Checklist of the dragonflies and damselflies (Insecta: Odonata) of Bangladesh, Bhutan, India, Nepal, Pakistan and Sri Lanka.

A checklist of the dragonflies and damselflies occurring in Bangladesh, Bhutan, India (including Andaman and Nicobar Islands), Nepal, Pakistan and Sri Lanka is presented. In total 588 (including 559 full species) taxa are known to occur in the region of which 251 taxa (species subspecies) are single country endemics. Recent taxonomic changes relevant to the area are summarized. Sixteen taxa are synonymized and a checklist of all synonyms established since 1950 is provided. Information is given on available larval descriptions including a list of genera present in the region for which no larvae have yet been described. Numerous species occurring in the area are still poorly known and a list of genera for which a revision is urgently needed is provided.                The following new synonyms are established: Calicnemia sudhaae Mitra, 1994 = Calicnemia imitans Lieftinck, 1948 syn. nov.; Ceriagrion fallax cerinomelas Lieftinck, 1927 = Ceriagrion fallax Ris, 1914 syn. nov.; Ceriagrion fallax pendleburyi Laidlaw, 1931 = Ceriagrion fallax Ris, 1914 syn. nov.; Coenagrion kashmirus Chowdhary Das, 1975 = Ischnura forcipata Morton, 1907 syn. nov.; Enallagma insula Fraser, 1920 = Aciagrion occidentale Laidlaw, 1919 syn. nov.; Himalagrion pithoragarhicum Sahni, 1964 = Ceriagrion fallax Ris, 1914 syn. nov.; Ischnura bhimtalensis Sahni, 1965 = Ischnura rubilio Selys, 1876 syn. nov.; Onychargia indica Sahni, 1964 = Paracercion calamorum (Ris, 1916) syn. nov.; Anaciaeschna kashmirense Singh Baijal, 1954 = Anaciaeschna martini (Selys, 1897) syn. nov.; Cyclogomphus vesiculosus Selys, 1854 = Cyclogomphus ypsilon Selys, 1954 syn. nov.; Chlorogomphus brittoi Navás, 1934 = Chlorogomphus xanthoptera (Fraser, 1919) syn. nov.; Hylaeothemis indica Fraser, 1946 = Hylaeothemis apicalis Fraser, 1924 syn. nov.; Sympetrum durum Bartenef, 1916 = Sympetrum striolatum commixtum Selys, 1884 syn. nov.; Sympetrum himalayanum Navás, 1934 = Sympetrum hypomelas (Selys, 1884) syn. nov.; Sympetrum haematoneura Fraser, 1924 = Sympetrum speciosum Oguma, 1915 syn. nov.; Sympetrum speciosum taiwanum Asahina, 1951 = Sympetrum speciosum Oguma, 1915 syn. nov.                In addition, Periaeschna lebasi Navás, 1930 is regarded a nomen nudum. The following new combinations are proposed: Onychogomphus acinaces Laidlaw, 1922 is transferred to the genus Melligomphus Chao, 1990 resulting in Melligomphus acinaces (Laidlaw, 1922) comb. nov. Onychogomphus saundersii Selys, 1854 is transferred to the genus Nychogomphus Carle, 1986 resulting in Nychogomphus saundersii (Selys, 1854) comb. nov..

Covert linear polarization signatures from brilliant white two-dimensional disordered wing structures of the phoenix damselfly.

The damselfly Pseudolestes mirabilis reflects brilliant white on the ventral side of its hindwings and a copper-gold colour on the dorsal side. Unlike many previous investigations of odonate wings, in which colour appearances arise either from multilayer interference or from wing-membrane pigmentation, the whiteness on the wings of P. mirabilis results from light scattered by a specialized arrangement of flattened waxy fibres and the copper-gold colour is produced by pigment-based filtering of this light scatter. The waxy fibres responsible for this optical signature effectively form a structure that is disordered in two dimensions and this also gives rise to distinct optical linear polarization. It is a structure that provides a mechanism enabling P. mirabilis to display its bright wing colours efficiently for territorial signalling, both passively while perched, in which the sunlit copper-gold upperside is presented against a highly contrasting background of foliage, and actively in territorial contests in which the white underside is also presented. It also offers a template for biomimetic high-intensity broadband reflectors that have a pronounced polarization signature.

Honouring His Royal Highness the Crown Prince of Bhutan: Megalestes gyalsey (Odonata: Synlestidae).

Megalestes gyalsey spec. nov. is described from a single male from Trongsa District in Bhutan. The species was discovered during field work conducted in 2015 for the Bhutan invertebrate biodiversity project. The species is named in honour of His Royal Highness Crown Prince Jigme Namgyel Wangchuck, the Gyalsey of Bhutan, on the occasion of his first birthday.

Two new species of Papuagrion Ris, 1913 (Odonata: Coenagrionidae) from New Guinea with a survey of distribution records for the genus.

Two new species of Papuagrion Ris, 1913 are described from Papua Province, Indonesia. These are P. marirobi sp .nov. from Japen Island and P. stellimontanum sp .nov., from the Star Mountains. The new species are, respectively, most closely allied to P. degeneratum Lieftinck and P. digitiferum Lieftinck. They bring the number of Papuagrion species to 28. New locality records of several other species are noted.

Three new species of Papuagrion Ris, 1913 (Odonata: Coenagrionidae) from the Hindenburg Wall region of western Papua New Guinea.

Three distinctive new species of Papuagrion Ris, 1913 are described from a high altitude area (1,770-1,820 m a.s.l.) at the base of the Hindenburg Wall, Western Province, Papua New Guinea. These are P. chrysosoma sp. nov., P marijanmatoki sp. nov. and P. tydecksjuerging sp. nov.; all type material is deposited in the South Australian Museum (SAMA). These were the only species of the genus collected at higher altitudes in the Ok Tedi headwaters, and none of them were encountered at lower altitudes (300-900 m) despite intensive searches there. The new species described here bring to 26 the number of Papuagrion species known from the New Guinea region.

Wrinkles enhance the diffuse reflection from the dragonfly Rhyothemis resplendens.

The dorsal surfaces of the hindwings of the dragonfly Rhyothemis resplendens (Odonata: Libellulidae) reflect a deep blue from the multilayer structure in its wing membrane. The layers within this structure are not flat, but distinctly 'wrinkled', with a thickness of several hundred nanometres and interwrinkle crest distances of 5 µm and greater. A comparison between the backscattered light from R. resplendens and a similar, but un-'wrinkled' multilayer in the damselfly Matronoides cyaneipennis (Odonata: Calopterygidae) shows that the angle over which incident light is backscattered is increased by the wrinkling in the R. resplendens structure. Whereas the reflection from the flat multilayer of M. cyaneipennis is effectively specular, the reflection from the wrinkled R. resplendens multilayer spans 1.47 steradians (equivalent to ±40° for all azimuthal angles). This property enhances the visibility of the static wing over a broader angle range than is normally associated with a smooth multilayer, thereby markedly increasing its conspicuousness.

Subtle design changes control the difference in colour reflection from the dorsal and ventral wing-membrane surfaces of the damselfly Matronoides cyaneipennis.

The hind wings of males of the damselfly Matronoides cyaneipennis exhibit iridescence that is blue dorsally and green ventrally. These structures are used semiotically in agonistic and courtship display. Transmission electron microscopy reveals these colours are due to two near-identical 5-layer distributed Bragg reflectors, one placed either side of the wing membrane. Interestingly the thicknesses of corresponding layers in each distributed Bragg reflector are very similar for all but the second layer from each outer surface. This one key difference creates the significant disparity between the reflected spectra from the distributed Bragg reflectors and the observed colours of either side of the wing. Modelling indicates that modifications to the thickness of this layer alone create a greater change in the peak reflected wavelength than is observed for similar modifications to the thickness of any other layer. This results in an optimised and highly effective pair of semiotic reflector systems, based on extremely comparable design parameters, with relatively low material and biomechanical costs.