Xylococculus betulae (Pergande)

Hodgson, Chris & Foldi, Imre, 2006, A review of the Margarodidae sensu Morrison (Hemiptera: Coccoidea) and some related taxa based on the morphology of adult males, Zootaxa 1263 (1), pp. 1-250 : 1-250

Xylococculus betulae (Pergande)

( Fig. 15 )

Xylococcus betulae Pergande (in Hubbard & Pergande), 1898: 19.

Material studied

USA, Vermont, Moosalamoo , on beech, 22.vi.1977, W.E. Wallner ( USNM): 2/ 2♂♂ (one fair, from which most data taken, and the other poor) .

Mounted material

Large, 2.82 mm long, 0.62 mm wide across prealare. Body covered in numerous quite short hair­like setae (hs), most about 15–40 but some 70 m long; hairs (hrs) smaller, frequent; collared setae (cs) absent; almost all membranous areas with numerous setae, plus loculate pores (lp) present on both surfaces of head and prothorax but absent from venter of meso­ and metathorax and abdomen, each 4–8 m wide, with several loculi of varying size. Convex pores (cp) absent. Antennae long, flagellar segments all quite narrow, parallel­sided, becoming slightly shorter near apex; each segment with some satellite setae (sats). Sclerotised areas without nodulations. Legs well developed and setose, with many spur­like setae but apparently none bifurcated; tarsi 2 segmented; claw without a denticle; claw digitules acute. Abdominal segment I not visible ventrally; abdomen with large tubular ducts with longitudinal ridges on tergites VI and VII; without lateral caudal extensions. Penial sheath more or less terminal.

Head

Triangular in dorsal view, length 310 m, width across compound eyes 550 m. Dorsally: postoccipital suture (pos) well developed, extending across posterior part of epicranium (dmep); postocciput (poc) present posteriorly, small and triangular. Midcranial ridge (mcr) quite broad, extending full length of dorsal part of epicranium (dmep) and fusing with pos posteriorly; sclerotised. Postero­medial part of dmep quite strongly sclerotised, becoming membranous anteriorly and laterally. Preocular ridge (procr) probably represented by a short sclerotisation extending medially from between each compound eye and scape. Dorsal epicranium (dmep) covered in 32–35 hs on each side, plus some hrs and 10–14 lp. Laterally: compound eyes (cde) each about 185–200 m long, with about 110 ommatidia; with a narrow, sclerotised ocular sclerite (ocs) present along dorsal and posterior margins, each with a single dorsal ocellus (o), close to postoccipital suture (pos), each ocellus 50 m wide; each ocular sclerite (ocs) probably with a sclerotised, longitudinal postocular ridge (pocr) along dorsal margin; ventral projection (p) short but distinct and extending ventrally. Ventrally with a strongly sclerotised series of ridges forming a five­armed cross, composed of: (i) a ventral midcranial ridge (vmcr) anteriorly, which fuses posteriorly with (ii) a pair of lateral preocular ridges (procr) and (iii) a pair of preoral ridges (pror) posteriorly; preoral ridges probably articulating with a pair of small ventral sclerites (vs) laterally. Ventral part of epicranium (vmep) largely sclerotised postero­medially, becoming membranous anteriorly and laterally; setal distribution as follows: anteriorly between mid­cranial ridges and antennae with 8–10 hs, a few hrs + 6–9 lp; lateral area between preocular (procr) and preoral ridges (pror) with 8–12 hs, mainly medially, + 0 lp; area posterior to preoral ridges and around mouth (m) unsclerotised and without setae or pores. Cranial apophysis (ca) probably short and broad. Anterior (ata) and posterior tentorial arms (pta) not detected; tentorial bridge (tb) distinct, transverse, about 125 m long. Ventral sclerites (vs) present just posterior to each compound eye. Mouth (m) present medially in neck region.

Antennae: 10­segmented; length 1.8 mm (ratio of total­body length to antennal length 1:0.64); without a sclerotised articulatory socket with head, but with a strong basal articular process (bap) extending from lateral margin of each scape posteriorly. Scape (scp) 140 m long, 115 m wide, sclerotised, with 22 short setae; without bifurcated setae (bs). Pedicel (pdc) 95 m long, 75 m wide; with 10 short setae (no satellite setae (sats)), plus 5 campaniform sensilla (camp) on dorsal surface. Segments III–X of flagellum parallel­sided, each about 50–65 m wide, becoming slightly shorter near apex; each segment with 18–40 fs, each 100–113 m long, some with up to 3 satellite setae (sats). Segment X with 3 bristles (ab) near apex; no basiconic sensilla (bass) or capitate setae (caps) present. Segment lengths (m): III 275, IV 215, V 225, VI 200, VII 195, VIII 175, IX 165 and X 150.

Thorax

Prothorax: neck distinct. Dorsally with a strong pronotal ridge (prnr) which extends uninterrupted across hind part of neck but which does not reach cervical sclerite (cv) ventrally; prnr widening slightly medially on dorsum. Post­tergites (pt) complex: mainly composed of a longitudinal sclerite, about 113 m long, with a broad area of sclerotisation on either end, with anterior sclerotisation appearing similar to an apophysis, and with posterior sclerotisation slightly larger. Laterally with a pair of strong cervical sclerites (cv) which possibly articulate anteriorly with both posterior ventral sclerite (vs) and preoral ridge (pror); cervical sclerite with a small proepimeron (epm 1). Pleural ridge (plr 1) short; pleural apophysis (pla 1) distinct. Ventrally: prosternum (stn 1) with a well­sclerotised median ridge about 200 m long, which broadens anteriorly but without obvious sternal apophyses (stn 1 a) posteriorly. Most membranous areas with short setae and lp, as follows: dorsally with a group of median pronotal setae (mpns) + lp extending between posttergites over anterior end of prescutum; with a few lateral pronotal setae (lpns) just posterior to pronotal ridge (prnr); with groups of anterior and posterior propleural setae (pl 1 s) + lp on each side, clearly separated; ventrally with a distinct group of 9 or 10 anteprosternal setae (astn 1 s) + lp on each side anterior to prosternum (stn 1), and with a group of about 14 prosternal setae (stn 1 s) + lp on each side of prosternum. Antemesospiracular setae (asp 2 s) either absent or fused with posterior propleural setae (ppl 2 s).

Mesothorax: dorsally: prescutum (prsc) large and approximately oval (length 240 m, width 350 m); mesoprephragma (phr 1) narrow; prescutal ridges (pscr) short; prescutal sutures (pscs) less sclerotised than prescutum; prescutum without prescutal setae (prscs). Scutum (sct) sclerotised throughout: distance from prescutum to scutellum 240 m; with about 17 hs scutal setae (scts) + 5–8 lp on each side medially; without setae or pores near lateral margin. Scutellum (scl) roundly triangular (150 m long, 250 m wide); without membranous areas laterally; without scutellar setae (scls) or pores; posterior transverse ridge extending along posterior margin of scutum to posterior notal wing process (pnp) broad. Laterally: prealare (pra) elongate. Tegula sclerite (teg) well developed, each with 14–18 short hs tegular setae (tegs) but no lp. Mesopleural ridge (plr 2) well developed, with a deep pleural apophysis (pla 2). Mesepisternum (eps 2) not nodulated. Mesothoracic spiracles (sp 2) relatively small, outer part of peritreme 40–50 m wide and rather unsclerotised. Ventrally: basisternum (stn 2) large, length 350 m, width 495 m; with a complete, sclerotised median ridge (mdr) although poorly sclerotised in parts; bounded anteriorly by a well­developed marginal ridge (mr) and posteriorly by well­developed precoxal ridges (pcr 2); with a total of 31 short hs basisternal setae (stn 2 s) on each side, mainly medially in a line along mdr but also with a small group anteriorly; furca (f) moderately narrow ventrally, slightly waisted, with quite long arms, which diverge strongly; lateropleurite (lpl) not strongly sclerotised, without an extension from marginal ridge; subepisternal ridge (ser) unusual, broad posteriorly, with a group of about 28 hs (lpls) on posteroventral area of mesepisternum (eps 2); some setae also present along each mesoprecoxal ridge (pcr 2) and in membranous area near mesopleural apophysis (pla 2). Postmesospiracular setae (pm 2 s): with up to 24 hs in a group posterior to each spiracle (sp 2) and 4–6 medially anterior to marginal ridge (mr); no lp present. Wing sclerites: apparently showing nothing distinctive.

Metathorax: dorsally: metapostnotum (pn 3) large and extending full width of segment; with a group of 23 metatergal setae (mts) + 8 lp extending across segment. Laterally: suspensorial sclerites (ss) present. Pleural ridge (plr 3) well developed; precoxal ridge (pcr 3) well developed and extending about 180 m medio­ventrally, with a group of 5–10 hs on ventral end; with a moderately deep pleural apophysis (pla 3). Metepisternum (eps 3) slightly sclerotised with a large group of postmetaspiracular setae (eps 3 s); metepimeron (epm 3) represented by a strong sclerotisation extending dorso­posteriorly around metacoxae, and with an area of lesser sclerotisation dorsally. Posterior spiracles (sp 3) similar in structure to anterior spiracles, each about 42–55 m wide. Ventrally: metasternum (stn 3) with a large area of sclerotisation medially and large sclerotised apophyses (stn 3 a) laterally. Postmesoprecoxal ridge setae (ppcr 2 s) abundant in an elongate group along posterior margin of each precoxal ridge (pcr 2) but pores absent; with a total of about 55 anterior metasternal setae (amss) but no lp; posterior metasternal setae (pmss) (without lp) in a large group medially plus a small group laterally

Wings: quite large and well developed; each 2.65–3.0 mm long and 1.03–1.12 mm wide. Subcostal thickening (sclt) well developed; wing anterior to sclt well sclerotised proximally, becoming less so towards wing tip; rest of wing membranous but with large, broken micro­ridges; with a distinct group of 7 or 8 circular sensoria (sens) near sclt close to wing base, plus about 17 sens on distal half of wing near sclt. Alar setae (als): with 5 setae associated with each basal group of sens plus a single setae more laterally. Radius (rad) vein very faint. Alar lobe (al) represented by a sclerotised fold along proximal posterior margin. Hamulohalteres (h) mainly sclerotised, rather long and narrow; length 255–290 m, width 65–70 m; with 3 hamuli (ham), each highly curved; possibly without a clavate apex.

Legs: metathoracic legs perhaps marginally longest. Coxae (cx) lengths (m): I 275; II

250–260; III 250; each with about 60–75 longer setae along lateral margins plus a small group of shorter setae near basal articulation. Trochanter (tr) + femur (fm) lengths (m): I 500; II 520; III 540; trochanter with 33–55 shortish setae + 2 long flagellate setae, longest about 125 m, other slightly shorter; trochanter with a group 5–8 round campaniform sensilla (camp) on each side; femur with about 90 setae, most shortish but some along ventral margin long. Tibia (ti) lengths (m): I 620; II 700; III 740; distal 2/3rds with spurlike setae laterally and ventrally, these replaced by long flagellate setae dorsally; bifurcated setae (bs) absent; tibial spurs (tibs) distally without clavate apices, longest about 35 m long. Tarsi (ta) 2 segmented, proximal segment (ta 1) very short and triangular; length of ta 1 + ta 2 (m): I 180; II 200; III 210; with a tarsal campaniform sensillum (camp) (on segment ta 2); without bifurcated setae (bs), all setae short and setose; tarsal spurs (tabs) absent; tarsal digitules (tdgt) probably represented by 2 small, fine setae on dorsal margin near claw. Claws (c) broad, without a denticle (cd); claw III about 37 m long, with 2 fine setose digitules (cdgt).

Abdomen

Without caudal extensions (ce). Tergites (at) present across all segments, covering full width of segments III–VIII; sternites (as) present across all segments, covering almost full width of each segment; pleurite (apt) of segment VIII mildly sclerotised. Dorsal abdominal setae (ads) rather less frequent than ventral abdominal setae (avs), tergites I–V each with about 30–40 (total) hs ads (longest seta 50 m, shortest 25 m — all finer and more flagellate than avs) + 7–20 lp; tergites VI and VII each with 20–25 hs + 7–14 lp along anterior margin and 5–10 hs + 1–8 lp along posterior margin; segment VIII with a total of 18 hs + 2 lp. Sternites (as) each with 75–100 hs avs without lp (longest about 65 m, shortest 12 m). Additionally, on segments VI and VII, each tergite with a broad band of large tubular ducts (tdc) (each about 10 m wide), each duct conical, with a broad inner ductule 22–25 m long and 7–9 m wide, each ductule with about 8 longitudinal inner ridges, giving it a ridged appearance; with about 34–36 tdc on segment VI, and 22–24 on segment VII, both in 2 or 3 rows. Other pores absent. Tergite of segment VIII without either lp or tubular ducts (tdc). Pleural setae divided into dorsal (dps) and ventral (vps) groups; dps in groups of 9 or 10 hs + 4 or 5 lp; vps in groups of 11–14 hs + 0 lp on segments I to VI, but fusing with dps more posteriorly. Abdominal spiracles (asp) apparently absent — no tracheae could be detected in abdomen of any specimen.

Genital segment: anus (an) small, present medially above base of penial sheath. Penial sheath (ps) sclerotised, extending posteriorly from beneath segment VIII; about 245–265 m long, 185–200 m wide anteriorly, narrowing to a short, blunt apex posteriorly; with a group of 5–8 small hs penial sheath setae (pss) medially (each about 15–30 m long) on ventral surface anterior to aedeagus, plus a group of 10–12 rather longer setae (each 30–65 m long) on each side (pss); also with a small group of small sensoria (psp) on apex. Aedeagus (aed) sclerotised, almost parallel­sided, apparently without a bifid apex; 175 m long, 45–50 m wide at base; emerging from a ventral groove in penial sheath; with a short basal rod (bra) at anterior end of aedeagus, length perhaps 10 m; a very long setiferous, eversible endophallus (eph) present internally.

Comment

The most obvious differences between X. japonicus and X. betulae are: (i) tibial spurs clavate on former but not on the latter; (ii) the structure of the loculate pores, which are clearly loculate, with broad septa between each loculus on X. japonicus but have unevensized loculi on X. betulae , with fine septa between each loculus, and (iii) the length of the antennae, which are much longer on X. japonicus (about 2.7 mm as against 1.8 mm on X. betulae ).

On the basis of male structure, there seems little justification in separating Xylococculus from Xylococcus .

Figures

FIGURE 15. Male Xylococculus betulae (Pergande). Letters as for Fig. 6 except U = apical antennal segment.