Morphometric and molecular discrimination of the sugarcane aphid, Melanaphis sacchari, (Zehntner, 1897) and the sorghum aphid Melanaphis sorghi (Theobald, 1904).

Melanaphis sacchari (Zehntner, 1897) and Melanaphis sorghi (Theobald, 1904) are major worldwide crop pests causing direct feeding damage on sorghum and transmitting viruses to sugarcane. It is common in the scientific literature to consider these two species as synonyms, referred to as the 'sugarcane aphid', although no formal study has validated this synonymy. In this study, based on the comparison of samples collected from their whole distribution area, we use both morphometric and molecular data to better characterize the discrimination between M. sacchari and M. sorghi. An unsupervised multivariate analysis of morphometric data clearly confirmed the separation of the two species. The best discriminating characters separating these species were length of the antenna processus terminalis relative to length of hind tibia, siphunculus or cauda. However, those criteria sometimes do not allow an unambiguous identification. Bayesian clustering based on microsatellite data delimited two clusters, which corresponded to the morphological species separation. The DNA sequencing of three nuclear and three mitochondrial regions revealed slight divergence between species. In particular, the COI barcode region proved to be uninformative for species separation because one haplotype is shared by both species. In contrast, one SNP located on the nuclear EF1-α gene was diagnostic for species separation. Based on morphological and molecular evidence, the invasive genotype damaging to sorghum in the US, Mexico and the Caribbean since 2013 is found to be M. sorghi.

Tuberocephalus tsengi (Tao, 1963) STAT. REV. (Hemiptera: Aphididae), an East Asian Artemisia-feeding aphid species introduced to Britain.

Tuberocephalus tsengi (Tao, 1963) STAT. REV., an aphid species described from China, is reported feeding on Artemisia vulgaris in southern England. This species is here redescribed and distinguished from T. sasakii (Matsumura, 1917), with which it has previously been synonymised.

Catalog of the phylloxerids of the world (Hemiptera, Phylloxeridae).

A taxonomic and nomenclatural catalog of the phylloxerids (Hemiptera, Phylloxeridae) is presented. Six family-group names are listed, three being synonyms. Thirty-five genus-group names, of which six are subjectively valid, are presented with their type species, etymology, and grammatical gender. Ninety-four species-group names are listed, of which 73 are considered subjectively valid. This is the last group of Aphidomorpha to be catalogued, bringing the list of valid extant species to 5,218.

A new species of Aphis Linnaeus (Hemiptera, Aphididae) living on Teucrium polium L. (Lamiaceae).

Aphis polii sp. n. living on Teucrium polium L. (Lamiaceae) is described, based on apterous and alate viviparous females and oviparous females. It has been collected from seventeen localities in mainland France, Corsica, Italy, Ukraine, Lebanon and Iran. The new species is similar to two other Aphis species that feed specifically on plants of the genus Teucrium, but has a relatively longer ultimate rostral segment. Characters are provided to discriminate between the three Teucrium-feeding species, and to distinguish the new species from other morphologically similar Aphis species that feed on Lamiaceae. Type specimens are deposited in the Muséum national d'Histoire naturelle, Paris, France (MNHN), the UMR Centre de Biologie pour la Gestion des Populations, Montpellier, France and the Natural History Museum, London, UK (BMNH).

The cytogenetic architecture of the aphid genome.

In recent years aphids, with their well-defined polyphenism, have become favoured as model organisms for the study of epigenetic processes. The availability of the pea aphid (Acyrthosiphon pisum) genome sequence has engendered much research aimed at elucidating the mechanisms by which the phenotypic plasticity of aphids is inherited and controlled. Yet so far this research effort has paid little attention to the cytogenetic processes that play a vital part in the organisation, expression and inheritance of the aphid genome. Aphids have holocentric chromosomes, which have very different properties from the chromosomes with localised centromeres that are found in most other organisms. Here we review the diverse forms of aphid chromosome behaviour that occur during sex determination and male and female meiosis, often in response to environmental changes and mediated by endocrine factors. Remarkable differences occur, even between related species, that could have significant effects on the inheritance of all or parts of the genome. In relation to this, we review the particular features of the distribution of heterochromatin, rDNA genes and other repetitive DNA in aphid chromosomes, and discuss the part that these may play in the epigenetic modification of chromatin structure and function.

Two more new species of Aphidura (Hemiptera, Aphididae), and a note on variation in Aphidura bozhkoae Narzikulov.

Two new species of Aphidura Hille Ris Lambers, 1956 (Hemiptera, Aphididae, Macrosiphini) are described; Aphidura libanensis sp. n. from Prunus prostrata in Lebanon, and Aphidura corsicensis sp. n. from Cerastium soleirolii in Corsica (France). Studies of Aphidura bozhkoae specimens from different localities have revealed that this species varies in its pattern of dorsal sclerotisation and other morphological characters, within and between populations. An updated key for identifying the world's species of Aphidura is presented.

Identity of Schizaphis species (Hemiptera: Aphididae) in the United Kingdom: are they a threat to crops?

The greenbug, Schizaphis graminum (Rondani), is a major pest of cereals in some parts of the world and is of particular concern because it can be resistant to some insecticides and overcome the resistance of crops. In the UK, it has never been found on crops, but two rather little-known and closely-related species (Schizaphis holci and Schizaphis agrostis) are associated with the wild grasses, Holcus lanatus and Agrostis stolonifera. Since 1987, winged (alate) aphids morphologically resembling the greenbug have been found in increasing numbers in 12.2 m high suction-trap samples of the Rothamsted Insect Survey (RIS); hence, studies were undertaken to establish their identity. Clones (=asexual lineages) established from populations collected from H. lanatus in southern England showed strong preference for Holcus over Agrostis and Hordeum in laboratory tests and produced sexual morphs when transferred to short-day conditions, the males being apterous, as expected for S. holci. Multivariate morphometric comparisons of alatae caught in UK RIS suction traps in 2007 and 2011 with named specimens from museum collections, including S. graminum from many countries, indicated that the suction-trapped alatae were mostly S. agrostis and S. holci. Cytochrome c oxidase subunit I (COI) mtDNA obtained from 62 UK specimens from suction-traps had 95.4-100% sequence identity with US specimens of S. graminum. Two of the UK specimens had identical COI sequence to the US sorghum-adapted form of S. graminum, and these specimens also had 100% identity with a 640 bp fragment of nDNA CytC, indicating that this form of S. graminum may already be present in the UK. Present and future economic implications of these results are discussed.

Karyotype variation in the South American aphid genus Neuquenaphis (Hemiptera, Aphididae, Neuquenaphidinae).

The endemic South American aphid genus Neuquenaphis (Hemiptera, Aphididae, Neuquenaphidinae) forms an important component of the phytophagous insect fauna associated with southern beeches, Nothofagus (Nothofagaceae), but has not previously been studied cytologically. As part of ongoing studies of the taxonomy, evolution and host relationships of this genus, the karyotypes of 12 species are described and illustrated. Species are mostly distinguishable by differences in number and/or relative lengths of chromosomes, with 2n (female) numbers ranging from 6 to 16. The taxonomic and evolutionary significance of the karyotype variation in this group are discussed.