Trionymus elymus, Gertsson & Hodgson

Gertsson, Carl-Axel & Hodgson, Chris, 2005, Four new species of mealybug (Pseudococcidae) and a new species of soft scale (Coccidae: Coccoidea: Hemiptera) from Greenland and redescriptions of a mealybug and a soft scale from Arctic Canada, Zootaxa 897, pp. 1-24 : 11-14

TRIONYMUS ELYMUS Gertsson & Hodgson spec. nov. ( Fig. 4 )

(Described mainly from 4 specimens in fair to good condition).

Unmounted material. Not known.

Mounted material. Elongate oval in outline, 1625–2550 µm long and 675–950 µm wide; anal lobes moderately developed and lightly sclerotised; antennae 8 segmented; legs normally developed; circulus present; with 2 pairs of distinct cerarii; oral rim ducts absent.

Dorsum. Membranous, with frequent fine setae, each mainly 8–40 µm long but with some on head up to 70 µm. Trilocular pores frequent and fairly evenly distributed. Simple (discoidal) pores scarce throughout; also with 2 small convex pores dorsad to each scape. Cerarii clearly present on abdominal segments VII and VIII, each with 2 stout spinose setae (stoutest on VIII), length of cerarian setae on VIII 11–18 µm, those on VII 8–11 µm; with 10–13 auxiliary setae, longest about 75 µm. Ostioles membranous, each lip of posterior pair with about 10–12 trilocular pores and no setae; anterior pair with possibly none on anterior lip and about 12 on posterior lip + 1 or 2 setae. Oral rim ducts absent. Oral collar ducts of two sizes; larger ducts (each about 2.5–3 µm wide, 5 µm long, without a thin inner ductule) frequent throughout, but most abundant on segment VII; smaller ducts (each about 1.5 µm wide, 3–4 µm long, with a long thin inner ductule) in transverse lines across abdominal segments III –VII, with about 10–20 per segment. Multilocular disc­pores 6– 7 µm wide, present as follows: VIII 0–2; VII 6–8; VI 1–7; V 1–4 and IV 0, located almost anywhere on segment. Anal ring 58–67 µm wide, with 6 setae, each about 85–100 µm long.

Venter. Membranous, with frequent fine setae, similar in length to those on dorsum, each 11–35 µm long, but some on head up to 70 µm and those around vulva about 50 µm long; suranal setae 48–60 µm long; long anal lobe setae each 135–145 µm long; anal lobe with a small sclerotised bar arising from most anterior seta. Trilocular pores frequent and fairly evenly distributed. Simple (discoidal) pores as on dorsum. Oral rim ducts absent. Oral collar ducts of two sizes as on dorsum, larger ducts present throughout but most frequent on posterior abdominal segments, particularly laterally, otherwise mainly along posterior margin of posterior abdominal segments and apparently randomly elsewhere; smaller ducts in a transverse line medially across abdominal segments III –VII and randomly on anal lobe; very scarce on thorax and head. Multilocular disc­pores 6–7 µm wide, abundant on abdomen as follows (approximate totals across segment): VIII 58 –78, throughout segment; VII 91 –114 throughout segment; VI 78 –90 mainly along posterior margin but also elsewhere; V 24–37 almost entirely along posterior margin; IV 6 or 7 along posterior margin; III 0; absent more anteriorly apart from 1–3 between each procoxa and anterior spiracle. Circulus oval to rather squarish, 60–65 µm wide and 40–43 µm long, with a distinct intersegmental fold. Eyespot about 20 µm wide. Antennae 8 segmented, 290–303 µm long; scape with 4 setae; pedicel with 4 setae + campaniform pore; segments III –VII each usually with 4 or 5 setae; preapical segment also with a fleshy seta; apical segment longest, with 10 hair­like setae, 3 fleshy setae and 4 or 5 stiff setae near apex; apical seta about 30–35 µm long. Clypeolabral shield about 125–130 µm long; labrum about 90 µm long, with 10 or 11 pairs of setae. Spiracles: width of peritremes, anterior 24– 27 µm; posterior 30–37 µm. Metathoracic legs: lengths (µm): coxa 115–125; trochanter + femur 205–225; tibia 165–183; tarsus 75–90; claw 23–25; number of setae: coxa 7 or 8 + 2 at base; trochanter 7 or 8 (longest 83–85 µm); femur 12 or 13; tibia 15–18 (plus two spurs, each 20–22 µm long); tarsus 9 or 10; translucent pores quite abundant on lateral 1 / 3 of each metacoxa (also along anterior margin on posterior surface); absent on femur and tibia. Tarsal digitules: one thinner and slightly shorter than other but both capitate; claw digitules both slightly longer than claw and capitate; claw without a denticle. Vulva obvious, between segments VII and VIII.

Material examined. HOLOTYPE Ψ: GREENLAND: Evighedsfjord, Kangiussaq, 20.vii. 2003, on Elymus mollis , S.T. Nielsen ( ZMUC): 1 / 1 adΨ + 1 adɗ.

PARATYPE ΨΨ: GREENLAND: Evighedsfjord, Kangiussaq, 20.vii. 2003, on Elymus mollis , S.T. Nielsen ( ZMUC): 2 / 2 adΨΨ + 2 adɗɗ; Itivleq, 22.vii. 2003, E. mollis, S.T. Nielsen ( BMHN): 1 / 2 adΨΨ.

Comment. The adult female of T. elymus spec. nov. is very similar to that of T. tomlini Green , but differs (character­states on T. tomlini in brackets) mainly in (i) the complete absence of multilocular disc­pores on the dorsum anterior to abdominal segment V (present on all abdominal segments) and (ii) their almost complete absence ventrally anterior to abdominal segment IV (frequent throughout venter). In addition, the degree of sclerotisation of the anal lobe appears to be less, and the smaller oral collar ducts are also absent anterior to abdominal segment III (present on all abdominal and thoracic segments).

T. elymus differs most obviously from the other Trionymus species known from Greenland ( T. bocheri described as new below and T. thulensis Green ) in having a large oval to almost square circulus, with an intersegmental membrane, whereas those on T. bocheri (described as new above) and T. thulensis are small and round and lack any intersegmental membrane.

Etymology: this species is named after the grass genus on which it was collected, Elymus .

Figures

FIGURE 4. Adult female of Trionymus elymus Gertsson & Hodgson. Labels etc as on Fig. 1.