Mesocallis (Mesocallis) platycaryae Qiao, 2020

Chen, Jing, Jiang, Li-Yun & Qiao, Ge-Xia, 2020, Review of Mesocallis Matsumura from China (Hemiptera, Aphididae), with one new species, ZooKeys 1003, pp. 19-30 : 19

Mesocallis (Mesocallis) platycaryae Qiao sp. nov. Figures 1-12 , 13-15 , 16-24 , Table 1

Etymology.

The specific name Mesocallis platycaryae is based on the host plant ( Platycarya ) of the species.

Description.

Apterous viviparous female: body oval (Fig. 13 ), translucent white in life. For morphometric data, see Table 1 .

Mounted specimens.

Body dorsum pale; antennae, legs, cauda, anal plate, and genital plate pale, apex of rostrum brown (Fig. 13 ). Dorsal body setae thick long and dark brown, with elevated bases, sparsely spinulose shafts on part of length and large round knobs at apices (Figs 4-8 , 13 , 20-22 , 24 ).

Head. Frons convex (Figs 1 , 17 ). Dorsal setae on head similar to dorsal body setae. Head with one pair of frontal setae (Figs 4 , 16 , 17 ), one pair of setae between antennae and two pairs of posterior marginal setae between eyes (Figs 1 , 16 , 17 ). Frontal setae 5.67-6.00 × as long as basal diameter of antennal segment III. Eyes with relatively few facets (Figs 1 , 16 ). Antennae 5-segmented, 0.29-0.33 × as long as body (Figs 2 , 18 ), segments III-V with spinulose transverse imbrication; processus terminalis 0.81-0.88 × as long as the base of the segment. Antennal setae very few short and pointed; segments I-V each with 2, 2, 2 or 3, 2, 1 setae, respectively; processus terminalis with four apical setae. Length of setae on segment III 0.33-0.40 × as long as basal diameter of the segment. Primary rhinaria not ciliated (Figs 2 , 18 ). Rostrum (Figs 3 , 17 ) reaching back to between fore and mid-coxae; ultimate rostral segment thick wedge-shaped, 1.39-1.56 × as long as its basal width, 0.74-0.78 × as long as second hind tarsal segment, with two accessory setae

Thorax (Fig. 13 ). Pronotum with 1 pair of short, pale brown, anterior spinal setae and 2 pairs of thick, long, dark brown marginal setae; meso- and metanotum each with one pair of spinal and one pair of marginal thick, long, dark brown setae. Mesosternal furca separated (Fig. 5 ). Femur and trochanter partially fused; hind femur and trochanter 4.66-5.00 × as long as greatest width of segment; 1.42-1.48 × as long as antennal segment III. Distal half of tibiae and tarsi with spinulose transverse striae (Fig. 19 ); hind tibia 0.35-0.36 × as long as body. Setae on legs fine, pointed; tibial distal setae similar to other tibial setae; length of setae on hind tibiae 1.38-1.50 × as long as middle diameter of segment. First tarsal segments each with five ventral setae, and without dorsal setae. Second hind tarsal segment 1.13-1.28 × as long as processus terminalis, 0.79-0.86 × as long as antennal segment IV. Empodial setae flabellate.

Abdomen. Abdominal tergites I-VII each with a single pair of spinal and a pair of marginal setae (Figs 5-7 , 13 , 20-22 ), marginal setae on tergites I and V distinctly shorter than ones on tergites II-IV (Figs 20 , 21 ), setae on tergite VII very much shorter and pointed, not elevated at base; sometimes spinal setae on tergites III and V slightly shorter than other spinal setae; tergite VIII with one pair of thick long and dark brown dorsal setae (Figs 8 , 24 ). Marginal setae on tergite I are 5.33-9.20 × as long as basal diameter of antennal segment III; dorsal setae on tergite VIII 10.17-10.40 × as long as basal diameter of antennal segment III. Siphunculi truncated (Figs 9 , 22 , 23 ), 0.68-0.75 × as long as their basal widths, 0.38 × as long as cauda. Cauda knob-shaped, with spinulose short striae (Figs 10 , 24 ); 0.27-0.28 × as long as its basal width, with 6-8 long and short pointed setae. Anal plate bilobed, with short spinulose striae (Figs 11 , 24 ). Subgenital plate transversely oval (Fig. 12 ), with sparse spinulosity in transverse lines; with nine anterior setae, six to eight posterior setae. Gonapophyses fused, with eight short gonosetae.

Third instar nymph. Body oval (Fig. 14 ), pale brown. Cauda circular at apex, otherwise similar to apterous viviparous female.

Fourth instar nymph. Body oval (Fig. 15 ), pale brown. Cauda circular at apex, otherwise similar to apterous viviparous female.

Embryo. Dorsal body setae thick, long, and with terminal large round knobs. Head with three pairs of anterior dorsal setae, and two pairs of posterior marginal setae; pronotum with two pairs of spinal setae and one pair of marginal setae, some anterior spinal setae minute; meso- and metanotum each with one pair of spinal and one pair of marginal setae; abdominal tergites I-VII each with one pair of spinal and one pair of marginal setae; among spinal setae of metanotum and tergites I, III, and V are minute, marginal setae on tergites I-III and V-VII; spinal setae on tergites III, V, and VII are displaced.

Specimens examined.

Holotype: apterous viviparous female, China (Anhui Province: Yuexi County, Yaoluoping Reserve, Xiaoqiling, alt. 1100 m), 19 Jul. 2007, no. 20714-1-1-1, on Platycarya strobilacea , coll. J.J. Yu (NZMC). Paratypes: 1 apterous viviparous female, 1 third instar nymph, and 1 fourth instar nymph (NZMC), the collection data is the same as in the holotype.

Taxonomic notes.

Based on the following morphological characteristics in apterae and nymphs of dorsal body setae with round knobbed apex, 5-segmented antennae, much shorter than the body, hind tibial distal setae similar to other setae on the segment, distal part of tibiae and tarsi spinulose, and abdominal tergites I-VII each with one pair of marginal setae, the new species should clearly be placed in Mesocallis . The species is characterised by the dark-brown dorsal body setae, which are placed on unsclerotized tuberculate bases, and by its colonisation of Platycarya strobilacea ( Juglandaceae ). Mesocallis platycaryae resembles M. taoi in the number of antennal segments, the ratio of antennae to body length, the length and the number of accessory setae of ultimate rostral segment etc., but apterae differ from those of M. taoi as follows: dorsal body setae dark brown, not arising from sclerites ( M. taoi has the dorsal body setae pale but on pigmented sclerites); shafts of dorsal body setae largely smooth, only sparsely spinulose on part of length (vs long dorsal body setae with spinulose shafts); antennae and tarsi pale (vs distal part of antennal segments III-V and tarsi brown). The new species differs from M. carpinicola and M. pteleae in: ultimate rostral segment 0.06 mm long, and with two accessory setae ( M. carpinicola and M. pteleae : 0.10-0.14 mm long, with four or more accessory setae), head vertex and antennal segments I-III pale (vs blackish), cauda with 6-8 setae (vs 7-15 setae). In addition, the new species may be distinguished from M. obtusirostris by: antennae 0.46-0.48 × as long as body ( M. obtusirostris : antennae 0.61-0.75 × as long as body), ultimate rostral segment 0.74-0.78 × as long as second hind tarsal segment (vs 0.50-0.55 ×). The difference between the new species and other species of subgenus Mesocallis may be found in the key below.

Distribution.

China (Anhui).

Host plant.

Platycarya strobilacea ( Juglandaceae ).

Biology.

The species lives scattered on the underside of leaves of host plant.

Figures

Figures 1 - 12. Mesocallis platycaryae sp. nov. Apterous viviparous female 1 dorsal view of head 2 antennal segments I-V 3 ultimate rostral segment 4 frontal seta 5 marginal seta on abdominal tergite I 6 spinal seta on abdominal tergite III 7 marginal seta on abdominal tergite III 8 spinal seta on abdominal tergite VIII 9 siphunculus 10 cauda 11 anal plate 12 subgenital plate. Scale bars: 0.05 mm.

Figures 13 - 15. Mesocallis platycaryae sp. nov. Dorsal view of body 13 apterous viviparous female 14 4 th nymph 15 3 rd nymph. Scale bars: 0.1 mm.

Figures 16 - 24. Mesocallis platycaryae sp. nov. Apterous viviparous female 16 dorsal view of body, dorsal setae shown 17 dorsal view of head, antennal segments I-II, and ultimate rostral segment 18 antenna, fore tibia and tarsal segment 19 hind tibia and tarsal segments 20 marginal setae on antennal segments I-IV 21 marginal setae and marginal setae on abdominal tergites IV-V 22 siphunculi, spinal and marginal setae on abdominal tergites VI-VIII, cauda and anal plate 23 siphunculus 24 dorsal setae on abdominal tergite VIII, cauda, and anal plate. Scale bars: 0.05 mm.