Hoplandrothrips Hood
Creators: name: Okajima, Shûji
name: Masumoto, Masami
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Thysanoptera
Phlaeothripidae
Hoplandrothrips

description: Hoplandrothrips Hood
Phloeothrips (Hoplandrothrips) Hood, 1912: 145. Type-species: Phloeothrips (Hoplandrothrips) xanthopus Hood (synonymised with Phloeothrips jennei Jones by Stannard, 1968), by monotypy.
Most of the members of Hoplandrothrips are fungivorous, inhabiting dead leaves and branches, under bark of dead trees, dead Palmae fronds, dead grasses or leaf-litter, although one species-group in Africa seems to be phytophagous and induce leaf galls (Mound & Marullo 1996). Currently, at least 15 species are recorded from the region between India and Japan. Nine species are recorded from Japan (Okajima 2006), eight species from China (Dang & Qiao 2014) and four species from India (Tyagi & Kumar 2016), whilst 16 species are recorded from a neighboring continent, Australia (Mound & Tree 2013). Moreover, there are at least two problems in Indian Hoplandrothrips fauna. One is H. natalensis, a bicoloured species recorded from India by Ananthakrishnan (1969) and currently placed in the genus Malacothrips (ThripsWiki 2023). It was originally described from Zululand (Trybom 1912) under the genus Hoplothrips and recorded subsequently from India based on one female and two males collected from Dehra Dun at 14.iii.1968. Although, some authors (Hood 1915; Jacot-Guillarmod 1939; Hartwig 1952; Ananthakrishnan & Sen 1980) placed this species in Hoplandrothrips, zur Strassen (1972) transferred it to Malacothrips, based on a few trivial morphological characteristics which are also found in Hoplandrothrips, and this treatment remains questionable. Hartwig (1952) described supplementarily this South African species with four fine line drawings based on the holotype male together with an additional 34 females and four males. However, these additional specimens include a different species in a series of nine females collected from Marble Hall, Transvaal (zur Strassen 1972). Judging from this description and line drawings, it seems that natalensis clearly belongs to Hoplandrothrips. Especially, some important character states of the genus Hoplandrothrips are found in the description and line drawings of the holotype male as follows: antennal segment IV with four sense cones (2 + 2), fore femur with an apical tooth, fore tibia with a sub-basal tubercle, and anteroangular pronotal setae elongate, much longer than anteromarginal setae. Moreover, there is one large male specimen in the collection of TUA identified as H. natalensis by Ananthakrishnan which could undoubtedly be included in Hoplandrothrips, not in Malacothrips. This male bears the same data as the original record from India, the morphological features are very similar to Fig. 2A in Ananthakrishnan (1969), and it presumably is one of two males recorded. It has the head with no constriction behind the eyes, maxillary stylets elongate and close together medially, fore femur enlarged with two inner apical tubercles, fore tibia with a sub-basal tubercle, and anteroangular pronotal setae elongate. These character states are shared with large males of typical Hoplandrothrips species, but this male from India has some differences from the description of holotype male in colour and structure. Therefore, this species is treated here as Hoplandrothrips natalensis (Trybom) comb. n., but the specimens identified as this species from India need to be compared again with the specimens from South Africa. The relationship between Hoplandrothrips and Malacothrips is discussed below. The other problem is in Tylothrips samirseni described from Manipur, northeastern India. The original description is somewhat defective, but the available information and illustrations provided indicate that it could well be transferred to Hoplandrothrips. In this paper, Hoplandrothrips samirseni comb. n. is newly recorded from Indonesia, Thailand and Vietnam, and details of this are discussed below under H. samirseni. In consequence, six Hoplandrothrips species are recorded from India at present time.
According to Mound and Tree (2013), among 16 Hoplandrothrips species recorded from Australia, four species have a pair of median setae on the posterior half of the metanotum, and the anterior half bears some additional small setae. However, at least all 23 species including newly described species from Southeast Asia, Taiwan and Japan, have the median pair of setae arising on the anterior half of the metanotum (cf. Figs 181 & 217), and there are no additional small setae, or with at least only one pair of small setae. Similarly, at least eight species from Australia have the fore wings parallel-sided, though all Asian species have the fore wings slightly constricted medially. Moreover, Old World Hoplandrothrips species seem to be slightly different morphologically from New World species. Most of the New World species do not have the metathoracic sternopleural sutures, whereas Old World species (at least species from Asia and Australia) usually have these sutures (Mound & Marullo 1996; Mound & Tree 2013; Okajima 2006). Mound and Tree also suggested that the large worldwide genus Hoplothrips is more closely related to Hoplandrothrips than assumed in traditional taxonomy, despite the wing forms of these two being different. This assertion is probably correct, because several character states of these genera could not be distinguished satisfactorily.Similarly, the genus Phlaeothrips and its relatives have the wings parallel-sided, although they seem to be closely related to Hoplandrothrips in which the wings are weakly constricted medially.As mentioned above, however, recent study shows the wing form of Hoplandrothrips varies from slightly constricted medially to parallel-sided. Furthermore, certain species of Hoplandrothrips unusually have a pair of long intermediate setae on tergite IX between posteromarginal setae S1 and S2. Similar long intermediate setae are commonly found in the genus Adraneothrips, and these two genera seem to be related as well. In consequence, three large genera among the Phlaeothrips -lineage, Adraneothrips, Hoplandrothrips and Hoplothrips, are unexpectedly closely related, and because these genera have comparatively few autapomorphies, distinctions between them are not always clear. Interestingly, two of these three genera, Hoplandrothrips and Hoplothrips usually show extreme allometric growth in males, although Adraneothrips do not show this kind of size-related polymorphism, and males are usually smaller with a more slender body than that of females. This difference is probably derived from differences in life strategies. Crespi (1986a, 1986 b, 1988) reported fighting between males in order to secure mating, and egg-protection by both sexes in some fungus-feeding phlaeothripine thrips including two Hoplothrips species from North America, H. karnyi and H. pedicularius, which produce large colonies and show extreme allometric growth in males. Therefore, Adraneothrips seems to adopt a different life strategy from both Hoplandrothrips and Hoplothrips.
Especially, two small sized Hoplandrothrips species from Southeast Asia, such as H. adraneoides sp. n. and H. laurencei sp. n. described below (Figs 19 & 36), are very similar to Adraneothrips in appearance. They have the head scarcely sculptured with postocular setae rather close in females (Figs 136 & 205), the fore femur and tibia unarmed even in large males (Figs 139 & 208), and the mesopresternum transverse, not divided (Fig. 209). Most likely these genera have been derived from a common ancestor and are very closely related, but Hoplandrothrips can usually be distinguished from Adraneothrips by these features: postocular setae situated near cheeks, distance between them rather variable but usually wider than 1/2 head width; maxillary stylets usually close together, sometimes narrowly separated, but usually narrower than 1/5 head width; maxillary bridge usually absent; metathoracic sternopleural sutures usually present at least in the species from Asia and Australia; fore femur frequently with inner apical tubercle(s) in male, but often absent; fore tarsal tooth always developed, but rarely absent or weakly developed in female; male sternal pore plate on abdominal segment VIII not always present. Nevertheless, Adraneothrips bellus and its related species from the New World also have the maxillary stylets close together in the middle of head, and New World Hoplandrothrips species have the metathoracic sternopleural sutures usually undeveloped. Therefore, these morphological differences do not always separate these two genera satisfactorily. However, the male of Hoplandrothrips usually shows extreme allometric growth. The major male has the prothorax well-developed with enlarged fore legs and elongate anteroangular pronotal setae, and the stout fore femora and tibiae armed frequently with inner tubercles (usually fore femur with one or two apical tubercle(s), and fore tibia with a sub-basal tubercle), whereas this kind of polymorphism is infrequently found in the genus Adraneothrips. Among 77 Adraneothrips species in the World, allometric growth or at least major males are known only from two species, A. braccatus from Australia and A. simulator from Trinidad and Costa Rica (Dang et al. 2013; Mound & Marullo 1996). One of these two species, braccatus, has the postocular setae sometimes wider apart and no male pore plate on the abdominal sternite VIII, and the generic position needs further study.
There are three grass-inhabiting Hoplandrothrips species newly described or recorded below from Southeast Asia and Taiwan. These are H. basantratus sp. n., H. graminicola sp. n. and H. samirseni comb. n., and they are presumably related to H. nobilis that is also a grass-living species recorded from Africa, India and China. They are temporarily named the nobilis -group here, and have the head elongate with a distinct constriction behind the compound eyes and the maxillary stylets narrowly separated from each other and relatively short, often not reaching the middle of the head capsule (cf. Fig. 161). Although, graminicola does not have the prosternal basantral sclerites (Fig. 201), the other two species, basantratus and samirseni, have these sclerites (Figs 167 & 239), but small or weakly developed. Using the key in Mound, Dang and Tree (2013) these two species run to the confusing genus Malacothrips, because of the presence of prosternal basantra. However, according to literature (Mound & Marullo 1996; Stannard 1968), Malacothrips at least from the New World also do not have basantral plates. In contrast, Hoplandrothrips affinis from Central and South America has the basantra weakly developed (Mound & Marullo 1996). Moreover, large males of these grass-inhabiting Hoplandrothrips have the prothorax well-developed (cf. Fig. 198) with elongate anteroangular setae, the fore legs enlarged, the fore femur with an inner apical tubercle, and the fore tibia with an inner sub-basal tubercle (cf. Fig. 164). These features derived from the allometric growth are shared with typical Hoplandrothrips species. Besides, Hoplandrothrips elongatus a grass-living species from Japan, has the head rather long and the maxillary stylets retracted scarcely to the middle of the head, but the head has no constriction behind the compound eyes, and this species is therefore somewhat intermediate. In addition, the mesopresternum of these species is divided into three sclerites (cf. Fig. 201) and very similar in form to most Hoplandrothrips species. A new species from Peninsular Malaysia, H. flavicornis sp. n., is probably related to these grass-inhabiting species, whereas it was collected from dead leafy branches.
In general appearance, the nobilis -group could not be distinguished satisfactorily from some Malacothrips species, while not all Malacothrips species appear to be congeneric with M. zonatus, the type-species described from North America (Hinds 1902; Mound & Marullo 1996; Stannard 1957, 1968). Furthermore, M. zonatus has three sense cones on antennal segment IV and the pelta trapezoidal with irregular lateral margins, but male allometric growth in this species has not been confirmed from literature including the original description. In contrast, almost all Hoplandrothrips species have four sense cones on segment IV and the pelta bell- or hat-shaped, and usually show male allometric growth. Therefore, the genus Malacothrips could be treated for the present as a distinct genus at least for zonatus, although other species listed in this genus require further detailed observation to establish their generic position. Confusing variation is reported between species in several structures, such as the shape of head and pelta, length and position of postocular setae, length and shape of maxillary stylets, and the sense cone formula on antennal segment IV. In fact, some species are very similar to the nobilis -group, and M. faurei described from Kenya, is particularly noteworthy. According to the original description (zur Strassen 1972), this bicoloured species has the head with no distinct constriction behind eyes but entirely sculptured with polygonal reticulation, the cheeks rather straight with no stout sub-basal seta, antennal segment VIII pedicellate, the pelta nearly hat-shaped with slender lateral wings, the fore tarsal tooth weakly developed in female, and male sternal pore plate on abdominal segment VIII absent. These character states are shared with Hoplandrothrips flavipes together with its related species from Asia and Australia (see flavipes -group below under H. coloratus), although M. faurei has only three sense cones on antennal segment IV. Although the presence or absence of male allometric growth in M. faurei could not be confirmed from the original description, the species appears to be somewhat intermediate between Hoplandrothrips and Malacothrips. One extreme view would be to treat these two genera together with Ecacanthothrips as a single genus. Moreover, two monobasic genera described from Brazil, Chthonothrips Hood and Schazothrips Hood (Hood 1957), are also very similar to Malacothrips and may appropriately be placed near these genera, and also require further study. Finally, an undetermined Malacothrips species from Northern Territory near Darwin, Australia, seems to be very similar to the nobilis -group (see Fig 29, in Mound et al. 2013). It has a pair of long anteroangular prothoracic setae, and closely resembles large males of both H. graminicola from Thailand and H. samirseni from India and Southeast Asia.
In this paper, 17 species are recognised in Hoplandrothrip s from Southeast Asia and Taiwan, of which 13 species are newly described and one species is newly recorded. Interestingly, the species recognised here that inhabit dead trees from tropical Southeast Asia are all rather small and feeble, mostly 1.5–2.5mm in distended body when slide-mounted, though there are some larger sized species in neighboring areas, such as H. hylaius from Australia, H. formosae sp. n. from Taiwan, H. jennyae and H. ryukyuensis from Japan, and H. sapae sp. n. from northern Vietnam. There is a possibility that the niche for larger species is occupied by Ecacanthothrips species in tropical Southeast Asia, where two or more Ecacanthothrips species are often abundant on dead leafy branches.
Diagnosis. Small to medium sized species. Usually macropterous, infrequently micropterous. Head variable in length, usually 1.0–1.5 times as long as wide, dorsal surface usually reticulate, sometimes smooth or weakly sculptured; cheeks weakly rounded, sometimes weakly or distinctly constricted behind eyes. A pair of postocular setae developed, usually situated near cheeks, often closer together in females but this distance more than 1/2 head width, rarely closer together (e.g. H. bartlei from Australia). Antennae 8-segmented, segment VIII pedicellate or conical; segment III usually with three (1 + 2), often two (1 + 1) or four (2 + 2), rarely five (2 + 3) sense cones, only one on ventral apex at most, segment IV with four sense cones. Mouth-cone long and pointed, sometimes short and rounded; maxillary stylets long, but variable in length, usually reaching postocular setae or longer, close together medially, but sometimes shorter and narrowly apart. Prothoracic notopleural sutures complete. Prosternal basantra absent, but rarely weakly present. Fore femur with one or two inner apical tubercles in male, but often absent even in large males; fore tibia with an inner sub-basal tubercle in large males, usually placed basal 1/3–2/5, but often absent (this tibial sub-basal tubercle and femoral apical tubercle(s) probably fit into each other when fore leg folded); fore tarsal tooth present in both sexes, but rarely absent or weakly developed in female. Mesopresternum usually divided into three sclerites, but often transverse, posterior margin usually narrower in male. Metathoracic sternopleural sutures usually present, but usually absent in New World species (Mound & Marullo, 1996). Fore wing usually weakly constricted medially, rarely parallel-sided, usually with duplicated cilia. Pelta usually bell-shaped, occasionally almost hat-shaped with long and slender lateral wings. Abdominal tergites II–VII each with two pairs of wing-retaining setae; tergite IX often with a pair of long intermediate setae between S1 and S2. Tube tapering, shorter than head. Terminal setae almost as long as tube or longer. Males usually show extreme allometry, with or without pore plate on abdominal sternite VIII.
description: Published as part of Okajima, Shûji & Masumoto, Masami, 2024, The genus Hoplandrothrips and its relatives (Thysanoptera: Phlaeothripidae) from Southeast Asia and Taiwan, pp. 22-91 in Zootaxa 5489 (1) on pages 33-35, DOI: 10.11646/zootaxa.5489.1.4, http://zenodo.org/record/13211341