Trionymus thulensis, Green

Hodgson, Chris, 2005, The adult males of Coccoidea (Hemiptera: Sternorrhyncha) known from Greenland, Zootaxa 907, pp. 1-48 : 29-34

TRIONYMUS THULENSIS Green ( Fig. 6 )

Trionymus thulensis Green, 1931: 267 ; Ben­Dov, 1994: 530; Gertsson & Hodgson, 2005: 2 (key) Pseudococcus thulensis (Green) ; Ossiannilsson, 1955: 6 (record from Iceland).

(Described from 6 specimens, 1 in quite good condition (although broken into 2 parts and lacking 1 antenna), 2 in fair condition and 3 in fair to poor condition).

Live appearance: not recorded.

Mounted material: small, total body length about 1.03–1.20 mm; antennae slightly more than half total body length, with short, stout fleshy setae (fs); length of fs on antennae about 1/2–2/3 width of antennal segments; body with few setae, all hair­like (hs), fs apparently undifferentiated from hs or absent from body; loculate pores (lp) each with mainly 3 to 5 loculi and each 5–7µm wide; many with a minute pore nearby. Wings slightly shorter than total body length, about 0.9x total body length and about 0.4x as wide as long. Abdomen with 1 pair of glandular pouches.

Head: bluntly triangular, apex of triangle pointing anteriorly; probably with ventral eyes on a distinct postero­ventral bulge; length about 144–155µm; width across genae about 170–200µm. Median crest (mc) absent; postoccipital ridge (por) represented by a thin U­shaped ridge at posterior end of dorsal midcranial ridge (dmcr); with (on each side) about 9–11 hs dorsal head setae (dhs) + 3–5 lp mesad to each scape. Mid­cranial ridge: dorsal ridge (dmcr) distinct, long and narrow, extending posteriorly well past posterior margin of dorsal simple eyes (dse) and fusing with post­occipital ridge (por); ventral midcranial ridge (vmcr) absent and without reticulations laterally; with 3 or 4 hs ventral midcranial ridge setae (vmcrs). Genae (g) not reticulated; with 2 or 3 hs genal setae (gs) on each side. Eyes: two pairs of round, simple eyes, subequal in size; dorsal eyes (dse) each approximately level with ventral simple eyes (vse); dorsal eyes, each 26–30µm wide, ventral eyes each 28–30µm wide. Ocelli (o) fairly pronounced, situated laterally, each about 23–25µm wide, lying just dorsad to where interocular ridge (ior) and postocular ridge (pocr) meet. Ocular sclerite (ocs) lightly sclerotised, with reticulations restricted to immediately around simple eyes. Preocular ridge (procr) dorsally extending medially to just past anterior inner margin of dorsal simple eyes; ventrally forming interocular ridge (ior). Postocular ridge (pocr) strongly developed, extending antero­laterally, ending posterior to inner margin of dse; each fusing with ior just ventral to each ocellus. Interocular ridge (ior) strong between base of each scape and postocular ridge. Dorsal ocular setae (docs) absent. Ventral head setae (vhs): with 6–10 hs ventral head setae (vhs) on each side anterior to each vse, distributed in a transverse band, plus 2–3 hs between eyes. Preoral ridge (pror) probably absent or poorly developed. Cranial apophysis (ca) possibly represented by a thumb­like extension.

Antennae: 10 segmented and filiform; 590–648µm long (ratio of total body length to antennal length 1:0.56). Scape (scp) approximately square, with pedicel arising more or less anterolaterally: 43–50µm long and 44–48µm wide, with 5 or 6 hs, mainly dorsally and on inner margin. Pedicel (pdc): length 63–67µm, width 34–38µm; with concentric ridges on distal end; with 8 or 9 fs (all on ventral surface) + 11–17 hs; campaniform pore present. Segments III–IX each rather variable in width, about 20–30µm wide; lengths of segments (µm): III: 83–90; IV: 58–65; V: 60–75; VI: 60–66; VII: 58–66; VIII: 56–65; IX: 53–58; fs about 11–18µm long; approximate number of setae per segment: III: 5–8 fs + 7 or 8 hs; IV: 14 fs + 2 hs; V: 17–22 + 2 or 3 hs; VI: 11–13 fs + 3 or 4 hs (on this and more distal segments, hs longer than those more proximally but without capitate apices); VII: 8–13 fs + 5 or 6 hs; VIII: 11 or 12 fs, 5 hs + 1 bristle (abr) (near distal end); IX: 9 or 10 fs, 5 hs + 1 abr (near distal end). Segment X not constricted: length 66–90µm; with 5–7 long hs, probably mainly capitate setae (caps) but without capitate apices, 10 or 11 fs + 3 large abr near apex (these clearly differentiated from fs) plus 2 shorter abr very similar to fs; with 1 or 2 sensilla basiconica (sb) near apex.

Thorax. Prothorax: pronotal ridges (prnr) well developed but not fused dorsally; long, extending ventrally and nearly touching proepisternum + cervical sclerite (pepcv); pronotal sclerite (prn) represented by a small finger­like area extending postero­laterally; without lateral pronotal setae (lpns). Medial pronotal setae (mpns): on each side 0–3 hs + 2–4 lp; post­tergite (pt) possibly present, with 0 or 1 post­tergital setae (pts). With 1–3 hs lateral prothoracic setae (lps) + 3 or 4 lp per side. Sternum (stn1) unsclerotised; median ridge absent, transverse ridge well developed; with a total of 5 hs prosternal setae (stn1s) + 7 lp. Anteprosternal setae (astn1s) and pores absent; with 2–4 hs antemesospiracular setae (asp2s) + 3 lp per side (but group fusing with prosternal setae and lp medially).

Mesothorax: prescutum (prsc) oval, 78–83µm long, 120–128µm wide; sclerotised but not reticulated; prescutal ridge (pscr) well developed anteriorly but narrowing posteriorly; prescutal suture (pscs) poorly developed or absent; with 3–6 hs prescutal setae (prscs) on each side. Scutum (sct): with a longitudinal, narrow, less sclerotised area medially; rest of scutum sclerotised but not reticulated; distance between prescutum and scutellum 70– 75µm; scutal setae (scts): 5 or 6 hs + 0 minute pores on each side; with a distinct small sclerotised apodeme (praa) on anterior margin near prealare (pra); prealar ridge (prar) quite well developed. Scutellum (scl) 83–92µm wide and 53–58µm long; without a scutellar ridge (sclr) or foramen; scutellar setae (scls): 0 or 1 hs + 0 or 1 minute pore on each side; postnotal wing process (pnp) strong and extending laterally. Basisternum (stn2) 165–195µm wide and 124–132µm long; without a median ridge (mdr); bounded anteriorly by a strong marginal ridge (mr); posteriorly with a strong precoxal ridge (pcr 2); with a narrow, short, additional sclerotised ridge, extending ventrally from pcr2 near articulation with mesocoxa; with 5–8 hs basisternal setae (stn2s) on each side, mainly in a broad median band and along anterior margin, each mainly about 25–27µm long; lateropleurite (lpl) narrow; furca (f) well developed, narrow­waisted, arms very divergent and extending about 1/2 way to marginal ridge anteriorly. Mesopostnotum (pn2) well developed; postnotal apophysis (pna) well developed. Area bounded anteriorly by scutellum and laterally and posteriorly by an unsclerotised mesopostnotum Mesepisternum (eps2) not reticulated; subepisternal ridge (ser) long and well developed. Postalare (pa) without reticulations; without postalare setae (pas). Mesothoracic spiracle (sp2): width of peritreme 21–23µm. Postmesospiracular setae (pm2s): with 5–9 hs + 1 or 2 lp posterior to each spiracle plus 2 lp medially. Tegula (teg) present, with 2–4 tegular setae (tegs) on each side.

Metathorax: with 1 hs metatergal seta (mts) on each side; metapostnotum (pn3) present as a transverse sclerite. Dorsal part of metapleural ridge (plr3) present; with small suspensorial sclerites (ss). Posterior part of metapleural ridge (plr3) well developed; episternum (eps3) sclerotised but without postmetaspiracular setae (eps3s) or pores; precoxal ridge (pcr3) well developed, extending medially about 75µm, almost to metasternal apophyses; metasternal apophysis (st3a) not located. Metepimeron (epm3) very short or absent. Antemetaspiracular setae (am3s) absent. Metathoracic spiracle (sp3): width of peritreme 22µm, without associated lp. Dorsospiracular setae (dss) absent. Metasternum (stn3) membranous, with 4 hs anterior metasternal setae (amss) + 3 lp, and 1 or 2 hs posterior metasternal setae (pmss) + 1 or 2 lp on each side.

Wings: hyaline, rather short, 1000–1075 µm long and 412–425µm wide (ratio of length to width 1:0.41; ratio of total body length to wing length 1:0.93); alar lobe (al) well developed; each wing with 2 or 3 hs alar setae (als), plus 2 or 3 circular sensoria (sens) just distal to where medial vein branches from radial vein. Hamulohalteres (h): 83–93µm long, 23–27µm wide; with a single apical hamulus (ham), 50µm long.

Legs: metathoracic legs marginally longest. Coxae (cx): I: 95–100; II: 82–95; III: 100µm long; setae of coxa III: about 9–14 hs; long setae on each coxa not differentiated. Trochanter (tr) + femur (fm): I: 219–236; II: 215–224; III: 217–232µm long; trochanter III with 5 or 6 hs; each trochanter with 3 circular sensoria on each side arranged in a triangle medially and with strong sclerotised ridges for articulation with femur; long trochanter seta 65–88µm long; femur III with about 20–23 hs, all about 25–34µm long. Tibia (ti): I: 182–191; II: 195–207; III: 227–248µm; tibia III with a total of about 31–33 setae, none fs; several others becoming spur­like on distal third of leg; with 2 or 3 spurs (tibs) on protibia, 2–4 on mesotibia and 2 or 3 on metatibia, strongest 17–23µm long. Tarsi (ta) two segmented, proximal segment very short and ring­like, length of both segments combined: I: 86–96; II: 87; III: 89–98µm long (ratio of length of tibia III to length of tarsus III 1:0.40); tarsus III with 18 or 19 setae, mainly spur­like, none fs; tarsal spurs (tabs) not differentiated, but seta in this position about 16µm long; tarsal campaniform pore (tcp) present; tarsal digitules (tdt) as long as claw, with small capitate apices. Claws (c) long and thin, nearly 1.5x width of tarsus, almost straight, without a small denticle (cd); length: III: 27– 29µm; claw digitules (cdt) probably present and setose, about 10µm long.

Abdomen: segments I–VII: tergites (at) and sternites (as) unsclerotised. Caudal extension (ce) of segment VII absent. Dorsal abdominal setae (ads) (totals across segment): segment I: 0 or 1 hs + 0 lp; II–VII: 5 or 6 hs + 0 or 1 lp. Pleural setae: dorsopleural setae (dps) on each side: I: 1 or 2 hs + 6 lp; II–VI: 1–4 hs + 5–7 lp; VII: 3–6 hs + 5 lp; ventropleural setae (vps) (on each side): II–VII: 1 or 2 hs + 0 or 1 lp. Ventral abdominal setae (avs) (totals): II: 2 hs + 0 lp; III–VII: 3–5 hs + 0 or 1 lp. With a pair of distinct ostioles (os) laterally between segments VI and VII.

Segment VIII: tergite (at) and sternite (as) sclerotised, latter without a pair of short transverse sclerotisations medio­laterally; tergite without hs dorsal abdominal setae; sternite without ventral abdominal setae (avs); caudal extension (ce) rounded, with 2 or 3 hs pleural setae. Glandular pouches (gp) present, shallow, each with numerous loculate pores spreading out around glandular pouch (gp); with 2 rather long glandular pouch setae (gls), each about 182–210µm long, plus 2 shorter setae, each about 58–75µm long.

Genital segment: penial sheath (ps) short, broadest anteriorly, sides converging to a fairly narrow, blunt apex; covered dorsally by a broad, elongate membranous area, this becoming sclerotised posteriorly, probably representing segment IX; with a vertical anal opening (an) at posterior end, about 35µm wide. Length of penial sheath 93–110µm, greatest width 93–106µm. Ventral lateral processes of penial sheath well developed, each with 1–3 short setae (each about 8µm long); ventral surface with 3 or 4 other pairs of short setae, each about 11–15µm long; with 3 pairs of longer setae (each 23–27µm long) near apex. Basal rod (bra) short but distinct, probably lying more or less vertically, perhaps about 18–23µm long to top of aedeagus (aed) (including heavily sclerotised area which probably represents internal genital aperture (iga)). Aedeagus (aed) more or less parallelsided, extending a little past end of penial sheath, about 66–83µm long and about 10µm wide, curved, lying within penial sheath.

Material examined. GREENLAND: Godhavn, 18.vii.1992, no collector: 1/2adΨΨ; as previous, 19.vii.1992 ( ZMUC): 1/1adΨ; as previous, 20.vii.1992: 2/4adΨΨ; Kangerdluarssuk tugdleq, Poa glauca , 25.vii.2003, T. Nielsen: 4/9immɗɗ; Narsarsuaq, pit­fall trap, 4.vi.2004, Jens Böcher: 5/3adΨΨ + 6adɗɗ ( ZMUC; BMNH; USNM).

Comment. Because the males were collected at the same time as some females (even though in a pit­fall trap), the identity of these males is highly probable.

Unlike the males of the other two Trionymus species described here, the males of T. thulensis do not have fleshy setae on the epicranium. In addition, T. thulensis differs from the other two species in (character­states on others in brackets): (i) generally having 4 or 5 disc­pores on each side of each abdominal segment (rarely more than 2); (ii) abundant disc­pores on prothorax, particularly ventrally (rarely 1 disc­pore ventrally); (iii) fleshy setae on antennae short and quite broad (much longer and thinner); (iv) disc­pores present ventrally on metathorax (absent); (v) only 2 hs genal setae on each side (at least 4, including some fs); (vi) disc­pores present dorsally on head (absent), and (vii) postmesospiracular setae absent medially anterior to basisternum (present).

In Afifi's (1968) key to adult males, this species comes out close to Nipaecoccus / Trionymus . It is similar to Afifi's description of the male of T. newsteadi (Green) in having no fleshy setae on the head, but the latter species is otherwise more similar to T. bocheri and T. elymus .

Figures

FIGURE 6. Adult male of Trionymus thulensis Green. Where A = cranial apophysis; E = fleshy setae; G = multilocular disc­pores; H = minute pore; J = apical antennal segment; K = lateral view of genital segment; L = tarsus plus claw.