Morphology, taxonomy, and systematic position of the enigmatic aphid genus Sinolachnus (Hemiptera: Aphididae, Lachninae)

Abstract Here, we present a revision of the poorly studied aphid genus, Sinolachnus from the tribe Tuberolachnini of the subfamily Lachninae (Hemiptera: Aphididae) modified to include eight species. Apterous and alate viviparous females of the type species S. niitakayamensis are redescribed together with alate viviparous females of Sinolachnus elaeagnensis. Alate viviparous females of a new species Sinolachnus takahashii sp. nov. and apterous and alate viviparous females of Sinolachnus yushanensis sp. nov. associated with Elaeagnus oldhamii, from Taiwan are described. Sinolachnus is, for the first time, recorded from Japan and the alate viviparous female of Sinolachnus nipponicus sp. nov. is described. Additionally, we recognize two other species of the Lachninae as members of this genus: Sinolachnus plurisensoriatus (Zhang, 1988) comb. nov. (= Cinara plurisensoriata Zhang, 1988) from China, and Sinolachnus rubi (Ghosh & Raychaudhuri, 1972) comb. nov. (= Maculolachnus rubi Ghosh & Raychaudhuri, 1972) from India. We have designated the lectotype for Sinolachnus niitakayamensis. For the first time, we have provided scanning electron microscopy analyses to show the morphology and sensilla of this genus. Following comparative analyses with other Tuberolachnini and Lachninae genera, we propose to transfer the genus Sinolachnus from the tribe Tuberolachnini to the Tramini. http://urn:lsid:zoobank.org:pub:ED1A226C-6DEA-4F17-9669-1D2E33E86566


Introduction
Owing to their complicated morphology, polymorphism and life cycles, aphids are fascinating insects. They play an important role in ecosystems and as plant pests and viruses vectors, making them one of the most economically significant groups. Members of the subfamily Lachninae are one of the most interesting groups, not only within Aphididae but among insects generally. Members of the Lachninae can feed on both green and woody parts of both conifers and broadleaved plants (Chen et al. 2016). From the beginning of the 21 st century, Lachninae aphids have received attention from many researchers in terms of their phylogeny and evolution (Normark 2000;Jousselin et al. 2013;Chen et al. 2016;Théry et al. 2018) as well as their morphology, biodiversity, systematics and taxonomy (Kanturski & Wieczorek 2014;Kanturski et al. 2016Kanturski et al. , 2017aKanturski et al. , 2017b. The Asiatic representatives of Lachninae have received the least attention in recent years in studies involving scanning electron microscopy and molecular research (Chen et al. 2017;Kanturski et al. 2017cKanturski et al. , 2018aKanturski et al. , 2017dKanturski et al. , 2017e, 2018bChakrabarti et al. 2020). One of the most important and interesting Lachninae groups are the poorly known members of the tribe Tuberolachnini, which, besides the almost cosmopolitan Tuberolachnus salignus Gmelin, are characterized to be Asiatic Lachninaes. Recognition of the Tubelolachnini as a tribe has been validated by molecular studies (Normark 2000;Chen et al. 2016) and it comprises four genera: Tuberolachnus Mordvilko, Nippolachnus Matsumura, Pyrolachnus Basu & Hille Ris Lambers and Sinolachnus Hille Ris Lambers of which Sinolachnus is the least known. Representatives of Sinolachnus are known from their association with Elaeagnus species (maybe also with other Elaeagnaceae) where they feed on branches and are constantly visited by ants. Sinolachnus spp. most probably prefer higher mountain areas of South-East Asia. The first species of the genus Sinolachnus was described from Taiwan by Takahashi (1925) as Lachnus niitakayamensis; Takahashi noted that the only known alate viviparous female was characterized by antennae with numerous sensilla on each segment, previously known only in the males of aphids (Takahashi 1925). Two years later, Takahashi (1927) described the apterous viviparous females and in the next years (Takahashi 1931) transferred L. niitakayamensis to the genus Lachniella Del Guercio. Hille Ris Lambers (1956) erected Sinolachnus, a new genus for L. niitakayamensis mostly due to the "sensoriation of the antennae of alatae, which is unique in aphids". Additionally, Hille Ris Lambers highlighted the "first tarsal joints with several short sensillae and some longer hairs". The genus remained monotypic until the description of the second species, known from a single alate viviparous female captured in a Malaise trap: S. taiwanus (Tao, 1989). The least known species of this genus, S. elaeagnensis, has been described by Chakrabarti and Das (2015) from Bhutan (Remaudière & Remaudière 1997;Favret 2022). Sinolachnus still remains the most poorly known genus not only in Tuberolachnini but also within Lachninae as a whole. Representatives of this genus so far never have been investigated in terms of morphology or relationships with other genera beyond the rather arbitrary decision of Chen et al. (2016) to put Sinolachnus within Tuberolachnini genera. In the course of several years of research by the first author on Asiatic Lachninae, all known available material of Sinolachnus has been gathered together with the material of species described in other genera (e.g. Cinara Curtis and Maculolachnus Gaumont). We hereby present the results of the revision of the poorly known genus Sinolachnus to include eight species. We report Sinolachnus from Japan for the first time with a description of a new species, and describe a new species from Taiwan. We propose to transfer two species already described in other Lachninae genera: Cinara plurisensoriata Zhang, 1988 and Maculolachnus rubi Ghosh & Raychaudhuri, 1972 to Sinolachnus. We provide detailed scanning electron microscopy analyses of apterous and alate viviparous females as well as of alatoid nymphs to show the morphology and sensilla of Sinolachnus for the first time. Moreover, after comparison with other Lachninae genera, we propose to transfer Sinolachnus to the tribe Tramini.
This paper is a part of the project "Morphology, diversity and phylogeny of Asiatic Tuberolachnini aphids".

Study material and light microscopy
The slide-mounted material, obtained from different collections, was fixed in Canada balsam. Freshly collected samples were preserved in 70% ethanol for several days. Alcohol-fixed samples were transferred to 10% KOH and boiled. After maceration and removing the embryos, the samples were transferred to chloral phenol for one hour and finally to the Chloral hydrate. Samples were then transferred to a Faure-Berlese solution and dried in an incubator for about one week in 40°C.
All existing and available slides of representative Sinolachnus have been examined for this study. The specimens were examined using a light microscope Leica DM 3000 LED and photographed by Leica MC 190 HD camera. The measurements were done according to Ilharco and van Harten (1987); Blackman and Eastop (2006). Measurements are given in millimeters. Material examined of each species is given in the review of species. Actual host plant names are given according to The Plant List (2013). Final figure processing was done using Photoscape 3.7 (photoscape.org) and Irfanview 64 (irfanview.com).
The following abbreviations are used: ANT antennae or their lengths

Scanning electron microscopy
Specimens for SEM analyses were preserved in 70% ethanol for several days. From ethanol, the specimens were transferred into 6% phosphotungstic acid (PTA) solution in 70% ethanol for 24 hours. Dehydration was accomplished through an ethanol series of 80%, 90%, 96% and two changes of absolute ethanol for 10 minutes each. Absolute ethanol dehydrated specimens were treated with chloroform for 24 h. Dehydrated and cleaned samples were dried using the Leica EM CPD 300 auto-critical point dryer (Leica Microsystems, Vienna, Austria). Dry samples were mounted on aluminum stubs with double-sided adhesive carbon tape and sputtercoated with 30 nm gold layer in a Quorum 150 T ES Plus sputter coater (Quorum Technologies Ltd, Laughton, East Sussex, UK). The specimens were imaged by the Hitachi SU8010 field emission scanning electron microscope FESEM (Hitachi High-Technologies Corporation, Tokyo, Japan) at 7 and 10 kV accelerating voltage with a secondary electron detector (ESD). Final figure processing was done using Photoscape 3.7 (photoscape.org) and Irfanview 64 (irfanview.com).

Notes on
Sinolachnus SEM morphology based on S. yushanensis 3.1.1. General morphological characters. Apterous viviparous females of S. yushanensis are pear-shaped and very densely covered by numerous long, fine and pointed setae (trichoid sensilla). The head is separated from thorax of which each segment (pronotum, mesonotum and metanotum) is also separated from each other and from ABD I. Abdominal segments I, ABD VII and VIII are well separated from one another (Figure 1(a)). Siphunculi are quite low and situated on very protuberant and hairy sclerites. Additionally, the surface of SIPH sclerite is wrinkled or ruffled (Figure 2(a)). The perianal structures of the end of the abdomen are well adapted to ant attendance with short or even hidden cauda, the almost vertical anal plate with characteristically protruded hairs forming a "basket-like" structure ( Figure 2(b)-(e)). Between anal and genital plates, three rudimentary gonapophyes are visible (Figure 2(f)). The cuticular surface varies by bodily region. All body parts and appendages are densely covered by trichoid sensilla (setae), which are characterized by very protuberant sockets. Trichoid sensilla on the body are long, sometimes hairlike, with very fine and pointed apices (Figure 3(a) and (b)). The cuticle on the head and pronotum cuticle is smooth with moderate corrugation (Figure 3(c)). The surface of mesonotum is visibly covered by numerous minute scales or denticles that are similar to triangles with pointed apices (Figure 3(d) and (e)). The metanotum and the remaining abdominal tergites (especially ABD I-VI) are characterized by cuticle with very clear polygonal sculpturing in the form of pentagons or hexagons ( Figure  3(f)-(h)). The edges between each polygon are rather irregular and often, additional inner rigidity is visible within each polygon (Figure 3(i)). The polygonation is not only restricted to the dorsal part of the body, but also lateral sides in the area of spiracles are polygonal and richly sculptured (Figure 3(j)). As mentioned previously, the trichoid sensilla are long and fine, their surface is longitudinally ribbed and the sockets are quite narrow and protuberant (Figure 3(k) and (l)). Alate viviparous females are characterized by rather well developed and sclerotized thorax. Both alate viviparous females, as well as alatoid nymphs, are densely covered by numerous setae (trichoid sensilla) and their cuticular surface characters are the same as in apterous viviparous females ( Figure 4). In alate viviparous females, the eyes are larger with more ommatidia ( Figure 5) and three ocelli are visible (Figure 5(b) and (c)). Triommatidia are distinct and placed on protuberant tubercle ( Figure 5(d)). Similarly as in the apterous viviparous female, SIPH sclerite surface in alate females is wrinkled or ruffled and the apex of the SIPH terminates in a rather flat flange and semicircular operculum ( Figure 5(f)). The perianal structures are very hairy and similar to those of apterous females ( Figure 5(g)). The dorsal abdomen of the alate female of S. yushanensis is covered by some amount of wax in the form of granular and oblong secretions (Figure 5(h) and (i)). Those secretions were visible despite of chloroform treating. Alate viviparous females are characterized by numerous surfaces covered by polygonal (most probably strengthening) sculpture which is visible even on the distal half of the antennal pedicel ( Figure 6(a) and (b)). Most of the body surface is also covered by a thin but visible wax layer that moreover has not been removed during the treatment with a chloroform bath. This layer can be noted on the head (Figure 6(c)) and mostly on the abdomen ( Figure 6(d)-(f)). In some places when the secretions have been removed, the cuticle presents a serrated sculpture (Figure 6(g)-(i)). Alatoid nymphs present a similar head morphology to the alate female (Figure 7(a)). Only the eyes are characterized by smaller number of ommatidia which are absent from the dorso-proximal part (Figure 7(c)). Moreover, the cuticle of the dorso-proximal part of the eyes bears a few small but well-visible openings that may be openings to sensory structures (Figure 7 (d)-(f)). Cuticle of the alatoid nymph is rather similar as in the apterous and alate viviparous females with some distinct exceptions in the area and directly on the wing buds. The wing buds are in general smooth or slightly wrinkled, covered by numerous trichoid sensilla (Figure 8(a), (b) and (f)-(h)). The cuticle of the proximal part of especially fore wings buds are characteristically porous or even spongy (Figure 8(c)-(e)). The thoracic cuticle is strongly wrinkled with wide denticles forming rather transverse lines rather than polygonal cells (Figure 8(i) and (j)) which are clearly visible on the abdomen (Figure 8(k) and (l)). SIPH sclerites are of the same characters as in apterous and alate females but lying on smaller and lower sclerites (Figure 8(m)), and the perianal structures (especially the shape of cauda and anal plate) are almost the same as in the apterous female (Figure 8(n) and (o)).

Antennal sensilla.
In apterous viviparous females, the antennae bear several types of sensilla of which type I trichoid sensilla are the most numerous and in the form of long, very fine, hair-like setae with almost filamentous, pointed apices (Figures 9 (a) and (b); 10(a)). Type I trichoid sensilla are distributed on all antennomeres except the terminal process and have protuberant and trapezoid sockets (Figure 10(a) and (b)). On its basal portion, the surface of the sensilla is smooth, graduating to a visibly ribbed surface (Figure 10(b)). On ANT VI terminal process apex, a second type of trichoid sensilla can be found: type II. Those forming the apical and subapical setae, are short, stiff with rounded sockets and ribbed on the whole length ( Figure 10(c)-(e)). In contrast to type I trichoid sensilla the type II sensilla are characterized by blunt or slightly rounded apices with a granulose surface ( Figure 10(f)). During the examination of the apterous viviparous antennal flagellum besides type I trichoid sensilla, small multiporous placoid sensilla, big multiporous placoid sensilla and sunken coeloconic sensilla have been found (Figure 9(c)-(e)). In the apterae of S. yushanensis, small multiporous placoid sensilla have been found on ANT IV and V as secondary rhinaria and on ANT VI BASE as primary (accessory) rhinaria. Small placoid multiporous sensilla on ANT IV and V are rather small, rounded, slightly protuberant and lie in depressions of the cuticle (Figure 11(a) and (b)). Antennomere V bears also big placoid sensillum on the distal end (Figures 9(d);11(b)). The sensillum is visibly protuberant without any sclerotized collar or projections. The sensillum surface is covered by numerous minute pores (Figure 10(c) and (d)). Most types of sensilla on ANT VI are distributed on the BASE and consist of big multiporous placoid sensillum (major rhinarium) with almost all accessory rhinaria lying on the lateral side of the major rhinarium and one small placoid sensillum moved far from the other ones to the terminal process (Figure 9(e)). The structure and porous surface of the big placoid sensillum (major rhinarium) are the same as on ANT V. The rest of the accessory rhinaria are forming by two small multiporous placoid sensilla in polar positions, between which four sunken coeloconic sensilla are distributed ( Figure 11(e)). Accessory rhinaria lying at the major rhinarium are located separately deep in cuticle depressions and are surrounded by cuticular collars ( Figure 11(f)). In contrast to small multiporous placoid sensilla on ANT IV and V those ones on ANT VI present quite different and unique morphological structures as spheres or club-shaped projections, and the one sensillum on the terminal process is the more visibly protuberant and exposed on a rounded basal part ( Figure 11(g) and (h)). Sunken coeloconic sensilla can be divided into two types: type I with short projections and type II with long projections (Figure 11(i)). In alate viviparous females, we were able to examine sensilla of the pedicel and three types of sensilla have been found. On the ventral side of the pedicel one highly visible rhinariolum has been found in the form of exposed coeloconic sensillum type I with short projections and a very low sclerotic collar (Figure 12 The sensilla (secondary rhinaria) are very characteristically protuberant and distributed slightly irregularly or in irregular lines on the whole surface of antennomeres ( Figure 13(b) and (c)). They are also of different sizes and some of them may fused into larger ones which are very similar to the large placoid multiporous sensilla ( Figure 13(d)-(f)). Each of the small multiporous placoid sensilla extends far from the antennomere cuticle and is composed of the robust sclerotic collar, an extension of the cuticle and semispherical multiporous membrane with densely distributed pores (Figure 13(g)-(i)). The large placoid sensillum on ANT V, bearing numerous pores on the membrane, is characterized by larger openings of the sensillum membrane which are rather regularly distributed on the sensillum plate ( Figure  13(j)-(l)). The type I trichoid sensilla on alate viviparous females are characterized by a more ribbed structure (Figure 14(a)) but overall they are similar as in apterous morphs. Beyond all the types of sensilla mentioned in apterous females, the antennal segment VI of alate viviparous females bears small placoid sensilla which are the secondary rhinaria on the proximal part of the BASE (Figure 14(b)). The arrangement of the sensilla forming primary rhinaria is similar to that of the apterous morphs with the large multiporous placoid sensillum (major rhinarium) and 3.1.3. Mouthparts sensilla. The labium (rostrum) both in the apterous and alate viviparous females is long. The first segment is short, membranous and without sensilla. The second segment is the longest, sclerotized and covered by trichoid sensilla. Third segment is short and bulbous. The ultimate rostral segments (IV and V) are tapered and pointed ( Figure 16(a)). In apterous viviparous females, ultimate rostral segments (URS) from the ventral, lateral and dorsal sides are in the form of more or less regular triangles and are densely covered by long, fine trichoid sensilla (Figure 15(a)-(c)). The sensilla are characterized by rounded sockets and their surface is smooth (Figure 15(d) and (e)). On the proximal part of RIV, occur a pair of type II basiconic sensilla (sometimes hidden) which are much shorter than trichoid sensilla, with the apices more blunt (Figure 15(f) and (g)). The last fifth segment is quite well separated from the fourth one and bears seven pairs of long, stiff and rounded apices type III basiconic sensilla on the very tip ( Figure 15(h)-(l)).
In alate viviparous female mouthparts, the ultimate rostral segments in particular share similar features as in apterous viviparous females (with some exceptions). In alate viviparous females, the trichoid sensilla sockets appear more protuberant and trapezoid ( Figure 16(b), (c) and (m)), strongly ribbed and the extreme tip is slightly blunt (Figure 16(d) and (e)). Also the cuticle of the segments seems to be more sclerotized and covered by longitudinal reinforcement (Figure 16(f)). Type II basiconic sensilla are slightly longer, stiff with evident sockets, visibly ribbed and with very slightly blunt apices ( Figure 16(g)-(l)). There are eight pairs of type III basiconic sensilla which are, similar to those of apterous viviparous females, long and clearly visible even under low magnification (Figure 16(n) and (r)), stiff ( Figure 16(o), (s) and (t)) and with more or less rounded apices (Figure 16(q) and (u)). On the basal part of the sensilla, a well-developed molting pore can also be found (Figure 16(p)).

Wing morphology and sensilla.
Fore wings in alate viviparous females are characterized by morphology rather typical for most Lachninae. The pterostigma is clearly visible and covered by numerous scale-like elements. The wing venation is well marked, with protuberant radial sector, media and concave cubital veins (Figure 17(a)) which are concave (radial sector and media) and protuberant (cubital veins) on the dorsal side of the wing membrane ( Figure 17(b) and (c)). The ventral side of the wing is also characterized by the claval fold near Cu1b (Figure 17(a)). On the basal part of the wing, numerous campaniform sensilla can be found (Figure 17(d) and (e)). The campaniform sensilla are protuberant, with a rounded outer collar and two forms of internal structure: rounded ( Figure 17(f)) and indented in the outer collar ( Figure 17(g)). In both types of sensilla, pores in the central part of the inner part are visible. Rounded campaniform sensilla are arranged along the concave Sc+R + M+ Cu veins (Figure 17(h)). The wing membrane is covered by numerous crescent-shaped scale elements and a very thin wax layer ( Figure 17(i), (j) and (n)). The scale-like elements become more semicircular or almost circular near the edges of the wings (Figure 17(k)). The convex veins are (especially near the wing edges) formed by single ruffled structures, which appear to be the wing membrane protuberances  (b)). On the basal part of the hind wings, a large group of campaniform sensilla can be found, but they are always fewer in number than those on fore wing ( Figure 18(c)). As on the fore wing, they are protuberant, rounded and the pore in the center of the inner portion is Interestingly, on the lateral side of the basal part of hind femora of alate viviparous females (in the region with campaniform sensilla), a very small and rounded opening in the cuticula has been found which is similar to those of the sensilla ampullaceal ( Figure 20(e), (f) and (h)). The legs are densely covered by numerous long, fine, hire-like in the distal part and with pointed apices trichoid sensilla (Figures 19(c) and (e); 20(i)-(k)). As on the antennae and mouthparts, their sockets are protuberant, oval or rounded from the top and trapezoid from the lateral side and their surface is smooth in the basal part but later becomes prominently ribbed (Figure 19(d) and (e)). Tarsi are characterized by the first segment with short dorsal length (Figures 19(g); 20 (l)), normal-shaped claws and greatly reduced parempodia (empodial setae) (Figures 19(i); 20(n)-(p)) strictly in form of very short pegs (a bit longer in alate viviparous females). First segments of tarsi are characterized by two kinds of ventral setae: long, more fine and pointed; and short, peg-like ones which are stiffer and with less pointed apices (Figures 19(h); 20(m)). Also, the sockets of the sensilla are of different sizes -larger in the long setae and smaller in the peg-like setae. The ratio of the number of short, peg-like setae to the long ones is the largest on the first segment of prothoracic tarsi (Figures 19(j); 20(q)), later on the first segment the mesothoracic tarsi (Figures 19(k); 20(r)) and the lowest on the first segment of metathoracic tarsi (Figures 19 (l); 20(s)). ANT III with type I trichoid sensilla, (c) ANT IV with type I trichoid sensilla and one small multiporous placoid sensillum (Orange) -secondary rhinarium, (d) ANT V with type I trichoid sensilla, one small multiporous placoid sensillum (Orange) -secondary rhinarium and big multiporous placoid sensillum (yellow) primary rhinarium, (e) ANT VI with type I trichoid sensilla, type II trichoid sensilla (violet), big multiporous placoid sensillum (yellow) -major rhinarium, small multiporous placoid sensilla (green) and sunken coeloconic sensilla (pink) -accessory rhinaria.

Diagnosis of the genus Sinolachnus.
Sinolachnus aphids may be distinguished from all other Tuberolachnini and Lachninae representatives by the alate viviparous females with uniformly light brown or hyaline wings and all segments of antennal flagellum bearing extremely large numbers of very small and protuberant secondary rhinaria (e.g. 66-290 on ANT III and 14-95 on ANT IV), while in other Lachninae species alate viviparous females are characterized by larger, flatter and much less numerous secondary rhinaria (not more than 50 in Tramini). Secondary rhinaria with the exception of some Tramini are absent on the BASE of ANT VI. Apterous viviparous females can be separated from all other Lachninae species by sclerotization of the thorax and abdomen, with small denticles and a large number of "sense pegs" on first segments of especially fore tarsi (6-12), middle tarsi (2-5) and hind tarsi (2-3), while in all other Lachninae species the sclerotized part of the thorax and abdomen is smooth or at most wrinkled and the first segments of tarsi bear not more than 3 "sense pegs" (often only one). Apterous and alate viviparous females of Sinolachnus differ from other Lachninae species and genera by the characters of ANT VI accessory rhinaria arrangement. One of the accessory rhinaria lies singly at the border between BASE and PT or on the basal part of PT while the remaining accessory rhinaria are in a single group together near the major rhinarium.
= Cinara plurisensoriata Zhang, 1988 5. S. rubi (Ghosh & Raychaudhuri, 1972) Figure 11. SEM of antennal placoid and coeloconic sensilla of apterous viviparous female of S. yushanensis: (a), ultrastructure of small multiporous placoid sensillum on ANT IV, (b) small and big multiporous placoid sensilla on ANT V, (c) ultrastructure of small multiporous placoid sensillum on ANT V, (d) ultrastructure membrane of small multiporous placoid sensillum on ANT V, (e) sensilla types on ANT VI BASE: type I trichoid sensilla (blue), big multiporous placoid sensillum (yellow) -major rhinarium, small multiporous placiod sensillum (green), two kinds of sunken coeloconic sensilla (pink) -accessory rhinaria, (f) group of two types of sunken coeloconic sensilla, (g) ultrastructure of small multiporous placoid sensillum on the BASE, (h) ultrastructure of small multiporous placoid sensillum on the PT, (i) type I sunken coeloconic sensillum (with short projections) and type II sunken coeloconic sensillum (with long projections).    (Takahashi) Figure 13. SEM of antennal flagellum sensilla of alate viviparous female of S. yushanensis: (a) fragment of ANT III with numerous small multiporous placoid sensilla (secondary rhinaria), (b, c) structure of secondary rhinaria and type I trichoid sensilla on ANT III, (d) different sizes of small multiporous placoid sensilla on ANT III with one of a size of big multiporous placoid sensillum (star), (e) small multiporous placoid sensilla n ANT IV od different sizes (star), (f) small multiporous placoid sensilla (secondary rhinaria) and big multiporous placoid sensilla (primary rhinarium) on ANT VI, (g, h) ultrastructure of small multiporous placoid sensillum with well visible sclerotic collar. Arrowhead showing the border between the cuticle and porous membrane, (i) ultrastructure of the porous membrane of small sensilla, (j) big multiporous sensillum with openings on the membrane (arrows), (k) structure of the sensillum membrane with the openings, (l) ultrastructure of porous membrane and the additional opening.

ANT VI BASE
-Body larger than 2.75 mm (mostly more than 3.00 mm

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M. Kanturski et al. the rest of body densely covered by numerous long, fine and pointed setae. Head cuticle sclerotized and smooth. Antennae 6-segmented. ANT I squareshaped, ANT II with flat base and bulbous distal part. ANT III longest, as long as or shorter than ANT IV+ANT V+ ANT VI. ANT segments with small to very small rounded and protuberant secondary rhinaria on ANT III-Ant VI, often in the distal part. Primary rhinaria with sclerotic rosette. Accessory rhinaria on ANT VI often divided into two groups, with one moved to the PT and the remaining ones near the major rhinarium. PT only with five apical in two groups (2 + 3) and two subapical setae. Rostrum reaching beyond hind coxae. URS triangular. Thorax sclerotized, covered by numerous minute denticles, arranged more or less linearly. Legs normal. First segments of tarsi with different number of "sense-pegs", with the most numerous on FT I. Abdomen membranous, often with more or less developed sclerotization in the form of sclerosis and sclerites. SIPH on sclerites with mostly irregular edges and well-developed flange. ABD VII and VIII with spino-pleural sclerotized cross-bars. Abdominal cuticle wrinkled with polygonal sculpture. Cauda semi-circular. GP densely covered by setae.

Alate viviparous females.
Head with large compound eyes and visible, well-developed triommatidia. Epicranial suture clearly visible. Head and the remainder of body densely covered by long, fine and pointed setae. ANT 6-segmented with

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M. Kanturski et al. long, fine and pointed setae. Primary rhinaria with sclerotic rosette. Accessory rhinaria on ANT VI divided into two groups with one located on the PT and the rest together on the lateral side of the major rhinarium. PT with five spical setae in two groups (2 + 3) and 1-3 subapical setae. Rostrum long, reaching over hind coxae. URS narrow, triangular. Thorax sclerotized.
Fore wings hyaline or uniformly brown pigmented. Pterostigma brown of normal width and rounded apex. RS slightly curved. Both Cu veins raised separately directly from Sc+R + M+ Cu. Media poorly visible, one or twice-branched. Scale elements covering whole surface or only distal part of the wing membrane. Legs normal, densely covered by long, fine and pointed setae. HT I with different number of "sense-pegs" with the most numerous on FT I. Abdomen membranous with sclerotization in form of sclerites, scleroites and sclerotic plates. SIPH on sclerites with mostly irregular edges and well-developed flange. ABD VII and ABD VIII with spino-pleural cross-bars. Cauda semi-circular. GP densely covered by setae.  (3), VCK), other data as in holotype.

Diagnosis.
Sinolachnus elaeagnensis with its twice branched media is similar to S. plurisensoriatus and S. taiwanus (and differs from all other Both species differ from each other also by the differences in ANT VI/ANT III, ANT IV/ANT III and URS/ANT VI ratios. Host plant. This species has been found on an unidentified Elaeagnus species on which according to Chakrabarti and Das (2015) the aphids infest young stems. Remarks. Superficially, this species is very similar to S. plurisensoriatus, which is known from Tibet, but detailed analyses have shown undoubted distinctiveness of both species. Apterous viviparous females as well as the sexual generation remain still unknown.

Apterous viviparous female -redescription (based on Takahashi 1927)
Colour in life: Yellowish brown, blackish on the dorsal side of abdomen. Antennae yellowish brown, with black apices (Takahashi 1927). Pigmentation of mounted specimens: unknown. Morphometric characters. BL about 2.5 mm long, ANT about 1.2 mm long 0.48 × BL. ANT III shorter that the remaining segments with 0-2 rhinaria, ANT IV slightly longer than ANT V with one rhinarium near the distal end, ANT V shorter than ANT VI with one rhinarium in the middle. ANT VI PT 0.56 × BASE. Other antennal ratios: ANT VI/ANT III 0.44, ANT V/ ANT III 0.32, ANT IV/ANT III 0.33, ANT IV/ANT V 1.03. Fore femur about 1.3 mm long, longer than ANT III. Hind tarsus slightly longer than ANT VI.

Alate viviparous female -redescription
Colour in life: head antennae and thorax black. Legs black with paler proximal parts of femora. Abdomen greenish (Takahashi 1925). Pigmentation of mounted specimens: ANT brown with slightly paler basal part of ANT III, legs head and pronotum brown, legs brown with paler proximal parts of femora, abdomen yellow with light brown sclerotization (Figure 23

Host plant. Representatives of this species feed on
Elaeagnus oldchamii (Takahashi, 1926) Distribution. The species is known from Kanko in Taiwan ( Figure 40).

Remarks.
During the description of the species, Takahashi (1925) described only alate viviparous female of this species ("two winged females") and later (Takahashi 1927   Etymology. The name of the new species is derived from the name of Japan in Japanese -"Nippon" and the suffix "ensis" for species names related to places.

Host plant. Most probably any species of
Elaeagnus. This species has been collected in a cave by Japanese Collembola researcher R. Yoshii. Remarks. This is the first record of the genus Sinolachnus in Japan. This single alate has been collected during work by R. Yoshi (well known as a cave biologist) and most probably sent to R. Takahashi, who designated it as S. niitakayamensis (Lachnus on the slide). So far no other morphs, including the sexual generation, are known. (Zhang, 1988) comb. nov. Cinara plurisensoriata Zhang, 1988: 169 (Figs. 23, 27;    Distribution. Tibet, China (Figure 40).

Remarks.
Sinolachnus plurisensoriatus for several years remained unrecognized and described in the genus Cinara mostly due to the character of the pointed structure of URS (especially RV). This was most probably due to the very poor level of the knowledge of Sinolachnus as a whole. Apterous viviparous females, as well as the sexual generation, are so far unknown.

Apterous viviparous female -redescription
Colour in life: dark brown (Ghosh & Raychaudhuri 1972). Pigmentation of mounted specimens: Head and thorax brown, ANT brown with paler basal part of ANT III. Legs brown with paler proximal parts of femora. SIPH, abdominal sclerotization and genital plate brown (Figure 2(a)). Morphometric characters. HW 0.42-0.45 × ANT. Head setae 0.08-0.10 mm long. ANT 0.52-0.54 × BL. ANT III shorter than the remaining segments with 3-6 secondary rhinaria, ANT IV shorter or slightly longer than ANT V with 5-6 secondary rhinaria (Figure 28(a)), ANT V shorter than ANT VI with 3-4 secondary rhinaria (Figure 28(b)). ANT VI with 2-3 secondary rhinaria (Figure 28(c)) and PT 0.56-0.62 × BASE. Other   Host plant. This species is associated with undetermined Rubus species from which it has been collected at the altitude of 1598 m and is always attended by ants.
Distribution. So far this species is known only from Shillong in Meghalaya (India) from the type series ( Figure 40).

Remarks.
The geographic proximity to Bhutan may raise some questions if apterous viviparous females of this species and alate viviparous females of S. elaeagnensis are conspecific but we know of no study (morphological of the same morphs or molecular) to determine this and so we treat these species as separate. This species was firstly described in the genus Maculolachnus Gaumont most probably due to some superficial similarity with M. submacula apterae. The character of dorsal cuticle, presence of secondary rhinaria on ANT VI and the arrangement of accessory rhinaria in respect to the major rhinarium and finally the number of sense-pegs of particular first segments of tarsi undoubtedly indicate that the species should be treated as Sinolachnus member. There is no information on the alate viviparous females, or the sexual generation, of this species. Tao, 1989Tao 1989: 27 ( Fig. 33(g))

Alate viviparous female -redescription (based on Tao 1989).
Pigmentation: Head, antennae, two last rostrum segments, thorax, legs, stigma and veins (except media) pale. Siphunculi, ABD VII and VIII, cauda and anal plate blackish brown; the remaining anatomy white (Tao 1989) -most probably this description refers to living or alcohol-preserved samples rather than to mounted specimen. Available morphometric characters. ANT 0.68 × BL. ANT III shorter than the remaining segments, ANT IV slightly longer than ANT V, ANT V shorter than ANT VI.

Diagnosis.
We considered carefully whether to include this species in the key for alate viviparous females of this poorly known genus, for obtaining reliable results. In accordance with the description and robust comparative analyses of the remaining species with the available material, we now compare this species together with S. elaeagnensis and S. plurisensoriatus regarding the twice branched media of fore wing. Sinolachnus taiwanus differs by its much smaller body size (~ 2 mm), its hyaline wings with scale elements sparsely distributed and visible only in the distal margins, as well as in the ratio of ANT IV/ ANT V ~ 0.90. In both S. elaeagnensis and S. plurisensoriatus the alates are larger, wings are pigmented with scale elements of the whole surface of the wing, and the ratio of ANT IV/ ANT V is 0.96-.1.13.

Remarks.
Sinolachnus taiwanus is the most poorly known and enigmatic species in this genus. We were not able to examine any material as this species has been described from only one sample (not exceptional in Sinolachnus) which moreover must be recognized as lost, according to Chi-Feng Lee (Taiwan Agricultural Research Institute, TARIIC); hence, material of this species is absent in the collection. Other morphs including oviparous female and male are unknown.  Etymology. We are pleased to name the new species to honour Riochi Takahashi, an outstanding Japanese aphidologist who has worked for several years on the aphid fauna of Taiwan and was the collector of the specimens.
Host plant. Alate viviparous females of this species have been collected from an undetermined Elaeagnus species and E. oldhamii.

Apterous viviparous female -description
Colour in life: Body (head, thorax and abdomen) generally black, sometimes dark brown (different shades of brown in older larvae instars and nymphs), first instar larvae yellowish-orange. Head sometimes slightly paler than the rest of the body. From pronotum to ABD IV a narrow whitish stripe runs in the spinal area. Antennae yellow with darker ANT V and VI. Legs yellow or light brown with darker distal part of tibiae and tarsi. Freshly molted specimens are shiny, turning to a dull colour (Figure 8). Pigmentation of mounted specimens: Head and thorax brown. ANT brown with yellow pedicel and proximal half of ANT III. Legs brown with darker distal parts of femora, tibiae and tarsi. Abdomen pale brown with brown sclerotization (Figure 22(b)). Morphometric characters. HW 0.50-0.51 × ANT. Head setae 0.09-0.13 mm long. ANT 0.44-0.55 × BL. ANT III shorter that the remaining segments with 1-3 rhinaria (Figure 30(a)), ANT IV shorter than ANT V with 2-6 rhinaria ( Figure 30

Alate viviparous female -description
Colour in life: Head and antennae black. A light brown stripe lies between the head and prothorax. Thorax black. Wings uniformly dusky. Legs dark brown to black with orange proximal parts or halves of femora. Abdomen brownish-black. Freshly molted specimens with light brown head and thorax and yellow legs and wings, shiny, turning dull in older specimens ( Figure 32). Pigmentation of mounted specimens: Head and thorax brown, ANT uniformly dark brown. Wings uniformly brown pigmented. Legs brown with slightly paler proximal parts of femora. Abdomen pale brown with brown sclerotization (Figure 23  information of sensilla even on ANT V or VI (if the number of ANT was too high) and besides the relative lengths of antennal segments, he did not provide measurements for the URS and HT II which could be extremely useful. Even the diagnosis from the type species is rather poor and there are only two differences given by Tao: the body length and the information on the twice-branched media. Ultimately, the relative length of antennal segments allows us to obtain the ratios of particular antennomeres. Further, we have determined that the information on wing venation and a small number of scale-like elements ("sparsely imbricated") and ratios of antennal segments should be enough to maintain the species status of S. taiwanus as nothing more can be done without examination of the types material or other material similar to that in the description. It is puzzling that Tao described a second Sinolachnus species from the material collected in 1985 in 1989 (manuscript accepted in June, 1989) but did not discuss S. taiwanus in the "Aphid fauna of Taiwan Province" (Tao 1991), and on pages 95-96 only S. niitakayamensis is given as the representative of this genus from Taiwan. Sinolachnus taiwanus has been added to the list of species in "List of Aphidoidea (Homoptera) of China" (Tao 1999). Studies on this genus have shown and confirmed the importance of correct indication of relevant and valid features in morphological analyses in species recognition. Our results reinforced previous ones that detailed analyses have to be done as in other Lachninae genera like the European Lachnus species which, although well placed within the genus, may be confusing in species recognition despite the validity of morphological traits (Mróz et al. 2015).

Sinolachnus and other Tuberolachnini genera
Sinolachnus was previously a member of the tribe Lachnini when only three tribes of Lachninae (Lachnini, Cinarini and Tramini) were recognized (Remaudière & Remaudière 1997 and all papers until 2016). Chen et al. (2016) confirmed Normark's (2000) first results and proposed five tribes within Lachninae, with Tuberolachnini and Stomaphidini as independent taxa. As a result of their molecular research, the authors left in Lachnini the genera Lachnus, Maculolachnus, Longistigma and Pterochloroides and proposed four genera: Nippolachnus, Pyrolachnus, Sinolachnus and Tuberolachnus as members of the tribe Tuberolachnini. In fact, Sinolachnus was absent in their analyses and transferring this genus to Tuberolachnini was, potentially, arbitrary as the authors did not provide any comparison nor comment about the similarities or differences between the Tuberolachnini genera. On the other hand, it should be emphasized that Tuberolachnini is a group of genera characterized by some divergent features. The representatives of Nippolachnus are medium in size to large with very characteristic alate viviparous females (Figures 34(b); 35(b)). Moreover, Nippolachnus species feed only on the leaves and never on stems or branches like the other Tuberolachnini and most Lachninae genera (Kanturski et al. 2018b). Pyrolachnus and Tuberolachnus species (Figures 34(c) and (d); 35(c) and (d)) constitute some of the largest Lachninae (and aphids as a whole right after Stomaphis and Longistigma). Additionally, apterous viviparous females in Tuberolachnus are characterized by a dorsal abdominal tubercle and alate viviparous females of Pyrolachnus are easy to recognize due to the dusky basal part of fore wings (Figure 35(c)). On this background, Sinolachnus species (Figure 34(a)) are the smallest Tuberolachnini (additionally with the shortest tibiae) and well distinguished by their often uniformly brown pigmented wings of alate viviparous females (Figure 35(a)). The wings of Sinolachnus differ from other Tuberolachnini by shorter and wider pterostigma with gentle edges, evidently curved Cu1a and media which arises directly from the Sc+R + M+ Cu (Figures 33; 35 (a)). The wings of alate viviparous females in Nippolachnus, Pyrolachnus and Tuberolachnus wings are characterized by a long and narrow pterostigma with pointed tip, straight or only slightly (in Tuberolachnus) curved Cu1a and media which does not reach the Sc+R + M+ Cu (Figure 35(b)-(d)).
Antennae in Sinolachnus alate viviparous females are robust and their hundreds of sensilla are the best distinguishing feature (Figure 36(a)). The presence of numerous secondary rhinaria on ANT V and VI in alate viviparous females is a distinctive feature in aphids and often varies among species within a given genus. In Sinolachnus, all known alate viviparous females bear secondary rhinaria on ANT V and especially VI, whereas in Nippolachnus only some individuals (and only on one antennal segment) of N. piri bear secondary rhinaria. Beyond this feature, the antennae are characteristized by the very large rhinaria on the remaining segments (Figure 36(b)). In alate viviparous female of Pyrolachnus pyri the rhinaria are numerous but the number never reaches even the half of the number of sensilla in Sinolachnus (Figure 36(a) and (c)) and they never appear on ANT VI. Large, flat (as in Nippolachnus and Pyrolachnus) secondary rhinaria can be found also in Tuberolachnus from which they are always absent 56 M. Kanturski et al. on ANT V and ANT VI (Figure 36(d)). In the case of the arrangement of sensilla on ANT VI (position of accessory rhinaria relative to the major rhinarium), Sinolachnus species are quite distinguished from other Tuberolachnini especially by the accessory rhinaria occurring as almost singular structures, of which one (small placoid sensillum) is situated on the PT (Figures 36, 14(b); 36(e)). In the remaining genera, the accessory rhinaria always form one group of tightly adjoined structures near the major rhinarium (even in Nippolachnus in which they are almost all moved to the PT) (Figure 36(f)-(h)).
Sinolachnus differ from all other Tuberolachnini also in terms of the first segment of tarsi and the number of peg-like setae. In Sinolachnus first segment of tarsi is characterized by its extremely short dorsal length and rounded distal portion of the ventral aspect (Figure 37(a)-(c)). Also, the number of peg-like setae is the largest, especially on the fore and middle tarsi. The remaining Tuberolachnini are characterized by first segments of tarsi with long dorsal length and pointed distal part of ventral length (Figure 37(d)-(l)). Moreover, Nippolachnus species are characterized always by only one (Figure 37(d)-(f)) and Tuberolachnus by 2 or 3 peg-like setae on the first segments of tarsi ( Figure  37(j)-(l)). Only Pyrolachnus is characterized by a larger (4 or 5) number of peg-like setae on the first segment of fore tarsi and 2 or 3 on middle and hind tarsi (Figure 37(g)-(i)).

Sinolachnus and Tramini genera
Our attention has been focused not only on Tuberolachnini genera but also especially on one genus from the tribe Tramini -Eotrama and the species E. moerickei. Eotrama has been described by Hille Ris Lambers (1969) as "a link between two aphid groups" -"the relatives of Lachnus" and "the relatives of Lachnini". Hille Ris Lambers also pointed out that Eotrama is very closely related to Sinolachnus, and after extensive examination of the morphology of representatives of this genus, this is also our position. Sinolachnus apterous viviparous females are more similar to those of E. moerickei especially by the shorter tibiae and a similar ratio of antennae and body lengths (Figure 38(a) and (c)). The alate viviparous females share similarly short and wide pterostigma of blunt edges and robust antennae (Figure 38(b)-(d)). Antennal sensilla in Sinolachnus are numerous and very protuberant (Figure 39(a)) which is very similar to characters of antennal sensilla of Protrama radicis (Figure 39 (b)) and E. moerickei (Figure 39(c)). Further, Sinolachnus, Protrama and Eotrama share the presence of secondary rhinaria on ANT V and ANT VI (Figure 39(d)-(f)). This is how a major difference between Sinolachnus and Tuberolachnini in the case of Tramini becomes a similarity -the position and arrangement of accessory rhinaria relative to the major rhinarium. In Protrama (also in Trama) the secondary rhinaria, as in Sinolachnus, are in linear position and occur as singlular structures partly on the ANT VI BASE and spanning the PT (this character of ANT VI antennal sensilla is also present in Stomaphis) (Figure 39(d) and (e)). In this case, E. moerickei is the most outstanding case with secondary rhinaria rather as one group and also rather on the BASE (Figure 39(f)). What is very noticeable is the very similar morphology of the first segments of especially fore and middle (Protrama and Trama) and all tarsi (Eotrama) with first segments of tarsi in Sinolachnus representatives. As in Sinolachnus (Figure 39(g)), Tramini members are characterized by short dorsal length and rounded distal part of the ventral side and numerous evident peg-like setae on middle and fore tarsi (Figure 39(h)-(l)). Apterous viviparous females of Sinolachnus are obligatory myrmecophilous as Tramini and they are well adapted to this relationship: they can live in soil shelters made by the ants and they have the same morphological adaptations in the form of the trophobiotic organ (Figure 2(b)-(e)) recently discovered in Tramini and almost the same as in Protrama (Kanturski et al. 2017b;Kaszyca-Taszakowska & Yamamoto 2020). The old division of Lachninae (e.g. Remaudière & Remaudière 1997) was based mostly on the basis of ecological features of particular groups: Cinarini (representatives feed on conifers), Lachnini (representatives feed on stems, branches and trunks of deciduous shrubs and trees) and Tramini (representatives feed underground on the roots). Owing to the unique biology of Tramini, their monophyly has never been in doubt, and has been established firmly in the minds of aphidologists. This historical precedent may hinder our understanding of this tribe as occupying habitats above ground. According to Chen et al. (2016), at least five transitions from thick bark to other feeding sites took place during the evolution of Lachninae on angiosperms (including once in Tramini). The closeness of Sinolachnus and Eotrama has been confirmed by Chen et al. (2016), following Hille Ris Lambers (1969), but the authors decided to put it in Tuberolachnini due to the lack of root feeding and its distribution which is similar to Pyrolachnus, Nippolachnus and Tuberolachnus, although the latter have a cosmopolitan distribution.
As a result of the presented similarities and differences, we are of the opinion that Sinolachnus should be a member of this tribe as members of this genus share more similarities with Eotrama and other Tramini than with Tuberolachnini genera. The strong biological argument has been given by Chen et al. (2016) in the case of Tramini after the results of their research were found no longer relevant in the case of Stomaphidini (which feed on trunks and earlier were treated as Lachnini members which feed on deciduous trees), which lost its relevance in the case of Tuberolachnini in which Nippolachnus species feed only on leaves, whereas Pyrolachnus and Tuberolachnus members feed on the woody parts. Treating Sinolachnus as a link between Tramini allows us to advance a novel hypothesis. Maybe in the distant evolutionary past, an ancestor of this group was heteroecious and host alternating with forms which were feeding on trees and with generations on roots (common in Anoeciinae and Eriosomatinae) or other plants (Hormaphidinae, Macrosiphini). This already has been shown in Lachninae on the example of Stomaphis japonica . Certain factors may have caused the separation of the ancient taxa of which two biological distinct lineages started diverging along separate paths. The above questions may be solved even partially by future molecular studies including Sinolachnus and other Lachninae.