Ai-Ping Liang

Wetting properties on nanostructured surfaces of cicada wings

SUMMARY This study has investigated the wettability of forewings of 15 species of cicadas, with distinctly different wetting properties related to their nanostructures. The wing surfaces exhibited hydrophilic or weak to strong hydrophobic properties with contact angles ranging from 76.8 deg. to 146.0 deg. The nanostructures (protrusions), observed using environmental scanning electron microscopy (ESEM), were classified into four types according to the patterning, diameter (82–148 nm), spacing (44–117 nm) and height (159–446 nm). Surface analysis by X-ray photoelectron spectroscopy (XPS) showed significant differences in wing membrane chemistry. Thus, wetting properties at the macroscopic scale were dependent on slight differences in nanoscale architecture and composition of the wax layer. This investigation offers insights into the diversity of nanostructuring and how subtle small-scale changes may facilitate large changes in wettability.

A Molecular Phylogeny of Hemiptera Inferred from Mitochondrial Genome Sequences

Classically, Hemiptera is comprised of two suborders: Homoptera and Heteroptera. Homoptera includes Cicadomorpha, Fulgoromorpha and Sternorrhyncha. However, according to previous molecular phylogenetic studies based on 18S rDNA, Fulgoromorpha has a closer relationship to Heteroptera than to other hemipterans, leaving Homoptera as paraphyletic. Therefore, the position of Fulgoromorpha is important for studying phylogenetic structure of Hemiptera. We inferred the evolutionary affiliations of twenty-five superfamilies of Hemiptera using mitochondrial protein-coding genes and rRNAs. We sequenced three mitogenomes, from Pyrops candelaria, Lycorma delicatula and Ricania marginalis, representing two additional families in Fulgoromorpha. Pyrops and Lycorma are representatives of an additional major family Fulgoridae in Fulgoromorpha, whereas Ricania is a second representative of the highly derived clade Ricaniidae. The organization and size of these mitogenomes are similar to those of the sequenced fulgoroid species. Our consensus phylogeny of Hemiptera largely supported the relationships (((Fulgoromorpha,Sternorrhyncha),Cicadomorpha),Heteroptera), and thus supported the classic phylogeny of Hemiptera. Selection of optimal evolutionary models (exclusion and inclusion of two rRNA genes or of third codon positions of protein-coding genes) demonstrated that rapidly evolving and saturated sites should be removed from the analyses.

A new automatic identification system of insect images at the order level

A new automatic identification system has been designed to identify insect specimen images at the order level. Several relative features were designed according to the methods of digital image progressing, pattern recognition and the theory of taxonomy. Artificial neural networks (ANNs) and a support vector machine (SVM) are used as pattern recognition methods for the identification tests. During tests on nine common orders and sub-orders with an artificial neural network, the system performed with good stability and accuracy reached 93%. Results from tests using the support vector machine further improved accuracy. We also did tests on eight- and nine-orders with different features and based on these results we compare the advantages and disadvantages of our system and provide some advice for future research on insect image recognition.

Influence of cuticle nanostructuring on the wetting behaviour/states on cicada wings

The nanoscale protrusions of different morphologies on wing surfaces of four cicada species were examined under an environmental scanning electron microscope (ESEM). The water contact angles (CAs) of the wing surfaces were measured along with droplet adhesion values using a high-sensitivity microelectromechanical balance system. The water CA and adhesive force measurements obtained were found to relate to the nanostructuring differences of the four species. The adhesive forces in combination with the Cassie-Baxter and Wenzel approximations were used to predict wetting states of the insect wing cuticles. The more disordered and inhomogeneous surface of the species Leptopsalta bifuscata demonstrated a Wenzel type wetting state or an intermediate state of spreading and imbibition with a CA of 81.3° and high adhesive force of 149.5 µN. Three other species (Cryptotympana atrata, Meimuna opalifer and Aola bindusara) exhibited nanostructuring of the form of conically shaped protrusions, which were spherically capped. These surfaces presented a range of high adhesional values; however, the CAs were highly hydrophobic (C. atrata and A. bindusara) and in some cases close to superhydrophobic (M. opalifer). The wetting states of A. bindusara, C. atrata and M. opalifer (based on adhesion and CAs) are most likely represented by the transitional region between the Cassie-Baxter and Wenzel approximations to varying degrees.

A study of the anti-reflection efficiency of natural nano-arrays of varying sizes

The dependence of optical reflectivity and wettability on the surface topography of 32 species of cicada wing membranes has been investigated using UV-visible spectrophotometry, contact angle measurements and environmental scanning electron microscopy. The nanoscale hexagonally close packed protrusions have been shown to exhibit an anti-reflection and in some cases an anti-wetting function. The parameters of the structures were measured to be 77-148 nm in diameter, 44-117 nm in spacing and 159-481 nm in height. The transmittance spectrum and static contact angles were measured. At a wavelength range of 500-2500 nm, only minor differences in the anti-reflection performance were observed for each cicada species ascribed to the mechanism of impedance matching between cuticle and air. The transmittance properties of cicada wings were altered successfully through the scanning probe microscope-based manipulation by reducing the protrusion height via the contact mode. A near linear dependence was found between a decrease in protuberance height and a resulting increase in reflectance intensity. A diversity of wettability was observed with contact angles varying from 56.5° to 146.0°. Both effects of anti-reflection and wettability are dependent on the height of protrusions. The anti-reflection is insensitive when the wavelength is larger than the lateral feature size of the nanostructure. The stronger hydrophobic properties are generally associated with a larger diameter, closer spacing and greater height of protrusions when the wing membrane is intact.

The external male genitalia of Hemiptera (Homoptera — Heteroptera)

The morphology of the male genitalia has provided many useful characters for the systematics of Hemiptera. The genitalia and mating behaviour seem to have played crucial roles in the evolution of the Hemiptera. Although the literature on the male genitalic structures in Hemiptera is considerable, there has been very little attempt to compare the systems in the whole order. The present book provides a huge of morphological and anatomical data on the male genitalia of the Hemiptera. The book is divided into 11 sections in addition to an abstract. The section titles are: Introduction, Historical review, Techniques and methods, Acknowledgments, Terminology, Introductory account, Special morphology, Origin and evolution of structures, Discussion, Reference, and Appendix. Line illustrations of the male genitalia are provided for the following hemipteran groups and species: Aphidoidea (2 species), Coccoidea (5), Aleyrodoidea (1), Psylloidea (18), Cercopoidea (11), Cicadoidea (35), Membracoidea (including Cicadelloidea, 14 species), Fulgoroidea [432 species in 21 families: Tettigometridae (16), Caliscelidae (7), Hypochthonellidae (1), Gengidae (2), Eurybrachidae (1); Lophopidae (9), Ricaniidae (20), Tropiduchidae (21), Flatidae (26), Nogodinidae (14), Issidae (43), Acanaloniidae (3), Fulgoridae (31), Dictyopharidae (31), Kinnaridae (4), Meenoplidae (14), Delphacidae (66), Cixiidae (34), Derbidae (55), Achilidae (33) and Achilixiidae (1)], Coleorrhyncha (2) and Heteroptera (36). Obviously, the great part of this book is devoted to the Fulgoroidea, a group on which the authors have been working since 1980s. The brief discussions on the homologues of the male genitalic structures in different hemipteran groups and on the origin and evolution of the male genitalia in the order will be interesting to hemipterists. Several novelties on Fulgoroidea in the book should be noted. The Caliscelidae was formally given a family rank which includes Caliscelini and Augilini although no synapomorphies shared by the two tribes were found in the phylogenetic analysis in the book. A new familiar relationship hypothesis in the Fulgoroidea is proposed in the appendix based on the male genitalic characters and other morphological characters, with (Cicadoidea + Cercopoidea) + Membracoidea as outgroups: Tettigometridae + (Augilini + Caliscelini + «Hypochthonellidae + Gengidae) + «(Eurybrachidae + Lophopidae + Ricaniidae) + (Tropiduchidae + (Flatidae + Nogodinidae + Issidae + Acanaloniidae))) + «Fulgoridae + Dictyopharidae) + «Kinnaridae + Meenoplidae) + Delphacidae) + «Cixiidae + Derbidae) + (Achilidae + Achilixiidae)))))). This differs from the hypothesis advocated by Emeljanov (1990) and also contradicts with the current opinions that the Fulgoroidea is the sister group of the Heteroptera + Coleorrhyncha and that the traditional Auchenorrhyncha and Homoptera are both paraphyletic. For those who work on the Hemiptera, this book is a must. However, the readers should be aware of the many old specific combinations used in the book.

Complete Mitochondrial Genome of the Small Brown Planthopper, Laodelphax striatellus (Delphacidae: Hemiptera), with a Novel Gene Order

We determined the first complete mitochondrial genome (mitogenome) sequence from a representative of the insect family Delphacidae, Laodelphax striatellus. The 16,513 bp long L. striatellus mitogenome encodes 13 putative proteins, two ribosomal RNAs, and 22 transfer RNAs, and contains a putative control region (or A+T-rich region). The nucleotide composition is biased toward adenine and thymine (77.2% A+T), and the amino acid composition is affected to a similar degree by the AT mutational bias. All 13 protein-coding genes (PCGs) start with a typical ATN initiation codon. Eight of 13 PCGs in L. striatellus have a complete termination codon (TAA), whereas the remaining five have incomplete termination codons. The anticodons of the L. striatellus tRNAs are identical to those in Drosophila yakuba, and all tRNAs except for tRNASer-AGN can be folded in the form of a typical cloverleaf structure. The A+T-rich region of L. striatellus was found between srRNA and tRNAlle, and the entire region was 2040 bp long. The gene content of the L. striatellus mitogenome is identical to other completely sequenced insect mitogenomes, while the gene order is different from the common arrangement found in most insects: five tRNA genes and three PCGs in the L. striatellus mitogenome have changed positions relative to the ancestral arrangement of mitochondrial genes in D. yakuba. Besides describing the above contents, we also aligned the mitogenome sequence of L. striatellus with other hemipterans to analyse the phylogenetic relationships of Hemiptera. The results show that Heteroptera is the sister group to all other Hemiptera, and Cicadomorpha is the sister group to the clade Fulgoromorpha+Sternorrhyncha.

The complete mitochondrial genome sequence of the planthopper, Sivaloka damnosus.

Abstract The complete mitochondrial genome (mitogenome) sequence was determined from the plant hopper, Sivaloka damnosus Chow and Lu (Hemiptera: Issidae), a representative of the insect family Issidae. The genome is a circular molecule of 15,287 bp with a total A+T content of 76.5%. The gene content, order, and structure are identical to that in Drosophila melanogaster, which is considered ancestral for insects. All 13 protein-coding genes of the S. damnosus mitogenome have a putative inframe ATR methionine or ATT isoleucine codons as start signals. The usual termination codons (TAA and TAG) were found in 11 protein-coding genes. However, atp6, and nad4 have incomplete termination codons. All tRNAs show stable canonical clover-leaf structures similar to other insect mitochondrial tRNAs, except for tRNASer(AGN), which has a reduced DHU arm. The A+T-rich region or putative control region includes two extensive repeat regions. The first repeat region is composed of two sets of complicated repeat units, and these repetitive sequences are arranged alternately; the second contains ten 20 bp tandemly repetitive sequences. In the phylogenetic analyses based on protein-coding genes, Cicadomorpha is a sister to Fulgoromorpha+Sternorrhyncha, and Heteroptera is a sister to all other Hemiptera.

New taxa and revisionary notes in Rhinaulacini spittlebugs from southern Asia (Homoptera: Cercopidae)

A checklist of all Rhinaulacini (Auchenorrhyncha: Cercopidae) from southern Asia is given, together with a key for all the genera, new distributional records, and keys and figures of the species of Sounama, Kanozata and Circulocercopis gen. nov. New taxa are described and taxonomic changes proposed (see ‘Summary of proposed taxonomic changes’). Scanning electron micrographs of the head and antennal sensilla of the male adult of Sounama (Stenaulophrys) borneensis are provided.

A Preliminary Molecular Phylogeny of Planthoppers (Hemiptera: Fulgoroidea) Based on Nuclear and Mitochondrial DNA Sequences

The planthopper superfamily Fulgoroidea (Insecta: Hemiptera) is one of the most dominant groups of phytophagous insects. It comprises about 20 families, containing a total of 9000 species worldwide. Despite several recent studies, the phylogeny of Fulgoroidea is not yet satisfactorily resolved and the phylogenetic positions of several key families, especially Cixiidae, Delphacidae, Tettigometridae, Nogodinidae, Acanaloniidae and Issidae, are contentious. Here, we expand upon recent phylogenetic work using additional nuclear (18S and 28S) and novel mitochondrial (16S and cytb) markers. Maximum likelihood and Bayesian analyses yielded robust phylogenetic trees. In these topologies, a group containing Cixiidae and Delphacidae is recovered as the sister group to the remaining taxa. Tettigometridae is placed in a more nested position and is grouped with Caliscelidae. Sister relationships are found between Flatidae and Ricaniidae, and between Dictyopharidae and Fulgoridae. Nogodinidae and Issidae are confirmed to be non-monophyletic families. For major nodes of interest, divergence date estimates are generally older than those from the fossil record.