Temperature Evolution of Composition, Thermal, Electrical and Magnetic Properties of Ti3C2Tx-MXene.

MXenes are a family of two-dimensional nanomaterials. Titanium carbide MXene (Ti3C2Tx-MXene), reported in 2011, is the first inorganic compound reported among the MXene family. In the present work, we report on the study of the composition and various physical properties of Ti3C2Tx-MXene nanomaterial, as well as their temperature evolution, to consider MXenes for space applications. X-ray diffraction, thermal analysis and mass spectroscopy measurements confirmed the structure and terminating groups of the MXene surface, revealing a predominant single OH layer character. The temperature dependence of the specific heat shows a Debye-like character in the measured range of 2 K-300 K with a linear part below 10 K, characteristic of conduction electrons of metallic materials. The electron density of states (DOS) calculations for Ti3C2OH-MXene reveal a significant DOS value at the Fermi level, with a large slope, confirming its metallic character, which is consistent with the experimental findings. The temperature dependence of electrical resistivity of the MXene samples was tested for a wide temperature range (3 K-350 K) and shows a decrease on lowering temperature with an upturn at low temperatures, where negative magnetoresistance is observed. The magnetoresistance versus field is approximately linear and increases its magnitude with decreasing temperature. The magnetization curves are straight lines with temperature-independent positive slopes, indicating Pauli paramagnetism due to conduction electrons.

Inconsistencies in the Classification of the Family Cydnidae (Hemiptera: Heteroptera: Pentatomoidea) Revealed by Molecular Apomorphies in the Secondary and Tertiary Structures of 18S rRNA Length-Variable Region L (LVR L).

The SSU nuclear rDNA (encoding 18S ribosomal RNA) is one of the most frequently sequenced genes in the molecular analysis of insects. Molecular apomorphies in the secondary and tertiary structures of several 18S rRNA length-variable regions (LVRs) located within the V2, V4, and V7 hypervariable regions can be good indicators for recovering monophyletic groups within some heteropteran families. Among the LVRs that have been analysed, the LVR L in the V4 hypervariable region is the longest and most crucial for such assessments. We analysed the 18S rRNA V4 hypervariable region sequences of 45 species from the family Cydnidae, including all 6 subfamilies (Amaurocorinae, Amnestinae, Cephalocteinae, Cydninae, Garsauriinae, and Sehirinae) and three pentatomoid families (Parastrachiidae, Thaumastellidae, and Thyreocoridae), which have often been included in the broadly defined Cydnidae family. This is the first time that representatives of all Cydnidae subfamilies have been included in a molecular analysis. Only taxa from two subfamilies, Sehirinae and Cydninae, have been used in previous molecular studies. The secondary and tertiary structures of the LVR L were predicted for each species using the two-step procedure already accepted for such analyses to recover any molecular apomorphy essential for determining monophyly. The results of our comparative studies contradict the current understanding of the relationships among burrowing bugs and the current family classification.

Tribe Acalyptaini (Hemiptera: Tingidae: Tinginae) Revisited: Can Apomorphies in Secondary and Tertiary Structures of 18S rRNA Length-Variable Regions (LVRs) Support Tribe Validity?

The lace bug tribe Acalyptaini (Tingidae: Tinginae) includes five genera, Acalypta, Derephysia, Dictyonota, Kalama, and Recaredus, and it was recently resurrected based on morphological and karyological characters. We aimed to validate the distinctiveness of this tribe using 18S rDNA sequences, which have not been used in previous Tingidae phylogenomic studies. Our results confirmed the monophyly of the tribe. Moreover, the monophyly of the subfamily Cantacaderinae and its basal position within the family Tingidae were indicated, as well as the position of the tribe Litadeini as sister to all other Tinginae. In addition, we attempted to determine the apomorphic morpho-molecular characters in the secondary and tertiary structures of length-variable regions of the 18S rRNA sequences of the analysed species. The results showed that two LVRs (LVR X and LVR L) of the hypervariable region V4 exhibited significant variability in the number of nucleotides and could be considered for apomorphic recognition.

Molecular Apomorphies in the Secondary and Tertiary Structures of Length-Variable Regions (LVRs) of 18S rRNA Shed Light on the Systematic Position of the Family Thaumastellidae (Hemiptera: Heteroptera: Pentatomoidea).

The SSU nrDNA, a small subunit of the nuclear ribosomal DNA (coding 18S rRNA), is one of the most frequently sequenced genes in molecular studies in Hexapoda. In insects, including true bugs (Hemiptera: Heteroptera), only its primary structures (i.e., aligned sequences) are predominantly used in phylogenetic reconstructions. It is known that including RNA secondary structures in the alignment procedure is essential for improving accuracy and robustness in phylogenetic tree reconstruction. Moreover, local plasticity in rRNAs might impact their tertiary structures and corresponding functions. To determine the systematic position of Thaumastellidae within the superfamily Pentatomoidea, the secondary and-for the first time among all Hexapoda-tertiary structures of 18S rRNAs in twelve pentatomoid families were compared and analysed. Results indicate that the shapes of the secondary and tertiary structures of the length-variable regions (LVRs) in the 18S rRNA are phylogenetically highly informative. Based on these results, it is suggested that the Thaumastellidae is maintained as an independent family within the superfamily Pentatomoidea, rather than as a part of the family Cydnidae. Moreover, the analyses indicate a close relationship between Sehirinae and Parastrachiidae, expressed in morpho-molecular synapomorphies in the predicted secondary and tertiary structures of the length-variable region L (LVR L).

One Species, Hundreds of Subspecies? New Insight into the Intraspecific Classification of the Old World Swallowtail (Papilio machaon Linnaeus, 1758) Based on Two Mitochondrial DNA Markers.

The Old World swallowtail Papilio machaon Linnaeus, 1758 is one of the most well-known and most characteristic members of the family Papilionidae. Over the past two centuries, the butterfly has been the subject of many studies. P. machaon is characterised by a tendency to change the wing colour pattern. In turn, due to the great interest of collectors and amateur entomologists, these studies have been converted into the description of over 100 colour forms, aberrations and subspecies. In this study, mitochondrial DNA (mtDNA), 16S rDNA and cytochrome b sequences were used to examine the correlation between the intraspecific classification and genetic structure of P. machaon. The study used 87 specimens from 59 different localities covering the geographic distribution of this species in the Palaearctic. The phylogenetic relationships within and between the Old World swallowtail subspecies showed that the intraspecific classification proposed by various authors does not correlate with the variability in mitochondrial DNA sequences. In addition, populations occurring at the species distribution borders in the Palaearctic Region (i.e., Japan, Kamchatka, Morocco and Sakhalin) are genetically distinct from other species.

The King's Lace Bug Recaredus rex Distant, 1909 (Hemiptera: Heteroptera: Tingidae): Systematic Position, First Palaearctic and Afrotropical Records, and Ecological Niche Modelling.

The systematic position and actual distribution of Recaredus rex, for a long time one of the most enigmatic lace bug genus and species, is very obscure because only the type specimen and three other individuals from India are known to date. In the present paper, we report the first records of R. rex from the Palaearctic region (Iran) and tropical Africa (Ghana). Based on the occurrence localities and climatic variables, we predict potentially useful ecological niches for this species using Maxent software. The areas with the best environmental conditions for R. rex indicated in our studies suggest its possible Palaeotropical distribution. Moreover, we regard these results as a good starting point for further searches for specimens of this species. This might help verify the hypothesis of the broad Palaeotropical distribution of R. rex and its oligo- or polyphagy. In addition, the lace bug genus Recaredus, based on the diagnostic characteristics provided for the tribe Acalyptaini, and the structure of aedeagus, is transferred from the tribe Ypsotingini to the Acalyptaini. A key to all genera currently included in the latter tribe is also provided.

Geotomus granulosus, a peculiar sehirine-like new species of the subfamily Cydninae (Hemiptera: Heteroptera: Cydnidae) from Burundi.

Geotomus granulosus sp. n. is described from Burundi, and is the third burrower bug species recorded hitherto from this country. This burrower bug resembles species of two Sehirinae genera, i.e. Ochetostethus Fieber, 1860 and Ochetostethomorpha Schumacher, 1913, in its dorsal body habitus. However, all its crucial diagnostic characters (the body chaetotaxy, the shape of evaporatoria and the peritreme, the meso- and metathoracic wings venation, and the shape of spermatheca) demonstrate it represents the genus Geotomus Mulsant et Rey, 1866 (subfamily Cydninae, tribe Geotomini sensu lato).

Systematic Position of the Fossil Burrower Bug Eocenocydnus lisi Popov, 2019 (Hemiptera, Heteroptera, Cydnidae) Revealed by a Parallel/Cross-Eyed Viewing Method Used for Obtaining Three-Dimensional Images.

The fossil burrower bug Eocenocydnus lisi described from the Late Eocene of the Isle of Wight, UK, is analysed using a parallel, cross-eyed viewing method. The species, tentatively placed in the subfamily Sehirinae, is redescribed and its systematic position is discussed. Newly recovered morphological characteristics allow it to be placed in the tribe Cydnini of the subfamily Cydninae.

Structure, Morphology, Heat Capacity, and Electrical Transport Properties of Ti3(Al,Si)C2 Materials.

A study of Ti3Al1-xSixC2 (x = 0 to x = 1) MAX-phase alloys is reported. The materials were obtained from mixtures of Ti3AlC2 and Ti3SiC2 powders with hot pressing sintering technique. They were characterised with X-ray diffraction, heat capacity, electrical resistivity, and magnetoresistance measurements. The results show a good quality crystal structure and metallic properties with high residual resistivity. The resistivity weakly varies with Si doping and shows a small, positive magnetoresistance effect. The magnetoresistance exhibits a quadratic dependence on the magnetic field, which indicates a dominant contribution from open electronic orbits. The Debye temperatures and Sommerfeld coefficient values derived from specific heat data show slight variations with Si content, with decreasing tendency for the former and an increase for the latter. Experimental results were supported by band structure calculations whose results are consistent with the experiment concerning specific heat, resistivity, and magnetoresistance measurements. In particular, they reveal that of the s-electrons at the Fermi level, those of Al and Si have prevailing density of states and, thus predominantly contribute to the metallic conductivity. This also shows that the high residual resistivity of the materials studied is an intrinsic effect, not due to defects of the crystal structure.

Ammianus pericarti sp. n. (Hemiptera: Heteroptera: Tingidae), the first strictly Palaearctic representative of the genus with a key to the species of the Ammianus junodi group.

Ammianus pericarti sp. n., the first strictly Palaearctic representative of the genus, is described from Agadir (Morocco) as new to the science. The species is illustrated and compared to all its morphologically similar representatives of the Ammianus junodi group; a key to this species group is also provided. Moreover, A. vanderijsti (Schouteden, 1923) is reported for the first time from the Republic of South Africa.

emHypsipyrgias/em emjoseliae/em, a new species of lace bugs (Heteroptera: Tingidae: Tinginae) from New Guinea with a key to species of the genus emHypsipyrgias/em, and comments on three allied genera emHypsipyrgias/em Kirkaldy, 1908, emDiplocysta/em Horváth, 1925, and Hypsotingis Drake, 1960.

Hypsipyrgias joseliae sp. n. (Heteroptera: Tingidae: Tinginae) from New Guinea is described, illustrated and compared with its two relatives, namely H. telamonides Kirkaldy, 1908 from Australia, and H. euphues Drake and Ruhoff, 1962 from Lord Howe Island. Key to species of the genus Hypsipyrgias is also provided. Two genera very closely related to Hypsipyrgias Kirkaldy, 1908, namely Hypsotingis Drake, 1960 and Diplocysta Horváth, 1925 are re-diagnosed. Diplocysta globuliformis Hacker, 1928, D. papuana Drake, 1960, D. rustica, Drake, 1960 and D. thaleia Drake and Ruhoff, 1965 are transferred from Diplocysta to Hypsotingis.

Megymenum tuberculatum, a new species of Megymenini from Java and a review of distribution of M. brevicorne (Hemiptera: Heteroptera: Dinidoridae).

Megymenum tuberculatum Hemala Kocorek, sp. nov. (Hemiptera: Heteroptera: Dinidoridae: Megymeninae: Megymenini) from Java (Indonesia) is described, illustrated and compared with M. brevicorne (Fabricius, 1787). Although the description is based on only one female specimen, the differences in the morphology of head, pronotum, and spermatheca are significant. In addition, M. brevicorne is briefly redescribed and its distribution and biology reviewed along with its first record from Nepal.

Another alien bug in Europe: the first case of transcontinental introduction of the Asiatic burrower bug Macroscytus subaeneus (Dallas, 1851) (Hemiptera: Heteroptera: Cydnidae) to the U.K. through maritime transport.

The Oriental burrower bug Macroscytus subaeneus (Dallas, 1851) (Hemiptera: Heteroptera: Cydnidae: Cydninae), presently known only from single localities in Flores (Indonesia), the Philippines and Thailand, is recorded from the United Kingdom (hereafter U.K.). A single female specimen was collected on the semi-rural edge of Bath city by a Starling (Sturnus vulgaris L.) and taken to its nest from which it was retrieved during 2015. The specimen is illustrated and its diagnostic characters are provided. We hypothesize that this specimen could have been imported with a shipping container from Thailand.

Notes on Afrotropical Cydnidae (Heteroptera) with emphasis on vehicle-mounted net samples and description of a new species from Liberia, West Africa.

Notes on the Cydnidae fauna in Liberia, sampled with a vehicle-mounted net, the species taxonomy and general distribution are reported, including the description of Chilocoris elongatus sp. nov. In addition, new country records are provided for Angola, Ethiopia, Gabon, Guine    a-Bissau, Namibia, Niger, Republic of South Africa, Sierra Leone, Tanzania, Togo, Uganda, and Zimbabwe.

Chilocoris capensis n. sp., the first species of the genus Chilocoris Mayr, 1865 (Hemiptera: Heteroptera: Cydnidae) recorded in the Republic of South Africa with an annotated checklist of South African burrower bugs.

Chilocoris capensis n. sp. collected from fallen ripe figs of broom cluster fig Ficus sur Forsskål, 1775, the first burrower bug species of the genus Chilocoris Mayr, 1865 recorded in the Republic of South Africa, is described and compared with Chilocoris laevicollis Horváth, 1919, the morphologically most closely allied Afrotropical species. Additionally, an annotated checklist of burrower bug species recorded in the Republic of South Africa is provided. The known biology of Afrotropical Chilocoris species is briefly summarized.

Chilocoris serratus n. sp., the first burrower bug species (Hemiptera: Heteroptera: Cydnidae) recorded in Guinea-Bissau with an annotated checklist of the Afrotropical species of the genus Chilocoris Mayr, 1865.

The first burrower bug species recorded in Guinea-Bissau, Chilocoris serratus n. sp., is described and compared with morphologically related species. Additionally, an annotated checklist of Afrotropical species of the genus Chilocoris is provided.

In BOLD we trust? A commentary on the reliability of specimen identification for DNA barcoding: a case study on burrower bugs (Hemiptera: Heteroptera: Cydnidae).

An assessment was performed regarding the accuracy of various types of data deposited in the Barcode of Life Data system (BOLD) related to the true bug family Cydnidae (Hemiptera: Heteroptera). Taxonomic nomenclature and classification, identification reliability, and the correctness of the data provided in the "Taxon description" were analyzed and commented on with respect to both available versions of the BOLD system, i.e. version 3 and beta version 4. Numerous mistakes in taxonomy, the relevance of the taxa names, and species misidentifications in BOLD version 3 were found and, more importantly, similar errors were detected in BOLD version 4 as well. We suggest that if the BOLD system is presumed to be taxonomically trustworthy, it can't exist without an adequate a priori identification of barcoded specimens. Otherwise, the erroneous data deposited onto the BOLD platform will have a negative impact on studies in which molecular data imported from BOLD are utilized.

Chilocoris laevicollis Horváth, 1919, and Ch. umbricola Linnavuori, 1993-two trogloxenic burrower bugs recorded for the first time in Gabon (Central Africa).

First country records of two burrower bugs, Chilocoris laevicollis, and Ch. umbricola (Hemiptera: Heteroptera: Cydnidae) from Gabon (Central Africa) are presented. The study was based on the specimens collected by Dr. V. Aellen, a well-known Swiss speleologist, taken from two caves near Lastoursville in the Gabonese Republic. Diagnostic characters for both recorded species are provided, and data on their biology and distribution are summarized.

Amnestus mendeli sp. n., the first burrower bug species (Hemiptera: Heteroptera: Cydnidae) recorded on Ascension Island, central Atlantic Ocean.

A new species of the genus Amnestus Dallas, 1851, Amnestus mendeli, is described from the cloud zone of Green Mountain, Ascension Island, and compared with its closest relatives, the Brazilian Amnestus lenkoi Froeschner, 1975 and Amnestus pequinus Froeschner, 1975. It is the first representative of the family Cydnidae recorded on the island thus far. The species is presumed to be an introduction from the Americas, but the hypothesis that it might be endemic to Ascension Island is also not excluded.