Myrsidea assimilis Kounek and Sychra sp. nov.

(Figs 1–2, 11, 15)

Type host: Turdus assimilis (Cabanis, 1850) —White-throated Thrush

Female (n = 3). As in Fig. 11. This species belongs to the thoracica species group sensu Clay (1966). Length of dorsal head seta (DHS) 10, 0.060; DHS 11, 0.100–0.110; ratio DHS 10/11, 0.55–0.60. Gula 4–5 setae on each side. Metasternal plate with 6–7 setae; metanotum not enlarged, with 11–12 marginal setae. Femur III with 21–25 setae in ventral setal brush.

Abdomen with tergite I enlarged, with concave lateral margins and a conspicuously convex posterior margin, with medial portion shaped as a distal narrow process (Fig. 1); tergite II with concave lateral margins and a conspicuously convex posterior margin (Fig. 1); a wide median gap in each of the tergal setae rows on segments II–VIII. Tergal setae: I, 8–10; II, 13–15; III, 15–16; IV, 18–21; V, 19–23; VI, 17–21; VII, 12–15; VIII, 8–9. Postspiracular setae extremely long (0.53–0.60) on II, IV and VIII; very long (0.40–0.45) on VII; long (0.30) on I; and short (0.14–0.20) on III; V, VI. Sternal setae: II, 3–4 in each aster, 17–18 marginal setae between asters, 9 anterior; III, 23; IV, 35–37; V, 35–38; VI, 30–32; VII, 10; VIII–IX, 22–25 including 12–14 setae on deeply serrated vulval margin; without medioanterior setae on sternites III–VII. Sternite VI slightly arched (Fig. 1). Anal fringe formed by 36–38 dorsal and 36–39 ventral setae. Dimensions: TW, 0.50–0.51; HL, 0.30–0.31; PW, 0.28–0.31; MW, 0.45–0.49; AW, 0.56–0.60; ANW, 0.23–0.24; TL, 1.50–1.56.

Male (n = 4). As in Fig. 15. Length of DHS 10, 0.060; DHS 11, 0.100–0.110; ratio DHS 10/11, 0.55–0.60. Metasternal plate with 6 setae; metanotum with 10–12 marginal setae.

Tergal setae with median gap on III–VIII tergite. Tergal setae: I, 11–12; II, 16–17; III, 17–20; IV, 19–21; V, 16–22; VI, 16–17; VII, 14–16; VIII, 8–9. Postspiracular setae extremely long (0.50–0.52) on II, IV and VIII; long (0.24–0.43) on I and VII; and short (0.13–0.18) on III, V and VI (one male with 0.23 long seta on one side of tergite VI). Sternal setae: II, 3–4 in each aster, 15–18 marginal setae between asters, 7–8 anterior; III, 22–23; IV, 35–40; V, 33–38; VI, 28–32; VII, 15–17; VIII, 7; without medioanterior setae on sternites III–VII. Genital sac sclerite swollen distally, with a subapical projection on each side, and a long darker medioposterior line (Fig. 2). Dimensions: TW, 0.44–0.46; HL, 0.29; PW, 0.28; MW, 0.38–0.39; AW, 0.47–0.48; TL, 1.26–1.33; GW, 0.11; GSL, 0.09–0.11.

Type material. Female holotype and paratype male (O.Sychra CR186) ex Turdus assimilis, COSTA RICA: Zona Protectora Las Tablas, La Amistad Lodge (8°54’N, 82°47’W; 1300 m), 21 August 2010, Sychra and Literak leg. Paratypes: 1 female and 1 male (O.Sychra CR187) with the same data as holotype, both deposited in INBio (O.Sychra CR186–187) and 1 female and 2 males with the same data as holotype, deposited in MMBC (O.Sychra CR188–189).

Remarks. Although Lindell et al. (2002) mentioned Myrsidea sp. from T. assimilis, this is the first species determination of a Myrsidea from this host. The female of M. assimilis sp. nov. is characterized by (1) the shape of tergites I–II (Fig. 1), (2) a wide median gap in rows of tergal setae on II–VIII (Fig. 1), and (3) a TW of at least 0.50. These characters place M. assimilis sp. nov. close to M. varia Ansari, 1956 (ex Turdus ignobilis debilis Hellmayr, 1902 from Peru), and M. abidae Ansari, 1956 (ex T. fumigatus aquilonalis (Cherrie, 1909) from Venezuela and the Republic of Guyana). However, the female of M. assimilis sp. nov. can easily be separated from that of M. varia by its smaller number of setae on tergite I (8–10 vs. 15) and larger number of setae on tergites IV–VII (in total 66–80 vs. 57), and from that of M. abidae by its smaller number of setae on sternites III–V (in total 93–98 vs. 109–120) and smaller dimensions, especially TW (0.50–0.51 vs. 0.54).

The male of M. assimilis sp. nov. differs from that of M. varia by its genital sac sclerite (compare Fig. 2 with fig. 73 in Clay 1966). Also, it is well characterized by the following additional features: (1) tergal chaetotaxy, and (2) sternites III–VII without anterior setae. These characters place the male of M. assimilis sp. nov. close to M. indigenella Ansari, 1956 (ex Turdus maranonicus Taczanowski, 1880 from Peru) and to M. abidae Ansari, 1956. However, the male of M. assimilis sp. nov. can be distinguished from that of M. abidae by its smaller number of setae on tergite VI (14–16 vs. 18–22) and sternite III (22–23 vs. 25–28) and from that of M. indigenella by its smaller number of setae on tergite I (11–12 vs. 14) and sternite VIII (7 vs. 10), and by larger number of setae on tergite IV (19–21 vs. 17) and tergite VII (14–16 vs. 13).

Etymology. The species name is a noun in apposition derived from the specific name of the type host.