Ethirothrips stenomelas (Walker)

Okajima, Shûji & Masumoto, Masami, 2023, Six genera of the subtribe Macrothripina from Southeast Asia to Taiwan (Thysanoptera, Phlaeothripidae, Idolothripinae), Zootaxa 5291 (1), pp. 1-74 : 51-53

Ethirothrips stenomelas (Walker)

( Figs 141–147 , 235 )

Phlaeothrips stenomelas Walker, 1859: 224 .

This species, described from Ceylon (= Sri Lanka), is widely distributed in the tropical and subtropical regions of the Old World, and has nine junior synonyms ( Mound & Palmer 1983). It may also be widely distributed in the East Asian tropics and subtropics, but may not be distributed in the temperate region. In Japan, it is known from the subtropical Ryukyu and Bonin (= Ogasawara) Islands, though it is not known from the temperate mainland, Honshu. Moreover, this species exhibits structural variation, such as the colour of fore tibiae and the length of cephalic setae such as postoculars, anteocellars, postocellars and mid-vertexals, not only between local populations but also within the same population. This wide distribution range and frequent individual variation make this species extremely difficult to define.

There is a long series of specimens from eastern Asia determined as this species in the collection of TUA, and among these we found two series of specimens which consist of unusually large sized individuals ( Fig. 148 ). E. stenomelas (including most of synonyms) are usually 3.0– 5.4mm in length (distended length on glass slides) in the female, but the specimens from Mindanao Is. of the Philippines and eastern Java are dominated by large individuals as large as 4.7–6.7mm in the female. These large individuals have conspicuously elongate antennal segment III which is usually more than 3.5 times as long as broad ( Fig. 150 ), while it is usually less than 2.8 times ( Fig. 142 ) in stenomelas . Of the specimens from Mindanao, three small individuals overlap with stenomelas in body size (4.7–5.3mm), but they also have similar elongate antennal segment III. The segment is longer than 190μm without exception, despite it is always shorter than 165μm in stenomelas . Moreover, there are the following differences in these large individuals: postocular setae closer together, situated behind inner margins of eyes; pronotum comparatively large; fore wings with more than 55 duplicated cilia; reticulation of metanotum and pelta fine and stout ( Fig. 154 ), reticles around bases of lateral wings of pelta with spinula; abdominal tergite II with more than 10 lateral setae; tube more than 4.2 times as long as broad ( Fig. 155 ). Because of these differences, we consider that it could well be treated as a distinct species. However, it could not be ruled out that these differences originate from size related variation as well as geographical variation. Therefore, further observations are required, and these populations of large body sized individuals are tentatively called E. (?) stenomelas in this paper, with description and full measurements given below.

Specimens-examined (There are numerous females and males in TUA collection, and these are a part of them).

Singapore, Macritchie Res. , 1 female, on dead branches, 8.viii.1990, TN & SO. Peninsular Malaysia, Cameron Highlands, on dead leaves and branches, 1 female and 1 male, foot of Gnung Brinchang, 26.viii.1990, 2 males, Tanah Rata, 18.ix.1990, TN & SO. Borneo, Sabah, nr. Madai Cave , 1 female, on dried twigs, 12.viii.1979, Y. Yoshikawa, Jl. Kimanis, 15km from Kimanis, 1 male, on dead leaves and branches, 9.ix.1990, TN & SO Indonesia, Java, Banyuwangi, Glemor, Tulung Rejo , Sumber Gondo , 1 female, on dead branches, 27.viii.2005, SO; Flores , Ende , on dead branches, 2 female and 1 male, Nuabosi , 23.viii.2006, Komandaru , 2 females and 1 males, 23.viii.2006, SO; Central Celebes (= Sulawesi), 18km NW from Makale , Ulu Salu , alt. about 600m, 1 male, on dead Palmae, 18.viii.1984, near Rantepao, Pedamaran, alt. about 1000m, 1 female, on dead branches, 12.viii.1984, SO. Thailand, Chanta Buri, 1 female, on dead leaves, 30.iii.1975, S. Yamaguchi; Nakornprathom , Puttamonton , 1 male, on dead branches, 18.ix.1991, P. Jangvitaya ; Saraburi, 3 females and 3 males, on dead leaves and branches, 10.ix.1991, TN & SO. Vietnam, Tuyen Quang Prov., Ham Yen Distr., Tan Lap, Lam Truong , 2 females and 1 male, 19.viii.2000; Lam Dong Prov., Finom Ward , Don Duong , 2 females and 4 males, 25.xii.2001, Dong Nai Prov., Tan Phu , Phu An , 1 male, on dead leaves and branches, 29.xii.2001, SO. Taiwan, Kaohsiung-hsien, Liukuei , 3 females and 4 males, on dead branches, 5.ix.1993, TN & SO. Japan, many females and males, see Okajima (2006) .

Figures

FIGURE 148. Ethirothrips stenomelas and E. (?) stenomelas from Mindanao, variation of body size and antennal segment III in females.

FIGURES 141–147. Ethirothrips stenomelas. (141) Head & prothorax, female; (142) antennal segments III–VIII, female; (143) tube, female; (144) metanotum & pelta, female; (145) mesopresternum, female; (146) fore tarsus, female; (147) fore tarsus, male.

FIGURES 235–246. Macrothripina genera and species. Ethirothrips species 235–243: (235) E. stenomelas, male; (236) E. (?) stenomelas, female from Mindanao; (237) E. tenuis sp. n., female; (238) E. terminalis sp. n., female; (239) E. thai sp. n., female; (240) E. tibialis, female; (241) E. tibialis, micropterous male; (242) E. tibialis, macropterous male; (243) E. virgulae, female. (244) Fernothrips femoralis gen. et sp. n., female. (245) Ischyrothrips crassus, female. (246) Polytrichothrips malayanus sp. n., female.

FIGURES 149–155. Ethirothrips (?) stenomelas from Mindanao. (149) Head & prothorax, female; (150) antennal segments II–VIII, female; (151) mesopresternum, female; (152) fore tarsus, female; (153) fore tarsus, male; (154) metanotum & pelta, female; (155) tube, female.