﻿ Neothelaxespileata, a new species from China (Hemiptera, Sternorrhyncha, Aphididae, Thelaxinae)

﻿Abstract Neothelaxespileata Qiao sp. nov., found on Pileamartinii (Urticaceae) in China, is described and illustrated. Neothelaxes Chakrabarti & Quednau is also a new generic record for China.


Introduction
The aphid genus Neothelaxes was erected by Chakrabarti and Quednau (1996), with Neothelaxes viticola Chakrabarti & Quednau, 1996 as the type species. The generic diagnosis is based on the dorsal body setae arranged in single rows, not in groups, and the presence of minute wax gland pores on the sclerites. At present, there are only two known species, Neothelaxes parthenocissi Chakrabarti & Quednau, 1996 and N. viticola (Blackman and Eastop 2020;Favret 2020). Recently, some unusual specimens were collected on Pilea martinii (H. Lev) Hand-Mazz. (Urticaceae) in the Tibetan plateau, China, and they are here described as a new species, Neothelaxes pileata Qiao sp. nov. The genus Neothelaxes is newly recorded from China.

Materials and methods
The procedure used for processing and preparing the aphid specimens for microscopic study followsed that of Jiang et al. (2016). The descriptions and drawings provided here were produced from slide-mounted specimens using a Leica DM4000B with a drawing tube attached. The photomicrographic images were prepared with a Leica DM2500 using DIC illumination and processed with the Automontage and Photoshop software.
Aphid terminology in this paper generally follows that of Chakrabarti and Quednau (1996). The unit of measurement is millimetres (mm). The holotype and seven paratypes are deposited in the National Zoological Museum of China, Institute of Zoology, Chinese Academy of Sciences, Beijing, China (NZMC), and one paratype is deposited in the Natural History Museum, London, UK (NHMUK).

Taxonomy
The Thelaxinae (sensu Remaudière and Stroyan 1984) is a small group of aphids, at present comprising the genera Thelaxes Westwood, Glyphina Koch, Kurisakia Takahashi, and Neothelaxes Chakrabarti & Quednau. Species of the first three genera are associated with woody trees: Thelaxes includes oak-feeding species (Fagaceae), Glyphina species are associated with Alnus and Betula (Betulaceae), and Kurisakia species are associated with Juglandaceae and Fagaceae. On the other hand, Neothelaxes is recorded only on climbing woody rattan or herbaceous plants such as Parthenocissus (Vitaceae) (Chakrabarti & Quednau, 1996) and Pilea martinii (Urticaceae). Among the four genera, only Neothelaxes is covered with dorsal waxy plates. This genus has a restricted distribution, with the previously-described species occurring only in the Indian Northwest Himalaya and the new species restricted to the southern Tibetan plateau. Species of the genus are probably endemic to the region. Etymology. The specific name pileata is an adjective based on the feminine generic name of the host plant.

Neothelaxes pileata
Description. Apterous viviparous female: Body small, oval (Figs 12,23). Adults light dirty green, or dirty yellowish green, nymphs yellowish green, covered with white waxy powder in life (Fig. 23), and found in irregularly spherical galls on the leaves of the host plant. For morphometric data see Table 1.
Mounted specimens. Body dorsum pale brown (Fig. 12). Antennae, legs, cauda, anal plate, and genital plate brown, siphunculi and apex of rostrum dark brown. Head to abdominal segment VII fused, sometimes with intersegmental boundary on spinal area between head and pronotum and pronotum and mesonotum, and on spinopleural areas of abdominal tergites; abdominal segment VIII free (Fig. 12). Dorsal setae of body spine-like (Figs 6, 7). Wax plates large, with many minute wax pores (Figs 15,(17)(18)(19). Vertex with one pair of wax plates, pronotum to abdominal tergites I-VII each with one pair of spinal and one pair of marginal wax plates, tergite VIII with a spino-pleural wax plate (Figs 15,(17)(18)(19). Spiracles small and round, spiracular plates small and oval, brown.
Abdomen. Abdominal tergites with two or three pairs of spinal and one pair of marginal setae; tergite VII with one pair of spinal and one pair of marginal setae (Fig. 19); tergite VIII with one pair of spinal and two pairs of marginal setae (Fig. 21). Length of marginal setae on tergite I 0.50-0.63× basal diameter of antennal segment III; dorsal setae on tergite VIII 0.56-0.75× basal diameter of antennal segment III. Siphunculi almost poriform (Figs 8, 18, 20), on tergite VI surrounded by three hair-  (Fig. 23). Vertex arc-shaped, head dorsum smooth, with distinct median suture (Fig. 24). Dorsal setae on head short and pointed, head with one pair of cephalic setae, two pairs of setae between antennae, three pairs of marginal setae and one pair of anterior spinal setae between eyes; length of cephalic setae 0.83× basal diameter of segment III. Eye 3-faceted. Antennae 5-segmented (Fig. 25), segments I-IV smooth, segment V with spinulose imbrications; antennal setae slightly long and pointed, segments I-V each with 2, 2, 0, 2-3, 2+5 setae, respectively; length of setae on segment IV 1.0× basal diameter of antennal segment III; segment III 0.032 mm, respective length in proportion of segments I-V as follows: 100, 100, 100, 77, 154+77; processus terminalis 0.50× base of the segment. Primary rhinaria round and ciliated. Rostrum reaching abdominal segment IV; ultimate rostral segment elongate wedge-shaped (Fig.  26), 2.82× its basal width, 1.35× hind second tarsal segment; with one pair of accessory setae and two pairs of primary setae. Dorsal setae of thorax and abdomen spine-like, similar to adults. Thorax dorsum each with one pair of spinal and one pair of marginal wax plates, respectively. Pronotum with one pair of spinal and one pair of marginal setae, mesonotum and metanotum each with one pair of spinal, one pair of pleural and two pairs of marginal setae. Trochanter fused with femur. Distal half of tibiae and tarsi with spinulose stripes, the other half of tibiae smooth (Fig. 27). First tarsal chaetotaxy: 2, 2, 2. Abdominal tergites I-VII each with one pair of spinal and one pair of marginal wax plates (Fig. 28); tergite VIII covered with wax plate (Fig. 28). Abdominal tergites I-VII each with one pair of spinal and one pair of marginal setae (Fig. 28); tergite VIII with two dorsal setae (Fig. 28); length of marginal setae on tergite I and dorsal setae on tergite VIII 0.83× and 0.33× basal width of antennal segment III, respectively. Siphunculi invisible. Cauda circular at apex, with two setae (Fig. 28). Anal plate broadly circular, with four setae (Fig. 23). Cauda and anal plate with spinules.
Embryo ( Biology. The specimens were found within an irregularly spherical gall on the leaves. Compared to the other two species in Neothelaxes, which are not known to form galls, the biology of this new species is unusual, interesting, but less well known. Comments. According to some morphological features-3-faceted eye in apterae; fused head and thorax; 5-segmented antenna; processus terminalis shorter than base of the segment; antennal segment V, tarsi, and apices of tibiae spiculose; siphunculi poriform and surrounded by setae; cauda knob-shaped-the new species is regarded as belonging to the subfamily Thelaxinae. This new species is similar to those of Neothelaxes based on dorsum of body with waxy plates, dorsal body setae short and spine-like, and primary rhinaria ciliated. However, it differs from the type species of the genus, N. viticola, as follows: first tarsal segment chaetotaxy: 4, 4, 2 or 3 (in N. viticola first tarsal segments with 5-5-7 setae); dorsum of body pale brown, without distinct sclerites (in N. viticola vertex and spinal, marginal, and pleural sclerites of body dorsum distinct); antennae at most 1/3 of body length (in N. viticola 1/2 of body length); antennae of embryo 5-segmented (in N. viticola 4-segmented); infesting plants of Pilea (Urticaceae) (N. viticola infests the genus Parthenocissus (Vitaceae)).
Of the four known genera of Thelaxinae (sensu Remaudière and Stroyan 1984), Thelaxes, Glyphina, and Kurisakia are associated with woody trees (Fagaceae, Betulaceae, Juglandaceae), wheras Neothelaxes is known only from climbing woody rattan (Vitaceae: Parthenocissus) (Chakrabarti & Quednau, 1996). No species of Thelaxinae was previously known to live in galls. The new species is associated with an herbaceous plant and was found in leaf galls. These traits are very different from those of other species of Thelaxinae. The association with the galls is unusual and needs further confirmation from a full colony of aphids in a gall.
In view of the present findings on its host association and gall inducing nature as well as several other characters, the new species is placed in the genus Neothelexes. Further surveying and research on its biology, for example the rearing of additional adults (especially alatae) from additional galls, will be necessary to elucidate the appropriate taxonomic placement of the new species.