Aphid

Capitophorus horni Börner

Capitophorus (Capitophorinus) horni Börner, 1931:129 [type: Germany, on Cirsium oleraceum; in Börner’s collection at Naumberg/Saale].

Capitophorus horni Börner.—Hille Ris Lambers, 1953:158–162.—Stroyan, 1955:292–293—Börner and Heinze, 1957: 208.—Heinze, 1961:53–54.—Heie, 1962:222.—Shaposhnikov, 1964:789.

Capitophorus horni horni Börner.—Szelegiewicz, 1964:249.—Huculak, 1965:230.

Capitophorus horni gynoxantha Hille Ris Lambers, 1953: 162 [types: Netherlands, on Cirsium oleraceum and C. arvense; in DHRL].—Eastop, 1956b:272.—Bodenheimer and Swirski, 1957:276.—Stroyan, 1964a: 79.—Achremowicz, 1967: 286.

Capitophorus gynoxantha Hille Ris Lambers.—Heinze, 1961; 53, 54.

DIAGNOSIS.—This species is easily recognized by the combination of cylindrical cornicles and 2–1–2 anterior abdominal chaetotaxy. Collections on thistles may occasionally yield C. horni mixed with the more abundant C. elaeagni, but the duplicated spinal and marginal setae are very distinctive. It may also resemble C. jopepperi, new species, but cornicles are not clavate and setae are longer and more slender in C. horni.

DESCRIPTION.—Apterous Viviparous Female (described from types of C. horni gynoxantha Hille Ris Lambers): Body stoutly spindle-shaped; pale, with tips of tibiae and entire tarsi brown, flagellum of antennae and tips of cornicles dusky in some specimens. Tergum membranous, slightly wrinkled. Head with rather poorly developed frontal tubercles; mf 1p, lf 1p, vlf 1p, df 4p, vf 2p, ac usually 1–2–1, and md 1 (sometimes 2) p; dorsal setae capitate, set on large tubercles, stalks narrowed slightly before apical knobs, subequally long but df–1 longest; ventral setae also elongate and knobbed but some pc, ac pointed. Antennal segment I strongly angular on inner apex, imbricate, bearing 2 or 3 capitate setae on projection, 2–4 more capitate hairs present on antero- and lateroventral surface, aside from usual pointed one on dorsum. A.s.II with slightly knobbed setae, 1 sometimes added. Flagellar segments imbricate, slightly dusky; a.s.IV and V subequal, about ¾ length of a.s.III; unguis averaging 5⅓ times as long as base of a.s.VI.

Thoracic and abdominal chaetotaxy as illustrated for oviparous female (Figure 81): prothorax with normal complement of 8 setae; mesothoracic to abdominal segment 5 generally 2–1–2, but mesothoracic pleurals may also be doubled and marginals single as in all other Capitophorus species; segment 6 with spinals and pleurals close at bases, setal count 2–1–1; segments 7 and 8 also with double spinals and single pleurals, approximately 2 or more marginals present, some may be pointed. Cauda stout, triangular, spiculate; with 2 or 3 lateral pairs and 5–10 smaller posterodorsal ones. Cornicles cylindrical, strongly imbricate, dusky near apices; about 2½ as long as cauda. Rostrum IV+V rather slender, tapering to a blunt point; chaetotaxy normal, i.e., 1 basal, 1 dorsal, and 3 lateral pairs of setae present, ml distinctly removed from pi pair; about l½ times length of hind tarsal segment 2.

Measurements (in mm) of 6 specimens (including 3 cotypes): BL 1.76–2.16 (1.91), We .39–.45 (.418); a.s.III .29–.35 (.323), a.s.IV .21–.28 (.242), a.s.V .21–.32 (.267), a.s.VI .09–.13 (.106) + .48–.67 (.561); cornicles .56–.64 (.598), cauda .22–.24 (.228); hind tibiae .82–1.06 (.94), hind ta–2 .08–.10 (.091), and rostrum IV+V .12–.135 (.131). Dorsal head setae .0440–.0792 mm, with following mean lengths: mf .0636, lf .0601, df–1 .0728, df–2 .0675, ipf .0625, and opf .0571. Proportions of a.s.III:IV:V, 1: .64–.84 (.75): .72–.94 (.82); VIu/VIb 4.73–5.90 (5.35); co/ca 2.54–2.78 (2.62); rostrum IV+V/ hind ta–2 1.33–1.69 (1.44).

Alate Viviparous Female (also based on C. h. gynoxantha): Head, thorax, antennae from near bases of segment III, tips of tibiae and rostrum, and entire tarsi brown; bases of legs, anterior wing margins, wing veins, abdominal sclerites, distal portions of cornicles, anal plate and cauda dusky to light brown. Head and basal antennal chaetotaxy as in aptera but dorsal head setae relatively shorter, averaging .0162 mm long; a.s.III with 21–33 (27.0), a.s.IV 12–16 (14.1), and a.s.V 1–7 (4.2) sensoria. Abdomen with setae arranged as in aptera, generally 2–1–2, but marginals sometimes 1 or 3; central sclerite not well-defined in specimens examined. Cauda tapering, slightly constricted before anterolateral pair of setae; with 5–8 setae, 2 or 3 lateral, remainder posterodorsal. Cornicles cylindrical, imbricate–spiculate; 2½ to 3¼ times as long as cauda. Rostrum IV+V as in aptera.

Measurements (in mm) of 5 cotypes: BL 1.58–1.87 (1.72), We .36–.40 (.374); a.s.III .34–.41 (.370), a.s.IV .24–.31 (.285), a.s.V .24–31 (.277), a.s.VI .10–.12 (.11) + .58–.73 (.628); cornicles .40–.48 (.436), cauda .13–.17 (.15); hind tibiae 1.01–1.08 (1.05), hind ta–2 .09–.10 (.097), and rostrum IV+V .13. Proportions of a.s.III:IV:V, 1; .67–.88 (.77): .63–.88 (.75); VIu/VIb 4.92–6.64 (5.73); co/ca 2.50–3.23 (2.92); rostrum IV+V/ hind ta–2 1.30–1.44 (1.35).

Oviparous Female: Similar to apterous vivipara except hind tibiae shorter, basally enlarged, and bearing numerous pseudosensoria; more hairy subgenital plate; unguis of a.s.VI relatively shorter.

Measurements (in mm) of 3 specimens (from Canada and Netherlands): BL 1.71–1.95 (1.81), We .38–44 (.410); a.s.III .31–.36 (.335), a.s.IV .22–.25 (.242), a.s.V .27–.29 (.277), a.s.VI .10–12 (.11) + .51–.60 (.536); cornicles .51–.62 (.562), cauda .19.21 (.203); hind tibiae .73–.89 (.81), hind ta–2 .08.10 (.09), and rostrum IV+V .12–.13 (.125); dorsal head setae .0440–.0694. Proportions of a.s.III:IV:V, 1: .64–.81 (.73): .78–.90 (.83); VIu/VIb 4.25–5.20 (4.80); co/ca 2.42–2.95 (2.77); rostrum IV+V/ hind ta–2 1.30–1.50 (1.39).

Alate Male: Similar to alate viviparous female, differing in having spinopleural sclerites of abdominal segments 3 to 5 separate, more pointed dorsal and ventral head setae, shorter cauda, and more numerous sensoria. Genitalia illustrated in Figure 100; aedeagus oblong, slightly narrowed but rounded at apex.

Measurements (in mm) of 4 specimens (from Canada and Netherlands): BL 1.37–1.46 (1.41), We .34–.38 (.35); a.s.III .35–.40 (3.66), a.s.IV .24–.28 (.273), a.s.V .23–.29 (.268), a.s.VI .12 + .50–.59 (.55); cornicles .31–.37 (.340), cauda .10–.13 (.117); hind tibiae .87–.94 (.906), hind ta–2 .08–.09 (.085), and rostrum IV+V .12–.125 (.121). Proportions of a.s.III:IV:V, 1: .63–.83 (.75): .58–.81 (.73); VIu/VIb 4.17–4.92 (4.59); co/ca 2.77–3.2 (2.93); rostrum IV+V/ hind ta–2 1.33–1.56 (1.43). Number of sensoria on a.s.III 24–43 (28.3), a.s.IV 14–15 (14.3), and a.s.V 5–10 (8.5).

HOSTS.—Holocyclic on Cirsium arvense, C. lanceolatum, C. oleraceum, and Cirsium sp.

DISTRIBUTION.—Widely distributed in Europe, with records from Denmark, Germany, Great Britain, Netherlands, Poland, and the U.S.S.R. It also occurs in Israel; it has not heretofore been recorded from North America.

SPECIMENS EXAMINED.—CANADA: Fredericton, New Brunswick, 3 ovip.f. and 2 al.m., 9–X–1964, E.MacG., on Cirsium sp. (E.MacG. coll.). UNITED STATES: Presque Isle, Maine, 3 al.v.f., 17–VII and 2–VIII–1951, G.W.S., on traps (EOE coll.); Union Gap, Washington, 1 al.v.f., 13–17–VIII–1953, E.W. Davis, on trap pans, 10 ft. level (EOE coll.). EUROPE (all in DHRL coll.): Great Britain, Anglesey, Wales, 3 apt.v.f., 8–1X–1946, F.H. Jacob, on Cirsium arvense; Netherlands, Bergen-op-Zoom, 1 apt.v.f. and 5 al.v.f., 4–VI–1942, and 2 apt.v.f., 1 ovip.f. and 2 al.m., 1–X–1941, DHRL, on C. arvense (cotypes of C. h. gynoxantha).