Scaptococcus milleri McKenzie, 1967

Ellenrieder, Natalia Von & Watson, Gillian W., 2019, A revision of the mealybug genus Scaptococcus McKenzie (Hemiptera: Coccomorpha: Pseudococcidae), with descriptions of the adult male and female of Scaptococcus occultans sp. n. from the southwestern United States, and the male of S. milleri McKenzie, Zootaxa 4554 (2), pp. 386-400 : 388-392

Scaptococcus milleri McKenzie, 1967

( Figures 1 , 2 )

Material examined. 81 ♀♀, 1 ♂. U.S.A.: California: Imperial County : 1 adult ♀ holotype, 1 mile SW of Glamis , on crown and roots of Eriogonum deserticola , 28.i.1965, D.R. Miller, M.E. Irwin & F.D. Parker leg. [ BME]; 10

♀♀ paratypes (8 adults, 2 immatures), same data as holotype [ BME] ; 1 adult ♀ paratype, same data as holotype [ CSCA] ; 16 ♀♀ paratypes (11 adults, 5 immatures), same data as holotype but 8 miles W of Glamis , 23.xii.1965, D.R. & J.F. Miller leg. [ BME] ; 1 adult ♀ paratype, same data as holotype but 5.3 miles W of Glamis , 19.iii.1966, H.L. McKenzie leg. [ BME]. Arizona: Coconino County : 13 ♀♀ (2 adults, 11 immatures), Wahweap, on Malvaceae , 3.ix.1964, D. R. Miller & F.D. Parker leg. [ BME] ; 1 adult ♀, same data but [ USNM]. Nevada: Churchill County : 1 adult ♀, Sand Mountain , 25 miles SE Fallon, host not recorded, ii.1979, R.W. Rust leg. [ USNM] ; 1 adult ♀, same data but in sand under Ambrosia sp., 24.viii.1979 [ USNM] ; 6 ♀♀ (1 adult, 5 immatures), same data but 26.x.1979 [ USNM]; 6 immature ♀♀, same data but 2.xi.1979, on Psoralea sp. [ USNM]; 2 immature ♀♀, same data but 2.xi.1979, on Franseria sp. [ USNM]; Nye County : 16 ♀♀ (14 adults, 2 immatures), Crescent Dunes, on sand dunes, host not recorded, 18.ix.1974, F. Andrews & A. Hardy leg. [ CSCA] ; 5 adult ♀♀, same data but [ USNM]. Utah: Emery County: 9 immature ♀♀, 1 adult ♂, 17 miles N of Haksville , dunes near Glison / Butte well, host not recorded, 26.vii.1978, F. Andrews & A. Hardy leg. [ CSCA] .

Amendment to McKenzie’s 1967 adult female description. Usually the antennae are 9-segmented, but are 8- segmented in several specimens. All the specimens examined, including the holotype and paratypes, possess quinquelocular pores interspersed among the multilocular pores, which are numerous on the venter of the thorax and abdomen, and are present in low numbers on the dorsum of SV–VIII.

Immature females (second- and third-instar nymphs). The antenna is 7-segmented in second-instar nymphs, and 8-segmented in third-instar nymphs. Both instars share with the adult female the presence of anterior and posterior ostioles, a plantar denticle on the claw, trilocular pores, quinquelocular pores, modified oral collar tubular ducts, long slender setae, a circulus, and a simplified anal ring with some cellular pores forming a single row. Besides lacking a vulva, they differ from the adult female by lacking multilocular pores.

Diagnosis. Within Scaptococcus , the adult female of S. milleri can be recognized by the combination of stout legs (with prothoracic tibia + tarsus shorter than the femur) and the presence of a few dorsal multilocular and quinquelocular pores and modified oral collar tubular ducts scattered on the posterior abdominal segments (absent in S. californicus and not limited to posterior abdominal segments in S. occultans ). Female nymphs can be recognized by the presence of a circulus (absent in S. californicus ), anal ring with a single incomplete row of cellular pores (cellular pores absent in S. californicus and present in two rows in S. occultans ), and forelegs stout, with prothoracic tibia + tarsus shorter than femur (prothoracic tibia + tarsus longer than femur in S. occultans ).

Description of adult male (based on one specimen). Slide-mounted characters ( Fig. 2 ). Body of adult male elongate oval, 1,800 µm long, maximum width of mesothorax 540 µm; fleshy setae not differentiated; all setae hair-like (flagellate with acute apices, longer setae proportionally slightly thicker than shorter ones); discoidal pores and multilocular pores present, the latter mostly each with 4 loculi, a few with 5 loculi. Antenna length three quarters of body length. Males macropterous, each wing as long as total body length and 0.36 times as wide as long.

Head. Width across genae 248 µm. Each side of head with 6 pairs of dorsal setae and 2 pairs of genal setae; without dorsal multilocular or discoidal pores near each scape. Ventral head setae forming a group between each ventral eye, ocellus and base of antenna, numbering 7 on each side, accompanied by 0 or 1 multilocular and 1 or 2 discoidal pores on each side. Simple eyes round, numbering 2 pairs; dorsal eyes each about 39 µm in diameter, located approximately antero-laterally to ventral simple eyes, ventral eyes each about 54 µm in diameter. Ocular sclerites weakly sclerotized. Ocelli pronounced, situated laterally, each about 39 µm in diameter, located between preocular and post-ocular ridges. Dorsal arm of mid-cranial ridge absent, but its position indicated by a slight sclerotization. Preocular ridge well developed, extending medio-dorsally from anterior margin of dorsal simple eyes. Post-ocular ridge well developed, extending ventrally from posterior to each dorsal simple eye anterolaterally past each ocellus and extending postero-laterally to near position of mouth. Interocular ridge not detected. A short extension of the postocular ridge goes around each ocellus. Preoral ridge well developed. Cranial apophysis not detected. Ventral mid-cranial ridge short.

Antenna. Ten segmented and filiform; 1,390 µm long, 0.77 of total body length. Scape 68 µm long, with 4 setae. Pedicel 68 µm long, with 4 or 5 setae. Lengths of segments III–X (µm): III, 207; IV, 170; V, 156; VI, 165; VII, 156; VIII, 161; IX, 141; X, 97. Approximate number of setae on each of segments III–X: III 25–27; IV 25–30; V 25 or 26; VI 24–27; VII 25–27; VIII 24 or 25; IX 19–21; X 11 or 12; VIII and IX with 1 ventral antennal bristle, X with 2 subapical antennal bristles and 2 or 3 subapical sensilla basiconica; capitate, apically knobbed sensory setae absent.

Thorax. Prothorax. Pronotal ridge heavily sclerotized; pronotal sclerite represented by a subtriangular sclerotization dorsolaterally. Each side of pronotal medial area with 1 seta, 1 multilocular pore, and 0 discoidal pores; pronotal lateral area with 0 setae, 0 multilocular pores, and 1 discoidal pore; pronotal ante-spiracular area with 0 or 1 setae, and without multilocular or discoidal pores; post-tergite indistinct. Ventrally, antespiracular area on each side with 5–8 setae, 3 or 4 multilocular pores, and 0 discoidal pores. Sternum triangular, with welldeveloped transverse prosternal ridge; prosternum with 3 or 4 setae, 0 multilocular pores, and 0 or 1 discoidal pores. Anteprosternal setae absent.

Mesothorax. Prescutum oval, sclerotized, prescutal ridge well developed, prescutal suture distinct, with 3 prescutal setae on each side. Scutum sclerotized, with about 9–11 scutal setae and 3 or 4 discoidal pores on each side; prealar ridge and triangular plate well developed. Scutellum sub-rectangular, sclerotized, with 1–3 scutellar setae on each side; anterior and posterior pronotal wing processes well separated. Basisternum bounded anteriorly by a marginal ridge, posteriorly by strong precoxal ridges, median ridge absent, with 6–9 basisternal setae on each side, mainly along anterior and medial area. Lateropleurite narrow, mesepisternum and mesepimeron distinct; furca well developed, arms divergent and slightly surpassing the marginal ridge anteriorly. Subepisternal ridge long and well developed. Postalare without setae. Each side posterior to mesospiracle with 9–13 setae, 0 multilocular pores and 4 or 5 discoidal pores. Tegula present, with 3–6 tegular setae.

Metathorax. Metapostnotal sclerite and metapleural ridge well developed; precoxal ridge well developed and metasternal apophyses distinct. Metepisternum and metepimeron weakly sclerotized; postmetaspiracular area with 2–4 setae, 0 or 1 multilocular pores, and 1 discoidal pore. Metasternum membranous, on each side anterior metasternal area with 4 or 5 setae, 0 multilocular pores, 1 discoidal pore, and posterior metasternal area with 3 or 4 setae, 0 multilocular pores, and 0 or 1 discoidal pore.

Wings. Hyaline, each 1,800 µm long and 640 µm wide. Ratio of length to width 1: 0.36; ratio of total body length to wing length 1: 1; alar lobe well developed and each wing with 2 or 3 alar setae; circular sensoria not detected. Hamulohalteres each 170 µm long, with an apical hamulus 107 µm long.

Legs. Prothoracic femur robust, 263 µm long with maximum width of 73 µm, and ratio of maximum width to length 1: 3.6. Metathoracic legs (III) longest; hind femur about 292 µm; hind tibia about 438 µm; hind tarsus about 156 µm; hind tarsal claw about 58 µm. Ratio of hind femur length to hind tibia length 1: 1.5; ratio of hind tibia length to hind tarsus length 1: 0.35. Setae numbering: coxa I 7–9, II 12–14, III 11 or 12; trochanter I 3, II 4–7, III 5 or 6; femur I 30–32, II 27–34, III 38 –41; tibia I 36 –38, II 38 – 42, III 5 0–52; tarsus I 16–18, II 20– 23, III 18–20. Each trochanter with 3 campaniform sensilla arranged in a triangle medially on each side. Tibia each with 2 apical spurs. Tarsi each 2 segmented, tarsal digitules not detected. Claws each with a denticle; denticle with a broad base and sides meeting at a right angle on the prothoracic claw, and smaller, spine-like with a narrower base and acute tip on the meso-and metathoracic claws ( Fig. 2 ); claw digitules acute.

Abdomen. SI–VI: membranous except for small, slightly sclerotized abdominal tergites present laterally on SII–VI. Each segment with dorsal abdominal setae totaling SI 7; SII 11; SIII 12; SIV 11; SV 10; SVI 8; dorsal and ventral abdominal pleural setae combined and pores on each side numbering: SI 1 or 2 setae + 0 multilocular pores + 0 discoidal pores; SII 6 setae + 0 multilocular pores + 1 or 2 discoidal pores; SIII 7 setae + 2 multilocular pores + 1 or 2 discoidal pores; SIV 7 or 8 setae + 0 multilocular pores + 2 or 3 discoidal pores; SV 6 or 7 setae + 0 multilocular pores + 3 or 4 discoidal pores; SVI 6–8 setae + 0 multilocular pores + 3 or 4 discoidal pores. Ventral abdominal setae numbering: SII 4; SIII 14; SIV 11; SV 11; SVI 8. With a pair of indistinct ostioles present laterally between segments SVI and VII. SVII–VIII: membranous except for sclerotized medial tergal area on SVII and SVIII; dorsal setae on SVII numbering 7, on SVIII 2; ventral setae on SVII 5, on SVIII 0. Glandular pouches shallow, pouches on SVII each with about 20 multilocular pores spreading out around pouch, 2 or 3 discoidal pores, and 2 long glandular pouch setae, each about 209 µm long; pouches on SVIII each with about 50 multilocular pores spreading out around pouch, 0–3 discoidal pores, and 2 long glandular pouch setae, each about 317 µm long.

Genital segments. Penial sheath (comprising SIX and style) with a transverse constriction at about two-thirds of its length, 171 µm long, 100 µm wide across basal ridge, ratio of penial sheath length to width 1: 0.6. Ventrally, style approximately triangular, gradually narrowing to a narrowly rounded apex; anterior basal ridge ventrally on SIX well developed; penial sheath lacking lateral processes on either side of ventral opening; with 4–7 ventral setae on each side of SIX, 4–6 smaller ventral setae on each side of style and 4–6 sensilla near its apex. Basal rod distinct. Aedeagus 146 µm long, approximately parallel sided, ending in a pointed tip that does not extend posteriorly beyond end of penial sheath. Anus not detected.

Diagnosis. The adult male of S. milleri is diagnosed below under S. occultans .

Biology. Occurring on the crown and roots of its host and found wandering in sand dunes ( McKenzie 1967).

Hosts: Asteraceae : Ambrosia sp., Franseria sp. [new host records]; Fabaceae : Psoralea sp. [new host record]; Malvaceae [new host record]; Polygonaceae : Eriogonum deserticola .

Distribution. Arizona (Coconino County [new county record]); California (Imperial County); Nevada (Churchill and Nye Counties) [new state and county records]; Utah (Emery County) [new state and county record] ( Fig. 1 ). McKenzie (1967) mentioned Arizona as part of the distribution of S. milleri but only listed examined material from California. The specimens of this species from Arizona he referred to were deposited at BME and we provide their full locality data here.

Figures

FIGURE 1. Distribution of Scaptococcus species.

FIGURE 2. Scaptococcus milleri McKenzie. Adult male, U.S.A., Utah, Emery County, 17 miles N of Haksville, in dunes near Glison/ Butte well, deposited at CSCA.