Structural Diversity of Arthropod Biophotonic Nanostructures Spans Amphiphilic Phase-Space.

Many organisms, especially arthropods, produce vivid interference colors using diverse mesoscopic (100-350 nm) integumentary biophotonic nanostructures that are increasingly being investigated for technological applications. Despite a century of interest, precise structural knowledge of many biophotonic nanostructures and the mechanisms controlling their development remain tentative, when such knowledge can open novel biomimetic routes to facilely self-assemble tunable, multifunctional materials. Here, we use synchrotron small-angle X-ray scattering and electron microscopy to characterize the photonic nanostructure of 140 integumentary scales and setae from ∼127 species of terrestrial arthropods in 85 genera from 5 orders. We report a rich nanostructural diversity, including triply periodic bicontinuous networks, close-packed spheres, inverse columnar, perforated lamellar, and disordered spongelike morphologies, commonly observed as stable phases of amphiphilic surfactants, block copolymer, and lyotropic lipid-water systems. Diverse arthropod lineages appear to have independently evolved to utilize the self-assembly of infolding lipid-bilayer membranes to develop biophotonic nanostructures that span the phase-space of amphiphilic morphologies, but at optical length scales.

Correction: A novel power-amplified jumping behavior in larval beetles (Coleoptera: Laemophloeidae).

[This corrects the article DOI: 10.1371/journal.pone.0256509.].

A novel power-amplified jumping behavior in larval beetles (Coleoptera: Laemophloeidae).

Larval insects use many methods for locomotion. Here we describe a previously unknown jumping behavior in a group of beetle larvae (Coleoptera: Laemophloeidae). We analyze and describe this behavior in Laemophloeus biguttatus and provide information on similar observations for another laemophloeid species, Placonotus testaceus. Laemophloeus biguttatus larvae precede jumps by arching their body while gripping the substrate with their legs over a period of 0.22 ± 0.17s. This is followed by a rapid ventral curling of the body after the larvae releases its grip that launches them into the air. Larvae reached takeoff velocities of 0.47 ± 0.15 m s-1 and traveled 11.2 ± 2.8 mm (1.98 ± 0.8 body lengths) horizontally and 7.9 ± 4.3 mm (1.5 ± 0.9 body lengths) vertically during their jumps. Conservative estimates of power output revealed that some but not all jumps can be explained by direct muscle power alone, suggesting Laemophloeus biguttatus may use a latch-mediated spring actuation mechanism (LaMSA) in which interaction between the larvae's legs and the substrate serves as the latch. MicroCT scans and SEM imaging of larvae did not reveal any notable modifications that would aid in jumping. Although more in-depth experiments could not be performed to test hypotheses on the function of these jumps, we posit that this behavior is used for rapid locomotion which is energetically more efficient than crawling the same distance to disperse from their ephemeral habitat. We also summarize and discuss jumping behaviors among insect larvae for additional context of this behavior in laemophloeid beetles.

Phylogeny, classification and evolution of ladybird beetles (Coleoptera: Coccinellidae) based on simultaneous analysis of molecular and morphological data.

Ladybird beetles (family Coccinellidae) are a species-rich, ecologically diverse group of substantial agricultural significance, yet have been consistently problematic to classify, with evolutionary relationships poorly understood. In order to identify major clades within Coccinellidae, evaluate the current classification system, and identify likely drivers of diversification in this polyphagous group, we conducted the first simultaneous Bayesian analysis of morphological and multi-locus molecular data for any beetle family. Addition of morphological data significantly improved phylogenetic resolution and support for early diverging lineages, thereby better resolving evolutionary relationships than either data type alone. On the basis of these results, we formally recognize the subfamilies Microweisinae and Coccinellinae sensuSlipinski (2007). No significant support was found for the subfamilies Coccidulinae, Scymninae, Sticholotidinae, or Ortaliinae. Our phylogenetic results suggest that the evolutionary success of Coccinellidae is in large part attributable to the exploitation of ant-tended sternorrhynchan insects as a food source, enabled by the key innovation of unusual defense mechanisms in larvae.

A review of the distribution and host plant associations of the platypodine ambrosia beetles (Coleoptera: Curculionidae: Platypodinae) of Australia, with an electronic species identification key.

Ambrosia beetles (Platypodinae and some Scolytinae) are ecologically and economically important weevils (Coleoptera: Curculionidae) that develop within the sapwood and heartwood of woody plants, and their larval and adult stages are dependent on fungal symbionts. Platypodinae mostly occur in tropical and subtropical biomes, with a few species occurring in temperate regions. Australia has 44 recorded platypodine species including 13 species which may only have been intercepted at or near ports of entries and are without established populations in Australia. The host tree associations and biogeography of Australian Platypodinae are largely undocumented, and no comprehensive identification key exists. Here, we review species records, host tree associations, biogeographic distributions, and morphological characteristics of Australian Platypodinae. For this, we examined collection specimens, monographs, catalogues, taxonomic inventories, journal articles and online databases, and developed an electronic LUCID identification key for 36 species recorded in Australia. This review and identification key will be a valuable resource for forestry managers and biosecurity officers and will support diagnostics and future research of these beetles, their biology, and ecological interactions.

Gold bugs and beyond: a review of iridescence and structural colour mechanisms in beetles (Coleoptera).

Members of the order Coleoptera are sometimes referred to as 'living jewels', in allusion to the strikingly diverse array of iridescence mechanisms and optical effects that have arisen in beetles. A number of novel and sophisticated reflectance mechanisms have been discovered in recent years, including three-dimensional photonic crystals and quasi-ordered coherent scattering arrays. However, the literature on beetle structural coloration is often redundant and lacks synthesis, with little interchange between the entomological and optical research communities. Here, an overview is provided for all iridescence mechanisms observed in Coleoptera. Types of iridescence are illustrated and classified into three mechanistic groups: multilayer reflectors, three-dimensional photonic crystals and diffraction gratings. Taxonomic and phylogenetic distributions are provided, along with discussion of the putative functions and evolutionary pathways by which iridescence has repeatedly arisen in beetles.

Evolution of Insect Iridescence: Origins of Three-Dimensional Photonic Crystals in Weevils (Coleoptera: Curculionoidea).

A variety of photonic mechanisms give rise to iridescence and other structural colors in insects. In weevils (Coleoptera: Curculionoidea), iridescence is created by the most complex of these mechanisms, the three-dimensional photonic crystal. These self-assembling crystals take the form of triply periodic networks with single diamond or single gyroid symmetries and have been the subject of many descriptive studies based on individual species (often on a single specimen). To determine how these extraordinary nanostructures have evolved, we conduct the first comparative study of photonic crystals and setal nanostructure across Curculionoidea. By integrating structural data with newly available phylogenetic information, we demonstrate that-despite their widespread geographical and taxonomic distribution-three-dimensional photonic crystals appear to have evolved only once in weevils, in the common ancestor of a clade comprising the current subfamilies Entiminae and Cyclominae. Flattened, hollow setae with an unordered, spongy network in the lumen appear to be a necessary precursor to three-dimensional photonic crystals; we propose an evolutionary pathway by which this transformation has occurred.

Two new high altitude genera of Camiarini (Coleoptera: Leiodidae: Camiarinae) from Australia and New Zealand.

Two new leiodid genera and species, Camisolus ptinoides gen. nov., sp. nov. and Camiarodes nunni gen. nov., sp. nov. are described from southeastern Australia and New Zealand, respectively. Each new species is placed within its own genus on the basis of morphological uniqueness within Camiarini (Camiarinae) based on the presence of an enlarged maxillary palpomere 4 and metanepisternum with a lateral, tongue-like process that overlaps the elytron in repose. A key to the described genera is provided for world Camiarini. The tribe, new to Australia, is otherwise known only from New Zealand (six genera including one new) and southern South America (one genus). Both new genera are found exclusively in high altitude areas.

Reversible colour change in Arthropoda.

The mechanisms and functions of reversible colour change in arthropods are highly diverse despite, or perhaps due to, the presence of an exoskeleton. Physiological colour changes, which have been recorded in 90 arthropod species, are rapid and are the result of changes in the positioning of microstructures or pigments, or in the refractive index of layers in the integument. By contrast, morphological colour changes, documented in 31 species, involve the anabolism or catabolism of components (e.g. pigments) directly related to the observable colour. In this review we highlight the diversity of mechanisms by which reversible colour change occurs and the evolutionary context and diversity of arthropod taxa in which it has been observed. Further, we discuss the functions of reversible colour change so far proposed, review the limited behavioural and ecological data, and argue that the field requires phylogenetically controlled approaches to understanding the evolution of reversible colour change. Finally, we encourage biologists to explore new model systems for colour change and to engage scientists from other disciplines; continued cross-disciplinary collaboration is the most promising approach to this nexus of biology, physics, and chemistry.

Dual structural color mechanisms in a scarab beetle.

The cuticle of a Mycterophallus cetoniine scarab species displays both red iridescence due to a multilayer reflector mechanism and rainbow iridescence due to a superimposed diffraction grating mechanism. This is the first reported example of an animal possessing two independent classes of structural colors arising from interference at the wavelengths of visible light. In this work, the Mycterophallus cuticle is characterized by light microscopy, spectrophotometry, scanning electron microscopy, and transmission electron microscopy. We compare the cuticle of the Mycterophallus species to two closely related Lomaptera scarab species, one with only a multilayer reflector and the second with only a diffraction grating. We calculate the correspondence between the nanostructural parameters and the optical properties of the Mycterophallus cuticle to determine the relative optical contributions of the two color mechanisms and the interactions between them.