Chilothrips strobilus Tong and Zhang, 1994

Cui, Yanze, Xi, Jinghui & Wang, Jun, 2017, Female polymorphism in Chilothrips strobilus (Thysanoptera: Thripidae), with the first description of the male, Zootaxa 4358 (1), pp. 193-196 : 193-196

Chilothrips strobilus Tong and Zhang, 1994 ( Figs 1–14 )

Male macropterous. Body ( Fig. 1 ) yellowish brown, abdominal segments II–VI paler; antennal segment I–II yellowish brown, III brown with yellowish brown base, IV–VIII brown ( Fig. 3 ). Eyes with 6 reddish pigmented facets. Head length shorter than basal width, cheeks almost parallel, dorsum with transverse sculpture in posterior part ( Fig. 2 ); ocellar setae I and II minute, seta III arising on anterior tangent of ocellar triangle; with 5 pairs of well-developed sub-equal postocular setae. Mouth cone moderately long, not reaching anterior margin of ferna, maxillary palpi 3-segmented. Antennae ( Fig. 3 ) 8-segmented, segments III and IV with forked sense cone, VI without ventral suture. Pronotum almost smooth with one pair of well-developed posteroangular setae ( Fig. 4 ). Mesonotum sculptured with transverse striae; campaniform sensilla close to anterior margin. Metanotum surface with irregular reticulate sculpture but striate laterally. Fore and mid tibiae each with one stout seta at inner apex, hind tibiae with two stout setae. Fore wing first vein with 9–11 basal setae, one middle seta and 2 distal setae; second vein with 12–16 setae ( Fig. 7 ). Abdominal tergites with transverse sculpture, but tergites IX and X smooth; tergites II–VII with one pair of median setae, three pairs of lateral setae and one pair of posteroangular setae; tergite VIII posterior margin without comb; tergite IX with two pairs of stout thorn-like setae, setae I 2.0 times as long as II ( Fig. 6 ). Sternites II–VII posterior margin with three pairs of setae, median accessory setae absent; sternites III–VI with elliptical pore plates ( Fig. 5 ).

Measurements (in microns). Body length: 1402. Head length 129, width across eyes 134, basal width 149; eye length 58; diameter of ocelli 15; shortest distance between posterior ocelli 27; ocellar setae I–III: 7, 4, 39; postocular setae I–V: 14, 12, 16, 14, 13. Antenna length 303; antennal segments I–VIII length (width): 23(31), 47(25), 47(18), 43(17), 44(19), 54(19), 11(8), 16(6); antennal terminal seta: 25. Pronotum median length 179; width 213; posteroangular seta 74, other setae 8–23. Mesonotum median seta 17, posteromarginal seta 18. Metanotum anteromarginal seta 27, antero-median seta 17. Fore wing length 774. Abdominal tergite I median seta 18; tergite IX median setae I 27, II 13, setae S1 66, S2 110; sternites III–VI pore plate L(W): 14(20), 16(22), 15(19), 15(16).

Female macropterous. Body a little longer than male; cheeks moderately swollen, widest at base; mouth cone very long, extending beyond posterior margin of prothorax ( Fig. 8 ). Antennal segment VI ventral suture usually absent, but sometimes clear ( Fig. 14 ); Sternites II–VII with discal setae ( Figs 9–10 ); pore plates absent ( Fig. 10 ), or small and only on sternites III–IV ( Fig. 9 ). Abdominal segment X usually tube-like, but varying in shape.

Measurements (in microns). Body length 1612–1861. Female with longest tube: body length 1806, head length 161, head basal width 210; tergite X length 235, basal width 76, apical width 36 ( Fig. 11 ). Female with shortest tube: body length 1809, head length 127, head basal width 200; tergite X length 125, basal width 113, apical width 43 ( Fig. 12 ). Female with intermediate tube: body length 1861, head length 152, head basal width 183; tergite X length 202, basal width 98, apical width 38 ( Fig. 13 ).

Specimens examined (Slides mounted with Canada balsam unless otherwise noted). Holotype female, China, Liaoning Province, Xingcheng (40.6°N, 122.72°E), v.1992, from cones of Pinus tabulaeformis (Junbao Wen) , Paratypes 1 female, same data as the holotype, in the Insect Collection of South China Agricultural University ( SCAU) . 6 male, 8 female (15 male in absolute ethyl alcohol): China, Liaoning Province, Zhuanghe county, Xianrendong Natural Reserve (39.99°N, 122.96°E, asl 189 m), 6.x.2016, from litter (Jun Wang), in the Insect Collection of Jilin University (JLU).

Comments. Most species of Chilothrips are associated with Pinus flowers ( Masumoto & Okajima 2017). Females of C. strobilus were also primarily found from cones of Pinus tabulaeformis ( Tong & Zhang 1994) , but we collected abundant individuals comprising both sexes from leaf litter. In North China, these thrips would mate before cold weather, and then survive in leaf litter through the winter.

There are phenotypic differences between male and female of C. strobilus as following: (1) male with the mouth cone short, not reaching anterior margin of ferna, but female mouth cone long, extending beyond posterior margin of prothorax ( Fig. 8 ); (2) pore plates present on abdominal sternites III–VI of male ( Fig. 5 ), absent in female ( Fig. 10 ) or only with undeveloped one on sternites III–IV ( Fig. 9 ); (3) discal setae on abdominal sternites absent in male but present in female; (4) two pairs of stout thorn-like setae on abdominal tergite IX present in male ( Fig. 6 ), absent in female.

The males of Chilothrips are described in only four species, and are very similar to each other. However, the male of C. strobilus can be distinguished from the two American species, C. pini and C. occidentalis , by antennal segments I and II which is yellowish brown in pini , but brown in occidentalis ( Stannard 1973) . It is also distinguished from C. yamatensis from Japan by short mouth cone not reaching anterior margin of ferna, but yamatensis reaching the posterior margin of prothorax ( Kudô 1978).

Chilothrips species are characterised in females by the tube-like form of abdominal segment X, but the shape of this segment is variable among females of C. strobilus ( Figs 11–13 ). Moreover, the ventral suture on antennal segment VI is either present or absent ( Fig. 14 ), a condition shared with C. yamatensis . In females of C. strobilus , pore plates are usually absent on abdominal sternites III–IV ( Fig. 10 ), but sometimes weakly developed ( Fig. 9 ). In contrast, pore plates are absent in females of C. hangzhouensis , but present on sternites III–IV in C. jiuxiensis and C. occidentalis , and present on sternites III–VI in C. yamatensis .

Figures

FIGURES 1–7. Chilothrips strobilus (male): (1) body, (2) head, (3) antenna, (4) pronotum, (5) abdominal sternites IV–V, (6) abdominal tergites IX–X, (7)fore wing.

FIGURES 8–14. Chilothrips strobilus (female): (8) ventral view of head, (9–10) abdominal sternites III & IV, (11–13) abdominal tergites IX–X,(14) antenna.