and rapid diversification in this genus.
Integrative and Comparative Biology, 2002
SYNOPSIS. Many animals that locomote by legs possess adhesive pads. Such organs are rapidly relea... more SYNOPSIS. Many animals that locomote by legs possess adhesive pads. Such organs are rapidly releasable and adhesive forces can be controlled during walking and running. This capacity results from the interaction of adhesive with complex mechanical systems. Here we present an integrative study of the mechanics and adhesion of smooth attachment pads (arolia) in Asian Weaver ants (Oecophylla smaragdina). Arolia can be unfolded and folded back with each step. They are extended either actively by contraction of the claw flexor muscle or passively when legs are pulled toward the body. Regulation of arolium use and surface attachment includes purely mechanical control inherent in the arrangement of the claw flexor system.
Insectes Sociaux, 2001
A key adaptation of obligate plant-ants inhabiting tropical myrmecophytes is the capacity to chew... more A key adaptation of obligate plant-ants inhabiting tropical myrmecophytes is the capacity to chew entrance holes into domatium walls. Our study of the factors determining ant entrance hole location in the ant-plant genus Macaranga (Euphorbiaceae) revealed a complex pattern caused by adaptations of both the host plants and their ant partners.
Insectes Sociaux, 1998
In the tropical peat swamp forests of South-East Asia, the ant-plant Macaranga puncticulata is sp... more In the tropical peat swamp forests of South-East Asia, the ant-plant Macaranga puncticulata is specifically associated with Camponotus (Colobopsis) sp. 1 (Formicidae: Formicinae), a member of the C. saundersi-group. This ant shows a variety of adaptations to its plant-bound mode of life. The queens are capable of locating young M. puncticulata plants inside the forest and of chewing entrance holes into the domatia by themselves. C. (Colobopsis) sp. 1 nests were found exclusively inside the domatia of M. puncticulata. The diet consisted predominantly of host plant resources (food bodies and extrafloral nectar), but insect prey were taken too. In contrast to all the other obligate ant associates of Macaranga, C. (Colobopsis) sp. 1 never cultivated any scale insects. Nevertheless, tending Homoptera ("trophobiosis") is indeed included in the behavioral repertoire, but the ants showed this capacity only in experiments in which the host plants had been completely deprived of extrafloral nectaries. Large C. (Colobopsis) sp.1 colonies are polydomous and can extend over up to 20 M. puncticulata trees. There is strong intraspecific competition for host plants during several stages of the colony development. We observed conspicuous pushing fights between queens that tried to found colonies on the same young plant. C. (Colobopsis) sp.1 workers were capable of removing water from flooded domatium chambers. They quickly gathered around fresh injuries to M. puncticulata. Herbivorous insects were fiercely attacked and either driven away from the plant or captured as prey. Moreover, workers often pruned vines that came into contact with their host trees. We could show that colonization by C. (Colobopsis) sp.1 is beneficial for M. puncticulata, since the ants effectively reduced herbivory and plant competition.
Functional Ecology, 2012
ABSTRACT 1. Beneficial 'services' in mutualistic interactions have often not evol... more ABSTRACT 1. Beneficial 'services' in mutualistic interactions have often not evolved de novo, but from ancestral traits that had a function before the emergence of the association. These traits can then acquire novel functions in a mutualism. Even in many close insect-plant relationships, the services provided by each partner are still unclear. 2. In the well-known association between the carnivorous pitcher plant, Nepenthes bicalcarata, and Camponotus schmitzi ants in Borneo, the ants benefit by receiving food and nesting space in swollen, hollow pitcher tendrils, but the benefits to the plant are less clear. Previous studies have suggested that the ants protect against herbivory, prevent putrefaction of pitchers by removing prey items from them or increase the pitcher's prey retention rate by attacking pitcher visitors. 3. Field observations showed that C. schmitzi ants regularly clean the pitcher rim (peristome), which is the main surface responsible for prey capture. We found that this behaviour increases the carnivorous plant's prey capture efficiency and helps to maintain it over the pitcher's life span. Running tests with Oecophylla smaragdina ants on colonised and ant-free older pitchers demonstrated 45·8% higher capture efficiency in pitchers inhabited by C. schmitzi. Head counts of trapped ants showed that C. schmitzi-colonised pitchers indeed captured significantly (45·2%) more prey than uncolonised pitchers of the same age. 4. The peristomes of ant-free older pitchers were strongly contaminated by fungal hyphae and other particles. Experimental contamination of clean pitcher peristomes with starch also strongly reduced capture efficiency. While the peristome was cleaned rapidly in ant-colonised pitchers and capture efficiency returned to the previous level within approximately 1 week, no cleaning and recovery were observed in ant-free pitchers. 5. Within the genus Nepenthes, N. bicalcarata has exceptionally long-lived pitchers. We propose that C. schmitzi ants benefit N. bicalcarata by keeping the pitchers effective over long periods of time, likely allowing the plant to acquire more nutrients per pitcher and thereby minimise pitcher construction costs. 6. Our findings demonstrate that the cleaning behaviour typical of many plant-ants has acquired a novel function in this ant-plant association, giving rise to a new type of myrmecotrophic mutualism.
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2008
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2009
forces required for a bird to accelerate during takeoff or landing. Using high-speed video, we ob... more forces required for a bird to accelerate during takeoff or landing. Using high-speed video, we obtained kinematics of pigeons (Columba livia) taking off from and landing on a perch. Birds took off with horizontal body angles and landed with their bodies pitched upward, occasionally beyond the vertical. Dramatic differences were also found in the downstroke plane angle, which was up to +45°during takeoff and as low as −20°during the final wingbeats of landing. During takeoff, the geometric angle of attack during mid-downstroke was as shallow as 0°; during landing, it increased to above 45°. In both flight modes, the tail was broadly flared.
We describe a scalable method to fabricate nanopatterned bioinspired dry adhesives using colloida... more We describe a scalable method to fabricate nanopatterned bioinspired dry adhesives using colloidal lithography. Close-packed monolayers of polystyrene particles were formed at the air/water interface, on which polydimethylsiloxane (PDMS) was applied. The order of the colloidal monolayer and the immersion depth of the particles were tuned by altering the pH and ionic strength of the water. Initially, PDMS completely wetted the air/water interface outside the monolayer, thereby compressing the monolayer as in a Langmuir trough; further application of PDMS subsequently covered the colloidal monolayers. PDMS curing and particle extraction resulted in elastomers patterned with nanodimples. Adhesion and friction of these nanopatterned surfaces with varying dimple depth were studied using a spherical probe as a counter-surface. Compared with smooth surfaces, adhesion of nanopatterned surfaces was enhanced, which is attributed to an energy-dissipating mechanism during pull-off. All nanopatterned surfaces showed a significant decrease in friction compared with smooth surfaces.
Journal of Experimental Biology, Jan 2010
"Insects possess adhesive organs that allow attachment to diverse surfaces. Efficient adhesion mu... more "Insects possess adhesive organs that allow attachment to diverse surfaces. Efficient adhesion must be retained throughout their lifetime even when pads are exposed to contamination. Many insects groom their adhesive structures, but it is possible that self- cleaning properties also play an important role. We measured attachment forces of insect pads on glass after contamination with microspheres and found that both smooth pads (stick insects: Carausius morosus) and hairy pads (dock beetles: Gastrophysa viridula) exhibit self-cleaning. Contaminated pads recovered high levels of adhesion after only eight simulated steps; this was accompanied by the deposition of spheres. Self-cleaning was strongly enhanced by shear movements, and only beetle pads showed the ability to self-clean during purely perpendicular pull-offs. Hairy pads also self-cleaned more efficiently than smooth pads for both large (45um) and small (1um) particle sizes. However, the beetles’ self-cleaning was not superior to smooth pads when contaminated with 10um beads. This limitation of self-cleaning is explained by the coincidence of bead diameter and inter-
seta distance, which caused beads to remain trapped in between setae."
Journal of Experimental Biology, 2009
Many beetles employ arrays of adhesive setae to control attachment during locomotion. Here we inv... more Many beetles employ arrays of adhesive setae to control attachment during locomotion. Here we investigate whether and how variation in seta structure, both between sexes and between tarsal pads on the same leg, determines the mechanical properties and adhesive performance of fibrillar arrays. We vertically compressed individual adhesive pads to determine their effective elastic modulus. Distal adhesive arrays were significantly softer than middle and proximal ones. Variation in stiffness was mainly due to different seta diameters, but calculated elastic moduli of seta cuticle were relatively constant at 5-16 GPa. Consistent with their greater compliance, distal pads generated higher adhesion and friction on rough substrates. However, the greater stiffness of proximal pads conveys a superior ability to push. Proximal pads of males were less direction dependent than distal pads and generated larger pushing forces in the distal and lateral directions. In females, proximal pads also produced higher friction forces than distal pads, but only in the lateral direction. Video recordings of vertically climbing beetles confirmed that each pad was used differently. When legs above the body centre of gravity were pulling, beetles mainly engaged the distal pads, whereas legs below the centre of gravity mainly pushed with the proximal pads. Attachment performance was additionally compared between sexes on different substrates. Our findings demonstrate the presence of sex-specific specialisations of the fibrillar system as well as a division of labour between different adhesive pads on the same tarsus.
Journal of Evolutionary Biology, 2012
Carnivorous plants of the genus Nepenthes have evolved a striking diversity of pitcher traps that... more Carnivorous plants of the genus Nepenthes have evolved a striking diversity of pitcher traps that rely on specialized slippery surfaces for prey capture. With a comparative study of trap morphology, we show that Nepenthes pitcher plants have evolved specific adaptations for the use of either one of two distinct trapping mechanisms: slippery wax crystals on the inner pitcher wall and 'insect aquaplaning' on the wet upper rim (peristome). Species without wax crystals had wider peristomes with a longer inward slope. Ancestral state reconstructions identified wax crystal layers and narrow, symmetrical peristomes as ancestral, indicating that wax crystals have been reduced or lost multiple times independently. Our results complement recent reports of nutrient source specializations in Nepenthes and suggest that these specializations may have driven speciation and rapid diversification in this genus.
Integrative and Comparative Biology, 2002
SYNOPSIS. Many animals that locomote by legs possess adhesive pads. Such organs are rapidly relea... more SYNOPSIS. Many animals that locomote by legs possess adhesive pads. Such organs are rapidly releasable and adhesive forces can be controlled during walking and running. This capacity results from the interaction of adhesive with complex mechanical systems. Here we present an integrative study of the mechanics and adhesion of smooth attachment pads (arolia) in Asian Weaver ants (Oecophylla smaragdina). Arolia can be unfolded and folded back with each step. They are extended either actively by contraction of the claw flexor muscle or passively when legs are pulled toward the body. Regulation of arolium use and surface attachment includes purely mechanical control inherent in the arrangement of the claw flexor system.
Insectes Sociaux, 2001
A key adaptation of obligate plant-ants inhabiting tropical myrmecophytes is the capacity to chew... more A key adaptation of obligate plant-ants inhabiting tropical myrmecophytes is the capacity to chew entrance holes into domatium walls. Our study of the factors determining ant entrance hole location in the ant-plant genus Macaranga (Euphorbiaceae) revealed a complex pattern caused by adaptations of both the host plants and their ant partners.
Insectes Sociaux, 1998
In the tropical peat swamp forests of South-East Asia, the ant-plant Macaranga puncticulata is sp... more In the tropical peat swamp forests of South-East Asia, the ant-plant Macaranga puncticulata is specifically associated with Camponotus (Colobopsis) sp. 1 (Formicidae: Formicinae), a member of the C. saundersi-group. This ant shows a variety of adaptations to its plant-bound mode of life. The queens are capable of locating young M. puncticulata plants inside the forest and of chewing entrance holes into the domatia by themselves. C. (Colobopsis) sp. 1 nests were found exclusively inside the domatia of M. puncticulata. The diet consisted predominantly of host plant resources (food bodies and extrafloral nectar), but insect prey were taken too. In contrast to all the other obligate ant associates of Macaranga, C. (Colobopsis) sp. 1 never cultivated any scale insects. Nevertheless, tending Homoptera ("trophobiosis") is indeed included in the behavioral repertoire, but the ants showed this capacity only in experiments in which the host plants had been completely deprived of extrafloral nectaries. Large C. (Colobopsis) sp.1 colonies are polydomous and can extend over up to 20 M. puncticulata trees. There is strong intraspecific competition for host plants during several stages of the colony development. We observed conspicuous pushing fights between queens that tried to found colonies on the same young plant. C. (Colobopsis) sp.1 workers were capable of removing water from flooded domatium chambers. They quickly gathered around fresh injuries to M. puncticulata. Herbivorous insects were fiercely attacked and either driven away from the plant or captured as prey. Moreover, workers often pruned vines that came into contact with their host trees. We could show that colonization by C. (Colobopsis) sp.1 is beneficial for M. puncticulata, since the ants effectively reduced herbivory and plant competition.
Functional Ecology, 2012
ABSTRACT 1. Beneficial 'services' in mutualistic interactions have often not evol... more ABSTRACT 1. Beneficial 'services' in mutualistic interactions have often not evolved de novo, but from ancestral traits that had a function before the emergence of the association. These traits can then acquire novel functions in a mutualism. Even in many close insect-plant relationships, the services provided by each partner are still unclear. 2. In the well-known association between the carnivorous pitcher plant, Nepenthes bicalcarata, and Camponotus schmitzi ants in Borneo, the ants benefit by receiving food and nesting space in swollen, hollow pitcher tendrils, but the benefits to the plant are less clear. Previous studies have suggested that the ants protect against herbivory, prevent putrefaction of pitchers by removing prey items from them or increase the pitcher's prey retention rate by attacking pitcher visitors. 3. Field observations showed that C. schmitzi ants regularly clean the pitcher rim (peristome), which is the main surface responsible for prey capture. We found that this behaviour increases the carnivorous plant's prey capture efficiency and helps to maintain it over the pitcher's life span. Running tests with Oecophylla smaragdina ants on colonised and ant-free older pitchers demonstrated 45·8% higher capture efficiency in pitchers inhabited by C. schmitzi. Head counts of trapped ants showed that C. schmitzi-colonised pitchers indeed captured significantly (45·2%) more prey than uncolonised pitchers of the same age. 4. The peristomes of ant-free older pitchers were strongly contaminated by fungal hyphae and other particles. Experimental contamination of clean pitcher peristomes with starch also strongly reduced capture efficiency. While the peristome was cleaned rapidly in ant-colonised pitchers and capture efficiency returned to the previous level within approximately 1 week, no cleaning and recovery were observed in ant-free pitchers. 5. Within the genus Nepenthes, N. bicalcarata has exceptionally long-lived pitchers. We propose that C. schmitzi ants benefit N. bicalcarata by keeping the pitchers effective over long periods of time, likely allowing the plant to acquire more nutrients per pitcher and thereby minimise pitcher construction costs. 6. Our findings demonstrate that the cleaning behaviour typical of many plant-ants has acquired a novel function in this ant-plant association, giving rise to a new type of myrmecotrophic mutualism.
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2008
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2009
forces required for a bird to accelerate during takeoff or landing. Using high-speed video, we ob... more forces required for a bird to accelerate during takeoff or landing. Using high-speed video, we obtained kinematics of pigeons (Columba livia) taking off from and landing on a perch. Birds took off with horizontal body angles and landed with their bodies pitched upward, occasionally beyond the vertical. Dramatic differences were also found in the downstroke plane angle, which was up to +45°during takeoff and as low as −20°during the final wingbeats of landing. During takeoff, the geometric angle of attack during mid-downstroke was as shallow as 0°; during landing, it increased to above 45°. In both flight modes, the tail was broadly flared.
We describe a scalable method to fabricate nanopatterned bioinspired dry adhesives using colloida... more We describe a scalable method to fabricate nanopatterned bioinspired dry adhesives using colloidal lithography. Close-packed monolayers of polystyrene particles were formed at the air/water interface, on which polydimethylsiloxane (PDMS) was applied. The order of the colloidal monolayer and the immersion depth of the particles were tuned by altering the pH and ionic strength of the water. Initially, PDMS completely wetted the air/water interface outside the monolayer, thereby compressing the monolayer as in a Langmuir trough; further application of PDMS subsequently covered the colloidal monolayers. PDMS curing and particle extraction resulted in elastomers patterned with nanodimples. Adhesion and friction of these nanopatterned surfaces with varying dimple depth were studied using a spherical probe as a counter-surface. Compared with smooth surfaces, adhesion of nanopatterned surfaces was enhanced, which is attributed to an energy-dissipating mechanism during pull-off. All nanopatterned surfaces showed a significant decrease in friction compared with smooth surfaces.