Ixodes auritulus Neumann 1904

Type-host: Unidentified bird. Other hosts: Thorn-tailed rayadito — Aphrastura spinicauda (Gmelin) (Passeriformes: Furnariidae), grass wren — Cistothorus platensis (Latham) (Passeriformes: Troglodytidae), Austral thrush — Turdus falcklandii Quoy & Gaimard (Passeriformes: Turdidae).

Description. Female [Based on 2 specimens; Figs. 4, 5.] Idiosoma (Fig. 4 A, F) of largely engorged females broadly suboval. Scutum (Fig. 4 B, C) length 1.16 – 1.22 (1.19; n = 2), width 1.00 (n = 2), ratio 1.16 – 1.22 (1.19; n = 2); lateral margins diverging for approximately 1 / 2 of scutal length, then slightly converging to broadly rounded posterior margin; lateral carinae absent; cervical grooves shallow reaching posterior quarter of scutal length; relatively sparse very fine punctations evenly distributed throughout scutum; very slight rugosity may be discernible in central field of scutum; setae (Fig. 4 B, C) relatively sparse, very short (c. 0.04 in anterolateral margin of scutum). Alloscutum (Fig. 4 A) as illustrated; setae (Fig. 4 A, D, E) numerous, evenly distributed, very short in center of alloscutum: c. 0.03 and long in area medial to marginal grooves: c. 0.09, setae in area medial to marginal grooves 3.14 – 3.67 (avg. 3.40) times longer than setae in center of alloscutum; ratio scutal length to length of setae in area medial to marginal grooves 12.55 – 13.20 (12.88; n = 2). Venter (Fig. 4 F) as illustrated; genital aperture (Fig. 4 F) medial to coxae III; genital groove (Fig. 4 F) well developed; anal groove (Fig. 4 F) oval with open posterior margin; ventral setae (Fig. 4 F) numerous, length of preanal setae c. 0.06, evenly distributed. Spiracular plates (Fig. 5 A) length 0.29 – 0.32 (0.31; n = 2), width 0.31 (n = 2), ratio 0.94 – 1.06 (1.00; n = 2); broadly suboval. Gnathosoma (Fig. 5 B – D) length from palpal apices to cornual apices dorsally 0.64 – 0.69 (0.66; n = 2), width of basis capituli dorsally 0.53 (n = 2), ratio 1.21 – 1.29 (1.25; n = 2). Dorsal basis capituli (Fig. 5 B) length from medial insertion of palpal segment I to cornual apices 0.23 (n = 2), ratio width to length 2.33 – 2.36 (2.35; n = 2), subrectangular, lateral margins slightly convex, without lateral projections, posterior margin slightly convex; cornua short, length 0.04 (n = 2), ratio total length of basis capituli, including cornua, to cornual length 6.00 (n = 2), triangular with broadly rounded apex; transversally suboval porose areas large, width 0.18 – 0.19 (0.18; n = 2), ratio width of basis capituli dorsally to width of porose area 2.83 – 3.00 (2.92; n = 2), clearly distinct, slightly indented, separated by distance of nearly 1 / 2 of their own width, openings discrete. Ventral basis capituli (Fig. 5 C, D) pentagonal; auriculae long, length 0.07 (n = 2), ratio length of gnathosoma dorsally to length of auriculae 9.38 – 10.11 (9.74; n = 2), moderately narrow, nearly twice as long as wide, directed posteriorly, with moderately broadly rounded apex. Lateral surface of basis capituli concave (Fig. 5 C, D). Palpi (Fig. 5 B, C, E) moderately long, length dorsally (segments II and III) 0.34 – 0.36 (0.35; n = 2), maximum width (in dorsolateral plane) 0.14 (n = 2), ratio 2.45 – 2.64 (2.55; n = 2), length of medial margin of palpal segment I ventrally 0.14 (n = 2); segment I with moderately long internal projection directed anteriorly and giving L-shape to segment I dorsally and ventrally; length of internal projection ventrally from base of palpal segment II to anterior apex 0.12 (n = 2), ratio combined length of palpal segments II and III to length of internal projection on palpal segment I ventrally 2.81 – 3.05 (2.93; n = 2); dorsally segment I with slight transversal ridge at base and small tapering dorsoapical denticle, mesodorsal spur indistinct; segments II and III fused with indistinct or barely discernible (mostly medially) suture between them, narrow proximally and gradually widening to broadly rounded apex. Hypostome (Fig. 5 C) length 0.37 (n = 1), width 0.14 (n = 1), ratio 2.59 (n = 1); base of hypostome nearly at same level as base of palpal segments II, club-shaped, widest close to mid-length; dental formula mostly 4 / 4, proximal rows 2 / 2 and then 3 / 3, distal rows 5 / 5; denticles sharply pointed; proximal part of hypostome without denticles moderate in length. Legs moderately long, slender. Coxae (Fig. 5 F – H): coxae I-III with internal and external spurs, coxa IV with external spur only; external spur on coxae I-IV moderately long, narrow, narrowly rounded at apex, directed posteromedially; external spur on coxa I slightly longer than those on coxae II-IV; external spur on coxae II-IV subequal in length; internal spur on coxae I-III short, nearly subequal, narrow on coxa I and broader on coxae II and III, narrowly rounded at apex; internal spur on coxa I directed slightly posteromedially; internal spur on coxae II and III directed posteriorly; external spur on coxa I at least twice as long as internal spur; no syncoxae. Distally trochanters I-IV (Fig. 5 F – H) with moderate ventral spur with narrowly rounded apex. Tarsus I length 0.71 – 0.83 (0.77; n = 2); tarsus IV length 0.65 (n = 2). Nymph [Based on 24 specimens; Figs. 6, 7.] Idiosoma (Fig. 6 C): broadly suboval, widest close to mid-length. Scutum (Fig. 6 A) length 561 – 672 (621 ± 26; n = 24), width 451 – 553 (496 ± 26; n = 24), ratio 1.15 – 1.38 (1.25 ± 0.06; n = 24); lateral margins diverging for approximately half of scutal length, then converging to broadly rounded posterior margin; posterolateral margins nearly straight; lateral carinae lacking; cervical grooves shallow; setae (Fig. 6 A) relatively sparse, short: length in posterocentral field of scutum 9 – 13 (10 ± 1; n = 15), shorter than those on alloscutum, distributed as figured. Alloscutum (Fig. 6 B) as illustrated; setae (Fig. 6 B) numerous, evenly distributed, long in center of alloscutum: 24 – 34 (26 ± 2; n = 24) and in area medial to marginal grooves: 68 – 85 (74 ± 6; n = 24), setae in area medial to marginal grooves 2.25 – 3.33 (2.83 ± 0.24; n = 24) times longer than setae in center of alloscutum; ratio scutal length to length of setae in area medial to marginal grooves 7.50 – 9.50 (8.40 ± 0.63; n = 24). Anal groove (Fig. 6 C) oval with open posterior margin; ventral setae (Fig. 6 C) numerous, evenly distributed. Spiracular plates (Fig. 6 D) length 128 – 170 (146 ± 11; n = 24), width 145 – 179 (159 ± 10; n = 24), ratio 0.83 – 1.00 (0.92 ± 0.04; n = 24), broadly oval. Gnathosoma (Fig. 7 A, B) length from palpal apices to posterior margin of basis capituli ventrally 357 – 400 (377 ± 11; n = 21), width at dorsal cornua apices 255 – 281 (266 ± 9; n = 22), ratio 1.36 – 1.50 (1.42 ± 0.04; n = 21). Basis capituli (Fig. 7 A, B): dorsally subtriangular, posterior margin slightly convex with long posterolaterally directed cornua; ventrally pentagonal; auriculae long: length 30 – 34 (34 ± 1; n = 22), ratio length of gnathosoma to length of auriculae 10.50 – 12.29 (11.17 ± 0.41; n = 21), triangular, directed posteriorly or slightly posterolaterally. Palpi (Fig. 7 A, B): elongate, length dorsally (segments II and III) 162 – 179 (171 ± 6; n = 21), width 68 – 77 (72 ± 4; n = 21), ratio 2.22 – 2.50 (2.37 ± 0.10; n = 21); segment I well developed, with relatively long internal projection directed anteriorly and giving L-shape to segment I dorsally and ventrally; length of internal projection ventrally from base of palpal segment II to anterior apex 43 – 55 (46 ± 4; n = 21), ratio combined length of palpal segments II and III to length of internal projection on palpal segment I ventrally 3.09 – 4.20 (3.70 ± 0.30; n = 21); segments II and III fused with indistinct suture between them, narrower proximally and gradually widening to broadly rounded apex. Hypostome (Fig. 7 B) length 153 – 186 (175 ± 8; n = 14), width 51 – 68 (62 ± 5; n = 14), ratio 2.62 – 3.44 (2.82 ± 0.22; n = 14); widest at approximately its mid-length; base of hypostome approximately at same level as base of palpal segment II; proximal portion of hypostome without denticles short, then dental formula 2 / 2 for approximately 3 rows and 3 / 3 for approximately 4 – 6 rows and 4 / 4 for 1 – 4 rows; apex broadly rounded with irregular smaller denticles. Legs moderately long. Coxae (Fig. 7 C): coxae I-III with well-developed internal and external spurs, coxa IV with well-developed external spur and indistinct internal spur; external spur on coxae I-IV moderately long, narrow, narrowly rounded at apex, curved slightly posteromedially; external spur on coxae I-IV nearly subequal or very slightly decreasing in size from coxa I to coxa IV; internal spur on coxae I-III short, broad and narrowly rounded at apex, shorter than external spur; no syncoxae. Trochanters I-IV (Fig. 7 C) with short ventral spur. Tarsus I length 374 – 434 (406 ± 15; n = 24); tarsus IV length 315 – 366 (334 ± 12; n = 24). Larva [Based on 35 specimens; Figs. 8, 9.] Idiosoma (Fig. 8 B): broadly suboval, widest close to mid-length. Scutum (Fig. 9 A) length 315 – 375 (349 ± 17; n = 9), width 345 – 400 (370 ± 17; n = 9), ratio 0.83 – 1.00 (0.95 ± 0.05; n = 9); hexagonal, lateral margins diverging for slightly more than 1 / 2 of scutal length, then converging to broadly rounded or nearly straight posterior margin; posterolateral margins with very slight depressions; lateral carinae absent; cervical grooves faint, shallow depressions. Setae 5 pairs, length of Sc 2 23 – 28 (25 ± 2; n = 9); length of Sc 3 24 – 28 (26 ± 1; n = 9); alloscutum (Fig. 8 A) as illustrated. Dorsal setae approximately 14 – 18 pairs; approximately 4 – 6 pairs of central dorsals, length of Cd 1 28 – 36 (33 ± 3; n = 9), length of Cd 2 26 – 34 (31 ± 3; n = 9); approximately 10 – 13 pairs of marginal dorsals combined with supplementaries, length of Md 1 35 – 43 (38 ± 3; n = 9). Venter (Fig. 8 B) as illustrated; anal groove indistinct anteriorly and open posteriorly. Ventral setae approximately 14 – 18 pairs plus 1 pair on anal valves; 3 pairs of sternals, length of St 1 29 – 38 (33 ± 3; n = 9); 2 pairs of preanals, length of Pa 1 31 – 41 (37 ± 3; n = 9), length of Pa 2 39 – 51 (46 ± 5; n = 9); approximately 6 – 10 pairs of premarginals; 3 pairs of marginal ventrals, length of Mv 1 26 – 34 (29 ± 3; n = 9). Gnathosoma (Fig. 9 B – D): length from hypostomal apex to posterior margin of basis capituli ventrally 230 – 253 (241 ± 8; n = 8), width at dorsal cornual apices 158 – 190 (173 ± 11; n = 9); ratio 1.30 – 1.53 (1.38 ± 0.07; n = 8). Basis capituli (Fig. 9 B – D): dorsally subtriangular, posterior margin slightly convex with long posterolaterally directed cornua; ventrally pentagonal with moderately long, triangular auriculae, directed posterolaterally. Post-hypostomal setae 2 pairs. Palpi (Fig. 9 B, C): elongate, length (segments II and III) 103 – 110 (107 ± 3; n = 9), width 43 – 53 (48 ± 3; n = 9), ratio 2.00 – 2.47 (2.22 ± 0.15; n = 9); segment I well developed, with moderately long internal projection directed anteriorly and giving L-shape to segment I dorsally and ventrally; length of internal projection ventrally from base of palpal segment II to anterior apex 28 – 35 (31 ± 3; n = 9), ratio combined length of palpal segments II and III to length of internal projection on palpal segment I ventrally 3.07 – 3.82 (3.50 ± 0.30; n = 9); segments II and III fused, suture between them indistinct; segment I lacking setae, 10 dorsal and 3 ventral setae on segments II and III combined. Hypostome (Fig. 9 C): length 98 – 105 (101 ± 3; n = 8), width 45 – 53 (46 ± 3; n = 8), ratio 2.00 – 2.28 (2.19 ± 0.09; n = 8); base of hypostome nearly at same level as articulation of palpal segments I and II; proximal portion without denticles short, then dental formula 1 / 1 for 1 row, 2 / 2 for approximately 3 or 4 rows and 3 / 3 for approximately 4 – 6 rows; apex broadly rounded with irregular small denticles. Legs moderately long. Coxae (Fig. 9 E): coxa I with well-developed internal and external spurs, coxae II and III each with well-developed external spur and indistinct internal spur; external spur on coxae I-III moderately long, narrow, narrowly rounded at apex, curved slightly posteromedially; external spur on coxae I-III nearly subequal and usually decreasing slightly in size from coxa I to coxa III; internal spur on coxae I moderately long, broad and narrowly rounded at apex, usually slightly shorter than external spur; posteromedian angle of coxa II forming slight, broadly rounded projection; no syncoxae; coxae I and III with 3 setae each, coxa II with 2 setae. Trochanters I and II with short ventral spur; trochanter III lack of ventral spur (Fig. 9 E). Tarsus I length 230 – 248 (237 ± 7; n = 9); tarsus III length 205 – 221 (214 ± 5; n = 9).

The female of I. auritulus can be distinguished from the female of I. cornuae by having short cornua (vs very long cornua in that species); from females of I. kerguelenensis and I. percavatus by having the indistinct mesodorsal spur on palpal segment I (vs large, distinct spur in those species); and from the female of I. paranaensis by having longer auriculae (vs very short auriculae in that species) (see Arthur 1960; Wilson 1970; Barros-Battesti et al. 2003). The female of I. auritulus can be distinguished from females of other species by the broad scutum: mean ratio length to width 1.19 (vs narrower scutum: mean ratio 1.44 in I. brevisetosus n. sp., 1.45 in I. contrarius n. sp., 1.35 in I. insulae n. sp., 1.41 in I. rio n. sp. and 1.37 in I. zealandicus); short setae in center of alloscutum and long setae in alloscutal area medial to marginal grooves: mean ratio length of setae in alloscutal area medial to marginal grooves to length of setae in center of alloscutum 3.40 (vs longer setae in both center and area medial to marginal grooves of alloscutum: mean ratio 1.09 in I. guglielmonei n. sp., 2.00 in I. insulae n. sp. and 1.14 in I. zealandicus; shorter setae in alloscutal area medial to marginal grooves: mean ratio 1.58 in I. brevisetosus n. sp., 2.65 in I. robbinsi n. sp. and 2.73 in I. tinamou n. sp.); long setae of alloscutum medial to marginal grooves: mean ratio length of scutum to length of alloscutal setae medial to marginal grooves 12.88 (vs shorter setae of alloscutum medial to marginal grooves: mean ratio 45.62 in I. brevisetosus n. sp., 20.89 in I. moralesi n. sp., 26.93 in I. robbinsi n. sp. and 17.40 in I. tinamou n. sp.); broad gnathosoma: mean ratio length of gnathosoma to width of basis capituli 1.25 (vs narrower gnathosoma: mean ratio 1.33 in I. brevisetosus n. sp. and I. zealandicus and 1.34 in I. insulae n. sp.); basis capituli slightly convex dorsolaterally (vs basis capituli with angular dorsolateral projections in I. brevisetosus n. sp. and I. rio n. sp.); lateral surface of basis capituli concave (vs lateral surface flat in I. brevisetosus n. sp.); posterior margin of basis capituli slightly convex (vs sinuously concave in I. guglielmonei n. sp. and straight to very slightly concave in I. zealandicus); moderately long cornua: mean ratio length of basis capituli to cornual length 6.00 (vs longer cornua: mean ratio 4.94 in I. guglielmonei n. sp. and 4.60 in I. insulae n. sp.; shorter cornua: mean ratio 14.00 in I. contrarius n. sp., 10.00 in I. rio n. sp. and 9.92 in I. tinamou n. sp.); broad porose areas: mean ratio width of basis capituli to width of porose area 2.92 (vs narrower porose areas: mean ratio 3.61 in I. brevisetosus n. sp. and 3.47 in I. rio n. sp.); auriculae long: mean ratio length of gnathosoma dorsally to length of auriculae 9.74, moderately narrow, directed posteriorly, with moderately broadly rounded apex (vs shorter auriculae: mean ratio 28.15 in I. guglielmonei n. sp., 14.59 in I. robbinsi n. sp., 40.07 in I. tinamou n. sp. and 19.54 in I. zealandicus; auriculae distinctly broader, with broader rounded apex in I. guglielmonei n. sp., I. moralesi n. sp., I. robbinsi n. sp., I. tinamou n. sp. and I. zealandicus; auriculae directed slightly outwards in I. guglielmonei n. sp., I. tinamou n. sp. and I. zealandicus); moderately long internal projection on palpal segment I: mean ratio length of palpal segments II and III to length of projection on palpal segment I 2.93 (vs longer projection: mean ratio 1.88 in I. contrarius n. sp.; shorter projection: mean ratio 4.94 in I. guglielmonei n. sp., 3.55 in I. insulae n. sp., 3.57 in I. tinamou n. sp. and 4.50 in I. zealandicus); lack of spur at base of palpal segment I dorsally (vs short mesodorsal spur at base of palpal segment I dorsally in I. insulae n. sp., I. moralesi n. sp. and I. zealandicus); moderate dorsoapical spur on palpal segment I (vs indistinct spur in I. contrarius n. sp., I. guglielmonei n. sp., I. rio n. sp., I. robbinsi n. sp. and I. tinamou n. sp.; large, hook-like spur in I. moralesi n. sp.); moderately narrow palpal segments II and III: mean ratio length to width 2.55 (vs narrower segments: mean ratio 2.82 in I. brevisetosus n. sp.; broader segments: mean ratio 2.16 in I. guglielmonei n. sp.); external spur on coxae I-IV relatively long, narrow, sharper at apex (vs shorter, broader spur with broadly rounded apex in I. tinamou n. sp. and I. zealandicus); generally moderately large species: see description for measurements (vs noticeably smaller species: I. contrarius n. sp.; noticeably larger species: I. guglielmonei n. sp., I. insulae n. sp. and I. moralesi n. sp. See descriptions for measurements). The nymph of I. auritulus can be distinguished from nymphs of I. brevisetosus n. sp., I. guglielmonei n. sp., I. robbinsi n. sp. and I. tinamou n. sp. by its relatively short and narrow scutum (vs longer and broader scutum in I. guglielmonei n. sp.; broader scutum in I. robbinsi n. sp. and I. tinamou n. sp.), shorter setae in posterocentral field of scutum (vs longer setae in I. guglielmonei n. sp.), long setae on alloscutum in area medial to marginal grooves (vs shorter setae in I. brevisetosus n. sp., I. robbinsi n. sp. and I. tinamou n. sp.), moderately long setae in center of alloscutum (vs shorter setae in I. brevisetosus n. sp., I. robbinsi n. sp. and I. tinamou n. sp.; longer setae in I. guglielmonei n. sp.), setae on alloscutum in area medial to marginal grooves at least twice longer than setae in center of alloscutum (vs subequal setae in I. guglielmonei n. sp.), relatively long and moderately broad spiracular plate (vs broader spiracular plate in I. guglielmonei n. sp.; shorter and narrower spiracular plate in I. tinamou n. sp.), relatively short and narrow gnathosoma (vs longer and broader gnathosoma in I. guglielmonei n. sp.; broader gnathosoma in I. tinamou n. sp.), moderately long auriculae (vs longer auriculae in I. brevisetosus n. sp.; shorter auriculae in I. guglielmonei n. sp., I. robbinsi n. sp. and I. tinamou n. sp.), relatively short and narrow palpal segments II and III (vs longer and broader segments in I. guglielmonei n. sp.; broader segments in I. robbinsi n. sp. and I. tinamou n. sp.), relatively long internal projection on palpal segment I (vs shorter projection in I. guglielmonei n. sp.), relatively short and narrow hypostome (vs broader hypostome in I. brevisetosus n. sp. and I. robbinsi n. sp.; longer and broader hypostome in I. guglielmonei n. sp.), relatively short tarsus I (vs longer tarsus in I. guglielmonei n. sp., I. robbinsi n. sp. and I. tinamou n. sp.) and relatively short tarsus IV (vs longer tarsus in I. guglielmonei n. sp., I. robbinsi n. sp. and I. tinamou n. sp.). The larva of I. auritulus can be distinguished from larvae of I. brevisetosus n. sp., I. guglielmonei n. sp. and I. robbinsi n. sp. by the broadly rounded posterior margin of scutum (vs straighter margin in I guglielmonei n. sp.); distinctly sculptured surface of scutum (vs sculpture of scutum usually poorly distinct in I. brevisetosus n. sp.); smaller dimensions of the following characters: width of scutum, length of gnathosoma, length and width of palpal segments II and III, length and width of hypostome, length of tarsi I and III (vs longer hypostome in I. brevisetosus n. sp.; larger size of the characters listed in I. guglielmonei n. sp.); longer setae Sc 2, Sc 3, Cd 2, Md 1, Pm 1 and Mv 1 (vs these setae shorter in I. brevisetosus n. sp. and I. robbinsi n. sp.); moderately long setae Cd 1 (vs shorter setae in I. brevisetosus n. sp. and I. robbinsi n. sp.; longer setae in I. guglielmonei n. sp.); longer setae St 1 (vs shorter setae in I. robbinsi n. sp.); moderately long setae Pa 1 (vs longer setae in I. guglielmonei n. sp.; shorter setae in I. robbinsi n. sp.); longer setae Pa 2 (vs shorter setae in I. robbinsi n. sp.); longer auriculae (vs shorter auriculae in I. guglielmonei n. sp. and I. robbinsi n. sp.); long anterior projection on palpal segment I (vs shorter projection in all other species) and poorly distinct internal spur on coxa II (vs well-developed spur in I. guglielmonei n. sp.).

Remarks. Neumann (1899) based his description on 4 females collected at Punta Arenas, Magallanes Province, Chile. According to Arthur (1960) three of those females are in the collection of the Muséum national d’Histoire naturelle, Paris, France and one female is at École Nationale de Vétérinaire, Toulouse, France. Unfortunately, we were unable to confirm if any of these specimens currently exist. The association of the I. auritulus female specimens we studied with the type specimens was made by analysis of the description of the latter in Arthur (1960). All the available characters as well as most of the morphometrics taken from the Arthur’s illustrations unambiguously confirmed our identification of I. auritulus. We conclude that the male of I. auritulus is undescribed. Previous descriptions of males refer either to other species (Dumbleton 1953, 1961; Gregson 1956; Arthur 1960; Wilson 1967) or to undetermined species of the I. auritulus complex (Kohls & Clifford 1966; Keirans & Clifford 1978; Furman & Loomis 1984; Onofrio et al. 2009; Lindquist et al. 2016; Nava et al. 2017). Whether any of the latter descriptions refer to true I. auritulus is yet to be determined, if possible, at all. The female of I. auritulus was described in Neumann (1899, 1904, 1911), Nuttall and Warburton (1911) and Arthur (1960). Illustrations of the female in Wilson (1967) are based on Arthur (1960) and hence Wilson’s description, is at least, partially based on I. auritulus. All other previous descriptions of females either refer entirely or partially to other species (Nuttall 1916; Cooley & Kohls 1945; Dumbleton 1953, 1961; Gregson 1956; Roberts 1970; Keirans & Clifford 1978; Furman & Loomis 1984; Barros-Battesti et al. 2003; Onofrio et al. 2009; Lindquist et al. 2016; Bermúdez et al. 2018) or to undetermined species of the I. auritulus complex (Ault 1943; Nava et al. 2017). The description of the nymph of I. auritulus in Durden and Keirans (1996) was partially based on specimens of true I. auritulus and those of I. guglielmonei n. sp. All other previous descriptions of nymphs either refer entirely or partially to other species (Nuttall 1916; Cooley & Kohls 1945; Dumbleton 1953; Gregson 1956; Arthur 1960; Roberts 1970; Furman & Loomis 1984; Lindquist et al. 2016) or to undetermined species of the I. auritulus complex (Aragão 1938; Ault 1943; Wilson 1967; Nava et al. 2017). Apparently, most of the larval description in Webb et al. (1990) was based on true I. auritulus specimens, and partially on I. robbinsi n. sp. All other previous descriptions of larvae either refer entirely or partially to other species (Nuttall 1916; Dumbleton 1953; Furman & Loomis 1984; Lindquist et al. 2016) or to undetermined species of the I. auritulus complex (Wilson 1967). By having a distinct, anteriorly directed internal projection on palpal segment I, the female of I. auritulus most closely resembles the following Ixodes (Multidentatus) spp.: I. brevisetosus n. sp., I. contrarius n. sp., I. cornuae, I. guglielmonei n. sp., I. insulae n. sp., I. kerguelenensis, I. moralesi n. sp., I. paranaensis, I. percavatus, I. rio n. sp., I. robbinsi n. sp., I. tinamou n. sp. and I. zealandicus.

Etymology: The specific name is derived from the Latin auritus meaning “ having ears ” and suffix - ulus meaning “ small ” apparently referring to palpal segment I having a distinct anterior projection.

Type-locality: Chile: Magallanes Province: Punta Arenas. Other localities: Chile: Antártica Chilena Province: Isla Navarino, Puerto Williams; Magallanes Province: Fuerte Bulnes. Type-material: 4 syntype females, Punta Arenas (~ 53 ° 8 ’ S, 70 ° 55 ’ W), Magallanes Province, Chile, Lebrun; deposited in the Muséum national d’Histoire naturelle, Paris, France (3 females: No. 2474 – 83) and École Nationale de Vétérinaire, Toulouse, France (1 female), according to Arthur (1960), who mentioned that these four specimens were badly mutilated. We were not able to confirm the existence of these specimens. Other material: Two females, 24 nymphs and 35 larvae. Chile: Antártica Chilena Province: Isla Navarino (~ 55 ° 4 ’ S, 67 ° 40 ’ W): 1 female, from T. falcklandii, 19. i. 1964, G. E. Watson (GEW), USNMENT 00987234; Isla Navarino, Puerto Williams (~ 54 ° 55 ’ S, 67 ° 37 ’ W): 1 nymph and 3 larvae, from T. falcklandii, 2. ii. 1964, GEW, USNMENT 00987156; same locality: 1 nymph and 2 larvae, from A. spinicauda, 2. ii. 1964, GEW, USNMENT 00987173; Magallanes Province: Fuerte Bulnes (~ 53 ° 36 ’ S, 70 ° 55 ’ W): 2 nymphs and 7 larvae, from A. spinicauda, 17. iv. 1971, USNMENT 00987185; same locality: 1 nymph, from A. spinicauda, 17. iv. 1971, USNMENT 00987175; same locality: 1 larva, from A. spinicauda, 17. iv. 1971, USNMENT 00987194; same locality: 1 nymph, from A. spinicauda, 17. iv. 1971, USNMENT 00987193; same locality: 1 larva, from A. spinicauda, 17. iv. 1971, USNMENT 00987183; same locality: 2 nymphs and 2 larvae, from A. spinicauda, 17. iv. 1971, USNMENT 00987160; same locality: 2 nymphs, from A. spinicauda, 17. iv. 1971, USNMENT 00987182; same locality: 2 nymphs and 1 larva, from A. spinicauda, 17. iv. 1971, USNMENT 00987171; same locality: 1 nymph and 7 larvae, from A. spinicauda, 17. iv. 1971, USNMENT 00987190; same locality: 1 larva, from A. spinicauda, 17. iv. 1971, USNMENT 00987179; same locality: 1 nymph, from A. spinicauda, 17. iv. 1971, USNMENT 00987145; same locality: 1 nymph, from A. spinicauda, 17. iv. 1971, USNMENT 00987170; same locality: 1 nymph and 3 larvae, from A. spinicauda, 17. iv. 1971, USNMENT 00987178; same locality: 2 nymphs and 4 larvae, from A. spinicauda, 17. iv. 1971, USNMENT 00987146; same locality: 4 nymphs and 3 larvae, from A. spinicauda, 17. iv. 1971, USNMENT 00987186; Punta Arenas: 1 female and 1 nymph, from C. platensis, 16. i. 1940, C. C. Sanborn, FMNH 4463077; same locality: 1 nymph, from A. spinicauda, 15. iv. 1971, USNMENT 00987165. All specimens with USNMENT numbers are deposited in the USNTC, and the specimens with a FMNH number are deposited in the FMNH.