Tropidosteptes pacificus (Van Duzee)

Aukema, Berend, Schwartz, Michael D. & Bieman, Kees Den, 2009, Tropidosteptes pacificus (Van Duzee, 1921), another Nearctic mirid in Europe (Hemiptera: Heteroptera: Miridae: Mirinae), Zootaxa 2135, pp. 65-68 : 65-68

Tropidosteptes pacificus (Van Duzee)

Neoborus amoenus: Parshley, 1921: 20 (note); Downes, 1927: 13 (list). Neoborus pacificus Van Duzee, 1921: 121 (type locality: Corvallis, Oregon, USA); Slater, 1950: 20, pl. 1, fig. 8 (female genitalia).

Tropidosteptes pacificus: Wheeler and Henry, 1974 (biology); Schwartz and Scudder, 2000: 255 (discussion); Maw et al., 2000: 14 (list).

Diagnosis. Recognized by uniform pale green to pale reddish brown coloration with dark brown spot on each callus, variable, dispersed, short dark stripes on the distal lateral portion of the femora, and “knee” spot at base of tibia, the densely punctate dorsum, especially on the periphery and midline of the frons and on the pronotum including between and anterior of the calli, the impuncate collar, and the genitalia. With European Mirini keys ( Southwood, 1959; Stichel, 1958; Wagner, 1974) it runs to the genus Camptozygum Reuter, 1896 , from which it can be easily distinguished by its coloration given above, the short distance between the calli, and the male genitalia.

Redescription. Male (Fig. 1). Coloration: Uniform pale green to pale reddish brown, sometimes with diffuse brown markings; head with apex of clypeus dark brown, sometimes more extensive mark on clypeus and centrally on mandibular plate; first antennal segment pale yellow, often with a longitudinal brown streak dorsally, sometimes brown; second segment usually all brown, third and fourth segments dark brown, narrowly pale at joints; labium pale green to pale reddish brown with apex black. Pronotum uniform pale green to pale reddish brown; each callus with central dark brown spot; collar and posterior margin pale yellow; mesoscutum pale green to pale yellow; scutellum pale green to pale yellow with side margins and tip yellowish, sometimes with diffuse brown pair of bilateral marks. Hemelytra uniform pale green to pale yellow, sometimes corium widely brown apically; membrane pale with veins pale green to pale yellow, sometimes base of anal vein and membrane distal to large areole dusky brown. Legs pale yellow; femora usually with two brown subapical bars dorsally; tibiae brown basally, often with short brown dash dorsally in basal half; last tarsomere apically dark brown. Venter pale green to pale reddish brown; thoracic pleura dorsally reddish brown to brown. Surface and vestiture: Dorsum closely and coarsely

punctate; with dense, short, golden, decumbent vestiture;

antennal segment I glabrous, other segments with both short

and long semidecumbent setae. Head ventral to antennal

insertion, frons laterally, and temporal areas smooth,

otherwise closely punctate. Pronotum strongly punctate;

punctate between calli and collar; calli and collar

impunctate; scutellum closely punctate with apex less

punctate; hemelytra strongly punctate. Structure:

Moderately large, obovate. Head short and vertical,

transverse basal carina distinct; eyes large and prominent,

projecting well beyond pronotal anterior angle; antennal

segment about half width of scutellum, antennal segment I

slender; labium reaching to hind coxae, first segment

swollen. Pronotum trapeziform, collar prominent, lateral

margins of pronotum rounded or carinate; ostiolar peritreme

large. Male genitalia (Figs 2–5): genital segment without

tubercles dorsal to paramere insertions; phallotheca with

well sclerotized, prominent flange projection from right

dorsal margin; endosoma with ductus seminis expanded

subdistally, secondary gonopore wide, oval, large trough

distal to secondary gonopore deep and forming apex of

broad basal process left of secondary gonopore; spinose

spicule right of secondary gonopore, straight and longer

than membrane; left paramere sparsely setose, sensory lobe

moderately prominent, steep-sided, apex narrow pointed;

right paramere elongate, slightly thickened medially, apex

small, glaborous.

Measurements: (n = 2; average and range in mm): Total

length 4.75 (4.30–5.10); width 1.84 (1.73–2.00). Head

width 1.05 (1.00–1.07); vertex width 0.45 (0.42–0.48).

Length of antennal segment I, 0.41 (0.37–0.47); II, 1.10

(1.00–1.38); III, 0.42 (0.37–0.47); IV, 0.34 (0.33–0.37).

Labium length 1.43 (1.35–1.53). Pronotal width 1.67

(1.53–1.77). Note: measurements of the two males collected FIGURE 1. Dorsal habitus of Tropidosteptes pacificus (Van Duzee) in The Netherlands fully match these measurements. from the Netherlands (Photo: Theodoor Heijerman, Wageningen). Female: As in male except body larger, vertex wider.

Coloration: Antennal segment II yellow basally and with up to apical third dark brown. Thoracic pleura dorsally less reddish brown to brown than in male; abdominal sterna often with fuscous C–shaped marks laterally. Structure: Abdomen flattened. Female genitalia: sclerotized rings as documented in Slater (1950) for T. cardinalis Uhler ; posterior wall illustrated in Slater (1950; pl.1, fig. 8).

Measurements: (n = 10; average and range in mm): Total length 4.70 (4.40–5.80); width 2.12 (2.00–2.30). Head width 0.99 (0.97–1.02); vertex width 0.53 (0.50–0.55). Length of antennal segment I, 0.43 (0.42–0.43); II, 1.14 (1.07–1.20); III, 0.42 (0.40–0.43); IV, 0.33 (0.30–0.33). Labium length 1.35 (1.33–1.37). pronotum width 1.56 (1.50–1.60).

Specimens examined. CANADA: British Columbia: Victoria [48.43333°N 123.35°W], 10 Oct 1927, W. Downes, Fraxinus sp. ( Oleaceae ), 3Ψ(CNCI); 10 Jul 1931, W. H. A. Preece, 1♂, 5Ψ (CNC). USA: California: Alameda Co.: Oakland Hills [37.7581°N 122.1204°W], 21 May 1950, W. F. Barr, 1♂ (CNCI). Humboldt Co.: Shively [40.43083°N 123.96861°W], 19 Jun 1959, Kelton and Madge, 2Ψ (CNCI). Tuolumne Co.: Oakland Recreation Camp [38.00222°N 120.13611°W], 20 Jul 1928, R. L. Usinger, 1♂, 3Ψ (CNCI). Oregon: Benton Co.: Corvallis [44.56472°N 123.26083°W], 20 Jun 1925, W. Downes, 3Ψ; 15 May 1941, Schuh and Gray, Fraxinus sp. ( Oleaceae ), 1Ψ (CNCI). Polk Co.: Independence [44.85139°N 123.18556°W], 0 3 Jul 1934, N. P. Larson, 1Ψ (CNCI). THE NETHERLANDS: Province of Noord-Brabant: Chaam, Nature Reserve Chaamse Beek, 15 Jun 2007, K. den Bieman, Fraxinus excelsior , 1♂ (K. den Bieman); 20 Jun 2008, K. den Bieman, F. excelsior , 1♂ (B. Aukema).

FIGURES. 2–5. 2. Endosoma. 3, 4. Left paramere. 5. Right paramere, Canada.

Distribution. In North America from British Columbia south in the Pacific northwestern United States to northern California. The records from Arizona and Utah reported in Henry and Wheeler (1974) should be confirmed in light of the discussion below. Reported as introduced into Pennsylvania with nursery stock from the Pacific Northwest ( Wheeler & Henry, 1974). In Europe introduced into The Netherlands province of Noord-Brabant.

Wheeler and Henry (1974) based the distribution of T. pacificus on specimens retained in the United States National Museum. However, specimens housed in the CNCI from Arizona (Sierra Vista), California (Palo Cedro), Colorado (Colorado Nat’l. Mon.), and Durango, Mexico - which superficially resemble T. pacificus in general color and dark brown markings - are correctly identified as T. vittifrons (Knight) . The overall size of the latter species is smaller (♂: 4.20 and Ψ: 4.50 mm) and more narrow (♂: 1.65 and Ψ: 1.80 mm) than in T. pacificus ; and in the endosoma of the former species, the trough is more narrow, the basal process is smaller, and the spicule is shorter (not reaching beyond the membrane). In paratypes of T. vittifrons the frons is marked with a narrow black medial stripe, not found in the CNCI specimens nor in T. pacificus . It is our contention that the natural distribution of T. pacificus is more or less restricted to the Pacific Northwest and not in states of the intermountain west. Only reexamination of the USNM material will clarify this issue.

Biology. Collected on ash ( Fraxinus sp.) in British Columbia. Parshley (1921) and Downes (1927) reported this species as T. amoenus Reuter on poplar ( Populus sp.) and maple ( Acer sp.) trees near the docks in Victoria; this record was repeated in Henry and Wheeler (1988) and clarified by Schwartz and Scudder (2000). Found on Oregon ash ( F. latifolia Benth. ) and velvet ash ( F. velutina Torr. ) in California ( Usinger, 1945) and introduced into Pennsylvania on green ash ( F. pennsylvanica Marsh. ) ( Wheeler & Henry, 1974). Collected on European ash ( F. excelsior L.) in The Netherlands.

Tropidosteptes pacificus has two annual generations in the USA and overwinters in the egg stage. Eggs are inserted in the petioles or along the midribs of the leaves (first generation) or in the woody tissue (second generation).

Overwintered eggs hatch in late February to early March and adults mature in April. The second generation disappears in July.

The species is known as a pest of ornamental ashes in the western United States. Feeding produces distinct spotting and bleaching of foliage (foliar chlorosis), curling of leaves, and wilting of branches. Temporarily defoliation may incidentally occur when populations are large ( Usinger, 1945; Wheeler & Henry, 1974; Wheeler, 2000, 2001), but apparently ash trees usually tolerate the sucking damage ( Dreistadt, 1994).

Discussion. Tropidosteptes pacificus was collected in 2007 and 2008 on the same European ash trees in a natural environment. The origin of the introduction is not clear, but the most probable pathway seems to be as eggs in imported plant material of North American ash trees. Ornamental trees of, for instance, Fraxinus pennsylvanica , are for sale in the Netherlands, but usually grown from seed or imported from nurseries in Italy or Spain, and not imported directly from the USA or Canada. It remains to be seen if the species will spread and become a nuisance.

Acknowledgements. Natuurmonumenten gave permission for research in Nature Reseach De Chaamse Beek, and Theodoor Heijerman (Wageningen) made the habitus photo.