Bactrothrips idolomorphus (Karny)

Okajima, Shûji & Masumoto, Masami, 2025, Two idolothripine genera, Bactrothrips and Megalothrips (Thysanoptera, Phlaeothripidae), from Asia between India and Taiwan, with descriptions of two new species, Zootaxa 5696 (4), pp. 491-516 : 501-502

Bactrothrips idolomorphus (Karny)

(Figs 44–56)

Bactridothrips idolomorphus Karny, 1919: 117–118 .

This species was described from Perak, Peninsular Malaysia based on a unique holotype large male. It is undoubtedly closely related to B. brevitubus in having antennal segment III elongate (about three-quarters of the head length in holotype, Fig. 45) and the tubercles on tergite VI long and weakly curved inwards (Fig. 48). However, it is very difficult to define this species, because the information that can be obtained from the unmacerated male holotype specimen is limited. In particular, observation of the length of cephalic setae and the shape of the female Bournier’s Apparatus is not possible. Through the courtesy of Marianna Simões and Nikolai Ignatev of Senckenberg Forschungsinstitut und Naturmuseum, Germany, we could examine a high-quality image of the holotype male (Figs 44–48). One of the findings from the image is that the color of the mid and hind tibiae is somewhat characteristic (Figs 46 & 47). Those are largely yellow, but weakly shaded with brown sub-basally. This color pattern of tibiae is rarely found in Bactrothrips species from Southeast Asia, and there are only two females from Peninsular Malaysia which have similar color of tibiae (Figs 52 & 53) in TUA collection. These females are very similar to the holotype male in most structures, and identified them as idolomorphus in this study. Moreover, these females have two peculiar traits—the postocellar setae are much longer than both interocellar setae and postocular setae pair I, and the Bournier’ Apparatus with well-developed tufted area that is spread laterally (Fig. 55), not triangular. However, Nikolai Ignatev kindly checked the holotype male for this study, but the postocellar setae of the holotype male could not be observed. There are limitations to the discrimination of this species based on a unique male specimen that is unmacerated and unsuitable for observation. Fortunately, there are several females and males from Thailand and Vietnam listed below which may represent this species.

These females and males identified as idolomorphus in this study are probably distinct from those previously identified as the same species from Indonesia ( Java), India (Ananthakrishnan 1970 & 1973) and Sri Lanka ( Bagnall 1921, description of a synonymous species, Bactridothrips serraticornis ). Mound and Palmer published a line drawing of the head of a male from Java under the name of idolomorphus (1983, P. 152: Fig. 316). There are a good number of specimens of both sexes from Java in TUA collection which are very similar to this line drawing. The mid and hind tibiae of these specimens are sharply bicolored, unlike idolomorphus (cf. Figs 83 & 84 ). According to Ananthakrishnan and Bagnall, at least the specimens from Kerala, South India and Sri Lanka have the mid and hind tibiae sharply bicolored with brown bases and yellow apices, and indistinguishable from specimens from Java. Moreover, the Bournier’s Apparatus of the female from Java ( Fig. 88 ) is clearly different from that of idolomorphus (Fig. 55), and the postocellar setae are shorter in the specimens at least from Java and South India. Therefore, these populations may can be distinguished from idolomorphus and identified as B. serraticornis that is here recalled from synonymy. However, future research is needed to determine whether the populations from both South India and Sri Lanka are conspecific with the population from Java. In particular, the shape of the female Bournier’s Apparatus is unknown in the populations from both South India and Sri Lanka so far. Ananthakrishnan (1973) recorded idolomorphus from two somewhat isolated regions of India, Bhowali in North India and Kerala in South India, and compared these two populations. We examined one female and one male from Bhowali identified as idolomorphus by Ananthakrishnan, and they are very similar to idolomoephus from Peninsular Malaysia. Especially, this female has the mid and hind tibiae largely yellow and the postocellar setae elongate. Therefore, this female could be a true idolomorphus , but the Bournier’s Apparatus cannot be confirmed due to lack of maceration. That is, at least the population from North India is idolomorphus or may contain idolomorphus .

Bactrothrips idolomorphus is very similar to B. brevitubus from East Asia. From brevitubus , it may be distinguished by the following features: pedicels of intermediate antennal segments tinged with grayish brown (Figs 45 & 51); mid tibiae largely yellow, shaded with pale brown sub-basally (Figs 46 & 52); antennal segment III longer; postocellar setae longer than interocellar setae; female Bournier’s Apparatus with tufted area spread laterally (Fig. 55).

Diagnosis and measurements (female from Peninsular Malaysia). Distended body length 6.8–8.2 mm. Fore tibiae largely yellow, shaded with brown externally in basal half; mid and hind tibiae shaded with dark brown in basal one-third, but with extreme bases yellow (Figs 52 & 53). Antennal segment III with pedicel yellow, but scarcely shaded medially, club-head brown (Figs 45 & 51). Head widest across eyes (Figs 44, 49 & 50), 2.3–2.4 times as long as wide. Postocellar setae elongate, much longer than both interocellar setae and postocular pair I; postocular pair II almost longer than postocellar setae. Antennal segment III 0.66–0.70 times as long as head. Prothoracic pa and epim subequal in length; epim-a shorter than one-third the length of epim. Bournier’s Apparatus well-developed (Fig. 55), tufted area spread laterally, not triangular.

Measurements (female in µm). Body length about 8200 (distended). Head length 820, from anterior margin of eyes 726, width across eyes 346, maximum width across cheeks near base 290, minimum width across basal constriction 273; eyes length 230; Cephalic setae: interocellars 85–100, postocellars 130–135, postoculars pair I 80–100, postoculars pair II 170–200. Antenna total length about 2000, segments III–VIII length as follows: 570, 404, 360, 240, 108, 110. Pronotum length 330, width 520. Setae on prothorax: am 85–90, aa 75–80, ml 120–150, pa 210, epim 210, epim-a about 50–65. Pelta length 185, width 775. Tube length 1440, maximum width?.

Specimens examined. Peninsular Malaysia, 2 females, Cameron Highland, foot of Gnung Brinchang , on dead leaves and branches, 26.viii.1990, TN & SO. Thailand, 3 females and 1 male, nr. Chiang Mai, Doi Suthep , 800m alt., 7.viii.1976, SO; 1 male, data very similar to above, but 1100m alt., on dead leaves, 11.viii.1976, SO. Vietnam, 1 female, Lam Dong Province, Bao Loc, Dam Bri , on dead leaves, 28.xii.2001, SO. India, 1 female and 1 male, Bhowali (U.P.), on dry sal leaves, 18.x.1970, T. N. Ananthakrishnan.

Figures

FIGURES 79–89. Bactrothrips serraticornis from Java, Indonesia 79–88: (79) head, female; (80) head, male; (81) antennal segments III & IV, female; (82) antennal segments V–VIII, female; (83) mid tibia, femle; (84) hind tibia, female; (85) pelta, female; (86) pelta, male; (87) abdominal tubercles, male; (88) Bournier’s Apparatus, female. B. brevitubus, female: (89) Bournier’s Apparatus.