In North America, both sexes of E. formosanus are recognized by the black head with dark metallic reflections. Females also have a light reddish brown pronotum, yellow transverse bands on terga 2, 3, 7, and 8 segments, and long and dense golden pubescence. Males also have reddish brown transverse bands on abdominal segments 2–6 and a very long flagellum (middle flagellomeres about 2.5–3.0 times as long as wide).
Body. Setae over surface clearly long and golden (Fig. C31.2); meshes of microsculpture over terga 1–8 present between pits and mostly consisting of pit-like sculpticells (surface rather matt), and meshes absent between pits on head, thorax, sterna, and terga 9 and 10.
Color. Head black with dark red purple metallic reflections. Antenna, maxillary palp and most of mandible black. Thorax black, but light reddish brown on pronotum. Fore wing lightly to darkly tinted yellowish brown (Fig. B1.25). Coxae, trochanter, femora and tarsomeres 2–5 black; tibiae and tarsomeres 1 light reddish brown in basal 0.3–0.7. Abdomen generally black, but with yellow transverse band on terga 2 and 3 along most of base and extending posteriorly to spiracle, with small yellow spot on terga 4 and 6 posterolateral to spiracle, with wide yellow transverse band on terga 7 and 8 in basal 0.5 and extending laterally posterior to spiracle (Fig. C1.40), and sterna 2–6 yellow medially. Sheath mainly dark brown to black (Fig. C1.40).
Head. Pits mostly touching but less dense on gena behind eye as a narrow transverse band, coarse over much of surface (diameter about 0.3 posterior ocellus diameter) but finer on frons and between posterior ocelli, near eye and posterior margin of vertex. Postocellar region in frontal view scarcely elevated. Antenna length clearly shorter than length of coastal cell of fore wing; flagellum widened centrally with middle flagellomeres about 1.25 times as wide as long; flagellum with 17–19 flagellomeres (Fig. B1.23), with dorsal surface of flagellomeres 1 and 2 with isodiametric meshes and flat sculpticells (thus, surface bright), bright outer surface becoming gradually narrow from flagellomeres 3 to about 7, with pegged pits on inner and dorsal surfaces from flagellomeres 3 to apex, on ventral surface from flagellomeres 1 to last one, and with setae restricted to apical margin of flagellomeres except for few setae on smooth outer surface.
Thorax. Pronotum with fine to coarse teeth over dorsal surface. Mesepisternum densely pitted (pits 0.5–1.0 pit diameter apart) and surface between pits shiny. Metatarsomere 2 with dorsal margin in lateral view straight, and about 2.0 times as long as high; tarsal pad about 0.8 times as long as ventral length of tarsomere.
Abdomen. Median basin of tergum 9 at base (length between two lateral impressions) about 0.8 times as wide as median length (Fig. B1.29). Terga 7–9 including basin densely and deeply pitted (Fig. B1.29). Tergum 10 in dorsal view about 0.7 times as long as median length of basin, with teeth over most of surface and along lateral edges (Fig. B1.29). Sheath. Apical section of sheath about 0.3 times as long as fore wing length. Ovipositor. Lancet with about 13 annuli, with visible annuli outlined only under apical section of sheath; annulus 1 weakly outlined and without pit, annuli 2–8 with pits, each pit about 0.5–0.7 times height of lancet, and about 0.3 as long as length of annulus, edge of last two annuli before teeth annuli with a wide and very shallow concavity outlined with short and sharp fold ventrally.
Color. Pronotum black. Legs black, but reddish brown on profemur and protibia, and on mesotibia and mesotarsus. Tergum 1 black, terga 2–6 or 2–7 black at base and apex but broadly reddish brown in between, terga 7 and 8 or 8 black; sterna 2–7 mainly black but yellow medially, terga 8 and 9 black.
Head. Antenna thread-like and much longer than costal cell of fore wing (Fig. C32.1); middle flagellomeres 2.5–3.0 times as long as wide.
Thorax. Metatibia in lateral view about 5.0 times as long as maximum width (Fig. C32.1), and in cross section about 1.5 times as high as maximum ventral width. Metatarsomere 1 in lateral view about 4.0 times as long as high (Fig. C32.1).
Abdomen. Sterna 2–9 completely and quite densely pitted. Apical edge of sternum 8 widely and deeply indented.
The main hosts of Eriotremex formosanus are Quercus alba, Q. laurifolia and Q. nigra (Fagaceae) and various species of Carya (Juglandaceae). Other hosts include: Liquidambar styraciflua (Hamamelidaceae), Pinus palustris, P. taeda, and P. elliottii (Pinaceae) (Smith 1996).
Based on many field-collected specimens, adults of E. formosanus are recorded basically throughout the year (except March and January) with two main flight periods, one from April to June and again from September to November (Smith 1996).
USA: AL, AR (Warrimer, 2008), FL, GA, LA, MS, NC, SC, TX (Hays Co., Buda), UT, VA. Eriotremex formosanus is known from China, Taiwan, Japan (Amami–Oshima), Vietnam, and Laos (Smith, 1981) and was accidentally introduced into southeastern United States where it is still expanding its range (Smith 1975b, Chapin and Oliver 1986, and Smith 1996). There is one record from Utah (Utah Co., Provo 40.29343°N, 111.64922°W, summer 2002, C. R. Nelson; 1 F; BYUC). It is not clear if this record is associated with lumber or represents an established population (Fig. C32.3).
Specimens studied and included for the distribution map: 26 females and 2 males from BYUC, CNC, CUCC, DEBU, FSCA, UCRC, USFS–GA, and USNM.
Specimens for molecular studies: 14 specimens. See Fig. E2.2.
USA. Arkansas: 2009, CBHR 1490, 494. Louisiana: 2005, CBHR 85, 658; 2006, CNCS 1053, 658; 2006, CNCS 1054, 658; 2006, CNCS 1056, 658. Mississippi: 1997, CBHR 4, 658; 1997, CBHR 135, 658; 2007, CBHR 1120, 658; 2007, CBHR 1121, 658; 2007, CBHR 1122, 658; 2007, CBHR 1123, 658. South Carolina: 2007, CBHR 1441, 521. Unknown State: year unknown, CBHR 145, 658; 2005, CBHR 895, 658.