Metopeurum caucasicum Barjadze & Stepanyan, 2024

Barjadze, Shalva, Stepanyan, Ilona, Kalashian, Mark, Karagyan, Gayane, Gabrielyan, Ivan & Thieme, Thomas, 2024, A new species of Metopeurum Mordvilko, 1914 (Hemiptera: Aphididae) from the Transcaucasus, with a key to the species of this genus, Zootaxa 5463 (3), pp. 417-428 : 419-427

Metopeurum caucasicum Barjadze & Stepanyan sp. nov.

( Figs 1–9 , 11 , Table 1 )

Metopeurum buryatica ( Pashtshenko, 1999) : Barjadze et al. (2010: 5), misidentification.

Metopeurum buryatica ( Pashtshenko, 1999) : Stepanyan et al. (2023: 511) , misidentification.

Type material. Holotype. Apterous viviparous female, ARMENIA, Gegharkunik province, Sevan municipality, surroundings of Semenovka village , Dzknaget river gorge, 40°37’48.01"N, 44°56’14.57"E, 1945 m. alt., 25.vii.2023, Tanacetum canescens DC. , leg. I. Stepanyan, 135E23 (apt. 19 with arrow on slide), IZISU.

Paratypes. (n=44) Six apterous viviparous females on one slide, ARMENIA, Kotayk province, Megradzor municipality, surroundings of Megradzor village, 40°36'14.1"N, 44°38'07.0"E, 1777 m alt., 25.vii.2022, Tanacetum abrotanifolium Druce , leg. G. Karagyan, 089E22 (apt. 1–6), IZAY; two apterous viviparous females on one slide, ARMENIA, Kotayk province, Artavaz municipality, surroundings of Artavaz village ( Fig. 1 ), 40°38'09.0"N, 44°33'21.7"E, 1961 m alt., 08.vii.2021, Tanacetum vulgare L., leg. I. Stepanyan, 026E21 2 (apt. 7–8), IZISU; eight apterous viviparous females on one slide, other data the same as in the previous slide, 026E21 1 (apt. 9–16), IZAY; two apterous viviparous females on one slide, ARMENIA, Kotayk province, Hankavan municipality, surroundings of Hankavan village, 40°37'31.7"N, 44°28'14.0"E, 2006 m alt., 25.vii.2022, Tanacetum balsamitoides Sch. Bip. , leg. G. Karagyan, 083E22 (apt. 17–18), BMNH; five apterous viviparous females on one slide with holotype, other data the same as in holotype, 135E23 (apt. 20–24), IZISU; eight apterous viviparous females on one slide, ARMENIA, Gegharkunik province, Sevan municipality, surroundings of Semenovka village, Dzknaget river gorge, 40°39’11.6”N 44°53’17.2”E, 2014 m. alt., 25.vii.2023, Tanacetum balsamita L., leg. I. Stepanyan, 142E23 (apt. 25–32), IZAY; two apterous viviparous females on one slide, GEORGIA, Mtskheta-Mtianeti region, Stepantsminda municipality, Near Gveleti waterfall, 42°42’17.8”N, 44°36’51.6”E, 1557 m alt., 27.vii.2007, Tanacetum vulgare L., leg. Sh. Barjadze, TA–T–143 (apt. 33, 34), IZISU; eleven apterous viviparous females on one slide, ARMENIA, Gegharkunik province, Sevan municipality, Dzknaget river gorge, 40°37'48.4"N, 44°56'14.3"E, 1946 m alt., 24.vii.2023, Achillea millefolium L., leg. Ilona Stepanyan, 133E23 (apt. 35–45), IZISU.

Description. Apterous viviparous female (n=45) Color in life: a dark brown head and thorax, reddish, orange or greenish colored abdomen, black ANT, SIPH and cauda. Pigmentation on slide: ANT I–VI, head, clypeus, apical part of rostral segment II, rostral segment III, URS, coxae, femora except pale basal small portion, tibiae, tarsi, SIPH, subgenital and anal plates brown; frons brown, darker than head dorsum behind the insertion of the ANT; cauda mainly brown, rarely pale brown; stigmatic sclerites pale brown; antesiphuncular sclerites pale brown ( Figs 2–9 ).

Body oval. Frons slightly concave ( Figs 4, 6 ). ANT tubercles very low and divergent. ANT 6–segmented ( Fig. 2 ). ANT III–VI cuticle imbricated. ANT III with 8–23, rounded, different-sized sec. rhin. with well-developed sclerotised rims, occupying 0.80–0.95 of ANT III length ( Figs 2, 3 ), ANT IV with 0–6 and ANT V with 0–4 sec. rhin. Antennal chaetotaxy: ANT I with 7–10, ANT II with 4–6, ANT III with 16–24, ANT IV with 8–15, ANT V with 6–10, ANT VI with 3–4 basal, 4 apical and 6–11 setae along the PT. Rostrum reaching to, or slightly beyond to hind coxae. URS elongated, wedge–shaped with 6–8 accessory setae, which are long and pointed ( Fig. 8 ). Setae on body dorsum, antennae, and on legs fine with pointed apices except for ventral setae on tibiae, which are stout and slightly blunt ( Fig. 5 ). Femora with spinulose imbrications. First tarsal chaetotaxy: 3:3:3. Antesiphuncular sclerites developed in most specimens. SIPH long, subcylindrical, with imbrications and without distinct flange ( Figs 6, 7 ). Dorsal setae on ABD TERG VIII arise from scleroites. ABD TERG VIII with 5–12 setae. Subgenital plate oval, sclerotic, with spinulose imbrications and with 11–21 setae on the discal part and 9–16 setae on the hind margin, which are grouped as two separated clusters. Cauda mostly finger shaped or rarely triangular, rounded at apex, bearing 13–30 long and curved or almost straight setae and numerous strong dark spinules ( Figs 6, 9 ). Metric and meristic features are presented in Table 1 .

Intraspecific variation. Alive specimens on Achillea millefolium , Tanacetum balsamita and T. balsamitoides have greenish abdomen, while specimens on Tanacetum abrotanifolium , T. canescens and T. vulgare have orange or reddish colored abdomen. Ranges of measurements, ratios and chaetotaxy for Achillea - and Tanacetum -feeding Metopeurum caucasicum sp. nov. are given in Table 1 .

Diagnosis. Metopeurum caucasicum sp. nov. belongs to the Metopeurum species group which have long and acute dorsal setae, that are similar to ventral setae on abdomen in front of SIPH. Other aphid species that share this character are M. achilleae Bozhko, 1963 , M. borystenicum Bozhko, 1963 , M. buryaticum , and M. capillatum ( Mamontova & Tshumak 1994; Blackman & Eastop 2024).

Differences between the apterous viviparous females of Metopeurum caucasicum sp. nov. and M. achilleae and M. borystenicum are given in the identification key.

The apterous viviparous females of Metopeurum caucasicum sp. nov. are distinguished from those of M. buryaticum by SIPH L/BL ratio: 0.19–0.27 in the new species, while 0.16–0.19 in M. buryaticum . Other differences between the above-mentioned two species are given in the identification key.

The apterous viviparous females of Metopeurum caucasicum sp. nov. are distinguished from those of M. capillatum by pigmentation of HFEM: only small basal portion is pale, while basal half is pale in M. capillatum (Thomas Thieme’s investigation of holotype). Other differences between the above-mentioned two species are given in the identification key.

The apterous viviparous females of Metopeurum caucasicum sp. nov. are distinguished from those of M. enslini ( Börner, 1933) , M. fuscoviride , M. gentianae Mamontova & Tshumak, 1994 , M. matricariae Bozhko, 1963 , M. millefolii Mamontova & Tshumak, 1994 and M. urticae Mamontova & Tshumak, 1994 by length of dorsal abdominal setae: they are long and acute, like ventral setae anterior to SIPH, in the new species, while they are short and blunt, shorter than ventral setae anterior to SIPH, in all above mentioned Metopeurum species ( Blackman & Eastop 2024).

The apterous viviparous females of Metopeurum caucasicum sp. nov. are distinguished from those of Apiaceaefeeding M. paeke Umarov, 1964 by the number of sec. rhin. on ANT III: 8–23 in the new species, but 25–31 in M. paeke ( Narzikulov & Umarov 1969) . Other difference between the above-mentioned two species is given in the identification key.

Etymology. The specific name originates from the name of the geographic region where it was sampled.

Biology. This new species feeds on leaves, stems and inflorescences of Achillea millefolium and five species of Tanacetum : T. abrotanifolium , T. balsamita , T. balsamitoides , T. canescens and T. vulgare ( Asteraceae ). This is an ant-attended species. In Armenia, colonies of this species on Achillea millefolium , Tanacetum abrotanifolium , T. balsamita , T. balsamitoides , and T. vulgare are attended by the ant Proformica pilosiscapa . Besides, the ant Formica cinerea is associated with aphid colonies living on T. balsamita and T. balsamitoides . Alate viviparous females, sexual morphs and life cycle are unknown.

Biotope characteristics. The new Metopeurum species is distributed on host plants growing in mountain meadow steppe or meadows, between 1000–2000 m alt. in Armenia and Georgia .

In Armenia, the main vegetation types in the vicinities of Meghradzor—Artavaz villages (along the road, Marmarik river gorge) and Dzknaget River gorge are riparian forest and mountain meadow steppe. In general, the main woody species in these biotopes are Salix elbursensis , S. excelsa and S. triandra . The main herbaceous species in these biotopes are Achillea biebersteinii , A. millefolium , Artemisia absinthium , Bromus danthoniae , Cichorium intybus , Cirsium sp. , Epilobium hirsutum , Lepidum latifolium , Menta longifolia , Plantago major , Tanacetum balsamita , T. vulgaris and Taraxacum officinale .

Another vegetation type is observed in the vicinities of the Hankavan village: the meadow, broad-leaved deciduous and artificial pine forests. The main woody species are Betula pubescens var. litwinowii , Lonicera caucasica , Pinus sylvestris , Rosa spp. , Rubus idaeus , Salix caprea , Sorbus aucuparia , Viburnum lantana . The main herbaceous species are Achillea millefolium , Epilobium angustifolium , Filipendula hexapetala , Hesperis matronalis , Lactuca serriola , Lamium album , Origanum vulgare , Rumex crispus , Tanacetum vulgare .

Distribution. It is known from 7 localities in Armenia and Georgia ( Fig. 11 ).

Identification key for Metopeurum species apterous females

This key is a modification of those by Mamontova & Tshumak (1994) including Metopeurum buryaticum , M. paeke and M. caucasicum sp. nov.

1. First tarsal chaetotaxy: 2:2:2. On unknown Apiaceae . In Kirgizia.................... Metopeurum paeke Umarov 1964

-. First tarsal chaetotaxy: 3:3:3. On other plant families........................................................ 2

2. SIPH only ca. 0.5 × cauda. On Tanacetum vulgare . In Germany and Ukraine......... Metopeurum enslini ( Börner, 1933)

-. SIPH more than 1 × cauda.............................................................................. 3

3. Setae on the abdominal dorsum anterior to SIPH are short and blunt, shorter than ventral setae on abdomen............. 4

-. Setae on the abdominal dorsum anterior to SIPH are long and acute only, like ventral setae.......................... 8

4. Cauda with constriction and with less than 10 setae. The longest setae on ANT III shorter than ANT III BD. On Achillea millefolium . In Kazakhstan and Ukraine....................... Metopeurum millefolii Mamontova & Tshumak 1994

-. Cauda without constriction and with more than 10 setae. The longest setae on ANT III longer than ANT III BD.......... 5

5. Reticulated area on SIPH occupying max. 0.2 length of SIPH. On Chamomilla recutita , Tanacetum tanacetoides , Tripleurospermum inodorum (= Matricaria perforata ). In Kazakhstan, Moldova, Ukraine and Pakistan..................................................................................... Metopeurum matricariae Bozhko, 1963

-. Reticulated area on SIPH occupying more than 0.2 length of SIPH.............................................. 6

6. URS L ca. 2 × URS W. On Achillea spp. , Artemisia alba , Cladanthus arabicus , Leucanthemum vulgare , Tanacetum spp. In Europe, west Siberia, Iran and Central Asia................................ Metopeurum fuscoviride Stroyan, 1950

-. URS L less than 2 × URS W............................................................................ 7

7. Cauda with 10–15 setae. On Gentiana asclepiadea . In Ukraine.... Metopeurum gentianae Mamontova & Tshumak 1994

-. Cauda with more than 15 setae. On Urtica dioica . In Ukraine........ Metopeurum urticae Mamontova & Tshumak 1994

8. Cauda pale.......................................................................................... 9

-. Cauda pigmented.................................................................................... 11

9. ANT III with 16–33 secondary rhinaria. Cauda with 9–13 setae. On Tanacetum vulgare . In Russian federation, Kazakhstan............................................................... Metopeurum buryaticum ( Pashtshenko, 1999)

-. ANT III with 5–11 secondary rhinaria. Cauda with 8–10 setae................................................ 10

10. Reticulation occupying no more than 30% of SIPH. On Achillea millefolium , A. nobilis subsp. nobilis (= Achillea gerbera ). In Ukraine.............................................................. Metopeurum achilleae Bozhko, 1963

-. Reticulation occupying at least 40% of SIPH. On Tanacetum vulgare (= T. boreale ). In Moldova, Ukraine and Kazakhstan.................................................................... Metopeurum borystenicum Bozhko, 1963

11. ANT III with 28–32 secondary rhinaria. URS L 1.16–1.17 × HT II L. On Achillea atrata or Achillea erba-rotta moschata . In Austria............................................................. Metopeurum capillatum ( Börner, 1950)

-. ANT III with 8–23 secondary rhinaria. URS L 0.66–0.89 × HT II L. On Achillea millefolium and five species of Tanacetum : T. abrotanifolium , T. balsamita , T. balsamitoides , T. canescens and T. vulgare ( Asteraceae ). In Armenia and Georgia ................................................................................. Metopeurum caucasicum sp. nov.

Figures

FIGURE 1. Sampling site of paratypes (026E21) of Metopeurum caucasicum sp. nov. ARMENIA, Kotayk province, Artavaz municipality, surroundings of Artavaz village. Photo by Gayane Karagyan.

FIGURES 2–9. Metopeurum caucasicum sp. nov. Apterous viviparous female. 2. ANT (bar: 500 μm); 3. ANT III (bar: 200 μm); 4. Head (bar: 200 μm); 5. HTIB and HT I–II (bar: 500 μm); 6. Habitus (bar: 500 μm); 7. SIPH (bar: 200 μm); 8. Rostral III segment and URS (bar: 100 μm); 9. Cauda (bar: 200 μm). Note: All figures, except for Fig. 9, were taken from the holotype. Fig. 9 was taken from paratype 135E23 apt. 23.

FIGURE 11. Map with sampling sites of Metopeurum caucasicum sp. nov. 1. Armenia, Hankavan (083E22); 2. Armenia, Artavaz (026E21); 3. Georgia, near Gveleti waterfall (TA–T–143); 4. Armenia, Megradzor (089E22); 5. Semenovka (142E23); 6. Semenovka (135E23); 7. Semenovka (133E23).