Rhizoecus falcifer Künckel d'Herculais, 1962

Hodgson, Chris, 2012, Comparison of the morphology of the adult males of the rhizoecine, phenacoccine and pseudococcine mealybugs (Hemiptera: Sternorrhyncha: Coccoidea), with the recognition of the family Rhizoecidae Williams 3291, Zootaxa 3291 (1), pp. 1-79 : 26-29

Rhizoecus falcifer Künckel d'Herculais

( Fig. 7 )

Rhizoecus falcifer Künckel d'Herculais, 1878: 164 .

Material examined. New Zealand, Glen Eden, on roots of Helenium sp. (Asteraceae) , 25.ii.1991, N.A. Martin ( NZAC): 1/1ad ♂, in good condition.

Mounted material: macropterous, wings about equal to total body length and about a third as wide as long. Body size small, total body length about 1025 µm; antennae long, almost equal to total body length; flagellar segments of antennae either binodal or “bottle shaped”, each with long, thin fleshy setae (fs) and a few short hair-like setae (hs); body with few setae, all of moderate length, hs and robust; loculate pores (lp) large, each 10–12 µm wide, with 6–9 loculi; small simple pores apparently absent but minute sclerotised pores (msp) frequent on thorax and abdomen. Legs well developed; each trochanter with a strong Y-shaped sclerotisation and 3 pairs of campaniform pores.

Head: about 100 µm long; apparently extending further posteriorly on dorsal surface than ventrally; greatest width about 150 µm. Dorsal epicranium lightly sclerotised throughout; with (on each side) 8 or 9 hs dorsal head setae (dhs), each about 33–50 µm long, distributed along full length of head medially; lp absent dorsally. Ventral epicranium also lightly sclerotised; with a short ventral midcranial (vmcr) and lateral midcranial ridges (lmcr) anteriorly; with 6 ventral midcranial ridge setae (vmcrs) on each side, similar to those dorsally, + a pair of lp (each about 9 µm wide, with possibly 6 loculi); no setae present laterad or posterior to ventral eyes. Eyes: ventral eyes (vse) larger (each about 38 µm wide) than dorsal eyes (dse) (each about 29–32 µm wide). Ocular sclerite not differentiated from rest of epicranium but lightly sclerotised. Preocular ridge (procr) restricted dorsally to a small sclerotisation laterad to each scape; ventrally, procr represented by narrow ridges which appear to fuse medially.

Antennae: 10-segmented; about 935 µm long (ratio of total body length to antennal length 1:0.91). Scape (scp) squarish, each about 48 µm long, 53 µm wide, with 4 hs. Pedicel (pdc) each about 50 µm long, 35 µm wide; with about 9 fs (each about 55–60 µm long), 3 hs (about 33 µm long), mainly on ventral surface, + 1 campaniform pore on dorsal surface. Segments III–VI elongate and binodal, each node with a ring of fs; segments VII–IX bottleshaped, with neck at distal end; also with 2 (less clear) rings of fs; approximate lengths of segments (µm): III: 108; IV: 113; V: 108; VI: 108; VII: 93; VIII: 98 and IX: 84; fs each about 50–70 µm long; approximate number of setae per segment: III–VI: 7–9 fs in each ring on each node + 1 or 2 hs at distal end; segment VII–IX also with 7–9 fs in each ring but also with 2–4 hs medially + 0 or 1 hs distally; segment VIII with an antennal bristle (ab) but ab absent on IX. Segment X not constricted apically: length about 130 µm; with perhaps 32 fs, 1 hs + 3 ab; also 1 sensilla basiconica (sb) on apex.

Thorax. Prothorax: slightly swollen laterally, prothorax about as broad as mesothorax; pronotum (prn) possibly represented by a small, narrow, transverse sclerotisation medially; propleural setae (pl 1 s) probably represented on each side by about 8 robust hs, 2–4 lp and a few msp; median pronotal setae (mpns): 2 pairs of hs, 2 lp + a few msp; post-tergite (pt) absent but with 1 hs post-tergital seta (pts) in this position. With 2 antemesospiracular setae (am 2 s) on each side but no lp. Sternum (stn 1) unsclerotised, with 2 distinct sternal apophyses (st 1 a); without prosternal setae and lp. Anteprosternal setae and lp absent.

Mesothorax: prescutum (prsc) oval to rather rectangular, about 70 µm long, 100 µm wide; prescutal suture absent; with 3 pairs of hs prescutal setae (prscs). Scutum (sct): distance from prescutum to scutellum 65 µm; scutal setae (scts): 3–8 on each side; with a distinct sclerotised apodeme on anterior margin near prealare (pra); prealar ridge (prar) and triangular plate (tp) well developed. Scutellum (scl) about 90 µm wide, 42 µm long; with a distinct scutellar ridge (sclr) but no foramen; with 5 or 6 scutellar setae (scls) on each side. Postnotal apophysis (pna) unusually long. Basisternum (stn 2) about 168 µm wide, 115 µm long; bounded anteriorly by a complete, narrow marginal ridge (mr) and posteriorly by fairly strong precoxal ridges (pcr 2); with a total of 16 hs basisternal setae (stn 2 s); lateropleurite (lpl) only apparently lightly sclerotised, without an extension from marginal ridge along anterior margin; furca (f) well developed and narrow-waisted but arms no very divergent; arms extending about 3/4 way to marginal ridge anteriorly; mesoprecoxal ridge (pcr 2) with an additional narrow sclerotised ridge or fold extending ventrally from near coxal articulation. Mesothoracic spiracle (sp 2): width of peritreme 16–17 µm. Postmesospiracular setae (pm 2 s) 3 or 4 hs + 1 lp on each side posterior to each spiracle. Tegula (teg) large, without tegular setae.

Metathorax: with 2 or 3 pairs of hs metatergal setae (mts); metapostnotum (pn 3) represented by a pair of small sclerotisations. Dorsospiracular setae (dss): 2 or 3 hs + 2 lp on each side. Metepisternum (eps 3) without postmetaspiracular setae (eps 3 s); metapleural ridge (plr 3) without an additional narrow sclerotised ridge extending ventrally from near coxal articulation. Metepimeron (epm 3) sclerotised, but without setae. Antemetaspiracular setae (am 3 s) absent. Metathoracic spiracle (sp 3): width of peritreme 16–18 µm; each with 2 or 3 associated loculate pores. Metasternum (stn 3) lightly sclerotised, with 4 hs anterior metasternal setae (amss) and a pair of posterior metasternal setae (pmss) on each side; lp absent.

Wings: hyaline, about 1025 µm long and 365 µm wide (ratio of length to width 1:0.35; ratio of total body length to wing length 1:1); each wing with 2 hs alar setae (als) + 2 circular sensoria (sens) close to base of wing. Hamulohalteres absent.

Legs: metathoracic legs longest. Coxae (cx), approximate lengths: I: 99; II: 95; III: 87 µm; with about 12 hs on coxa III; long setae on each coxa not differentiated, but seta in this position about 21 µm long. Trochanter (tr) + femur (fm) length (µm): I: 210; II: 198; III: 220; trochanter III with 5 hs; each trochanter with 3 roundly oval sensoria arranged in a triangle medially and with strong, Y-shaped sclerotised ridges; long trochanter seta undifferentiated but seta in this position 26 µm long; femur III with 15 hs. Tibia (ti): I: 190; II: 173; III: 220 µm long; tibia III with a total of about 24 setae, mainly hs, becoming spur-like distally; protibia with 1 apical spur (tibs) + a long fine seta, meso- and metatibia with 2 tibs + a 3rd along ventral margin; length of longest 28–30 µm. Tarsi (ta) 2 segmented; length of both segments combined: I: 95; II: 93; III: 104 µm (ratio of length of tibia III to length of tarsus III 1:0.47); tarsus III with about 15 setae, mainly spur-like; tarsal spurs not differentiated; tarsal digitules (tdgt) long and setose, without capitate apices. Claws (c) very long and thin, without a denticle; length: III: 42 µm; claw digitules (cdt) setose, finely pointed, each 25 µm long.

Abdomen: segments I–VII: all tergites (at) and sternites (as) lightly sclerotised; pleurites on VI and VII lightly sclerotised. Loculate pores (lp) absent dorsally except on segment VIII, when 1 present on each side; 1 or 2 present pleurally on segments I and VIII; dorsal setae (ads) in lines of 4–6 robust hs on each side, each about 20–25 µm long; msp absent. Pleural setae: dorsopleural setae (dps): 1–3 hs + 1 or 2 msp on each side; ventropleural setae (vps): 2 hs + 1 or 2 msp on each side. Ventral abdominal setae (avs) (totals): II: 6; III–VII 6–9, each with 1 msp laterally on each side. Segment VIII: tergite (at) and sternite (as) distinctly sclerotised along anterior margin of penial sheath; tergite with 3 pairs of robust hs dorsal abdominal setae (ads) medially, each about 42 µm long, + 1 pair of lp; sternite with 1 pair of shorter setae but no lp; caudal extension (ce) rounded, with 1 short hs ventral pleural seta on each side plus 1 long robust seta (length 40–45 µm) in position of glandular pouches.

Genital segment: penial sheath (ps) 126 µm long, 100 µm wide at base; posteriorly narrowing rapidly to what is probably an upturned pointed apex. Anus (a) quite wide (about 25 µm); with 3 pairs of longish setae more posteriorly, each about 40 µm long. Ventrally, with a median slit-like opening through which aedeagus emerges; borders of slit lightly sclerotised; margins of ps with 2 pairs of longish setae, each 38–40 µm long, plus a pair of short setae, each about 12 µm. Aedeagus (aed) with a strong basal rod about 33 µm long; aedeagus about 105 µm long and 12 µm wide, with a sharply pointed apex, which might be membranous. Dorsally, penial sheath with a small sclerotised spine medially towards apex. Apex of penial sheath with a few small sensilla (psp).

Comment. This is the only species of Rhizoecus for which the male has been described previously ( Beardsley, 1962). Beardsley's description was quite detailed and the above description agrees reasonably closely with it. The main differences might be (character-state on present specimen in brackets): Beardsley states that (i) antennal segment II is binodose but this is clearly an error; (ii) antennal bristle present on segment IX (on segment VIII but not IX — but the distribution on the present specimen is unusual and so may be an aberration); (iii) propleural areas mildly sclerotised (appear to be entirely membranous), and (iv) prosternum weakly sclerotised (apparently membranous). Beardsley (1962) also stated that the apex of the aedeagus was bifurcated, but this was not visible on the present specimen.

Rh. falcifer and Ripersiella hibisci were the only macropterous species seen during this study. However, in many other respects Rh. falcifer and Rh. hibisci differ markedly (character-states on Rh. hibisci in brackets): (i) antennae almost as long as body (about half as long); (ii) antennal segments of several distinct shapes (antennal segments mainly barrel-shaped); (iii) head behind scapes without a constriction (constricted); (iv) head with a pair of loculate pores (lp absent on head); (v) without an obvious constriction between pro- and mesothorax (constriction distinct); (vi) prosternum possibly absent (present as a thin transverse line with 2 apophyses); (vii) lateral arms of mesofurca almost parallel (diverging strongly); (viii) loculate pores on abdomen present on segments I and VIII and mainly in pleural region (present dorsally on all segments); (ix) penial sheath more or less narrowing gradually (ps with a strong constriction about half-way along length).

Figures

FIGURE 7. Rhizoecus falcifer Künckel d’Herculais. Adult male. Where C = loculate pore; E = minute simple pore; J = dorsal view of penial sheath, K = tibio-tarsal articulation of posterior leg; L = ventral view of penial sheath, and M = claw. For other labels, see under Materials and methods: conventions.