Mychiothrips Haga & Okajima, 2025

Okajima, Shûji & Masumoto, Masami, 2025, Some Poaceae-inhabiting Phlaeothripinae (Thysanoptera, Phlaeothripidae) in East Asia, with descriptions of six new genera and 18 new species, Zootaxa 5726 (1), pp. 1-68 : 20-21

Mychiothrips Haga & Okajima , stat. rev.

Mychiothrips Haga & Okajima, 1979: 266 . Type-species: Mychiothrips fruticola Haga & Okajima , by monotypy.

Dang et al. (2014) treated Mychiothrips as a synonym of Veerabahuthrips claiming that ‘the recorded differences between the two genera are essentially related to body size, the two species described in Mychiothrips being distinctly larger (body length 2.5mm or more) than the six species described in Veerabahuthrips (body length 2.0mm or less)’. However, this suggestion is severely lacking in scientific support, and this became clear by examining specimens added in recent years. It is not true to state that Mychiothrips is always larger than Veerabahuthrips , because the largest Veerabahuthrips (more than 2.7mm in V. longicornis ) is much larger than smallest Mychiothrips (less than 1.8mm in M. crassipes ). Moreover, there is no significant difference in the body size range of M. crassipes ( 1.75–2.80mm) and V. longicornis ( 1.85–2.75mm). It is important to note that when comparing these species, the differences between these two genera pointed out by Haga and Okajima (1979) are not all simply related to body size, and do not apply to the suggestion of Dang et al. When the latter authors claimed, ‘essentially related to body size’, it was just imagination not based on scientific observations. In Mychiothrips , for example, the fore legs exhibit extreme allometric growth especially in females. The fore femora are extremely enlarged in large individuals ( Fig. 62 ) but not enlarged in small ones ( Fig. 63 ). However, the fore tibiae of Mychiothrips are always longer and thinner than those of Veerabahuthrips , regardless of the body size (cf. Figs 62 & 63 ). Moreover, the short and heavy fore tibiae of Veerabahuthrips are heavily armed with inner distinct tubercles or projections ( Figs 64–67 ) even in small individuals, though those of Mychiothrips are not armed ( Figs 62 & 63 ) or at least armed only with a median hump and an inner subapical tubercle in large individuals. Similarly, the shapes of antennae ( Figs 75–82 ) and length of postocular setae are also not related to body size. Contrary to the suggestion of Dang et al., this is enough indication that the structural differences between these two genera are not simply related to body size, and they do not constitute a single radiation. The difference between these two genera is especially quite striking in morphological structures and movement when looking at their appearance alive. Veerabahuthrips species do not show as much allometric growth as Mychiothrips species, and regardless of body size, the armatures of the fore legs are always well developed even in small individuals. It is possible that the foreleg armatures in Veerabahuthrips are always involved in an important role, such as predation, whereas this is not so in Mychiothrips . This is because in Mychiothrips , small individuals have only vestigial armatures on the foreleg at least in M. fruticola (cf. Fig. 63 ). The genus Mychiothrips is therefore here recalled from synonymy with Veerabahuthrips , although further observations are needed, especially on feeding behavior.

Okajima (1993b) and Dang et al. (2014) suggested all eight species classified into both of these two genera inhabit bamboo. However, Veerabahuthrips species live under the leaf sheath of bamboo and feed on scale insects, at least in bambusae species-group (the two species-groups in Veerabahuthrips , the bambusae -group and the exilis - group, are recognized below as two different genera). In contrast, Mychiothrips species live on the leaf or stem of bamboo and probably prey on small arthropods other than scale insects; there is even a slight possibility that these species are phytophagous. At least Mychiothrips fruticola , the type-species of the genus known from Japan, has never been found under the sheath of bamboo, and it has not been confirmed to be predaceous, despite our extensive observations. In general, the mid and hind legs of Veerabahuthrips are somewhat short and thick relative to their body size ( Figs 57–61 ), while those of Mychiothrips are rather long and slender ( Figs 53–56 ). These morphological differences between Mychiothrips and Veerabahuthrips seem important because they are associated with different behaviors. Presumably, the short mid and hind legs of Veerabahuthrips are adapted to living in closed, narrow spaces between the leaf sheath and stem of bamboo, and since they prey on immobile scale insects they do not need to run fast. Podothrips and Okajimathrips also have similar short mid and hind legs (cf. Figs 94 & 108 ) and prey on scale insects in the narrow space under the sheath of bamboo or grass. In contrast, the long legs among Mychiothrips are possibly adapted to running fast to prey on small mobile arthropods and/or to escape from natural enemies that may be common in open spaces. These long mid and hind legs of Mychiothrips do not show size related variation, and the legs are also elongate even in small individuals.

In contrast to our observation, Ng observed in Veerabahuthrips simplex , of the exilis -group (see below), that the sharp fore femoral teeth are used to grip a leaf vein in windy conditions ( Ng & Mound 2015), but it is uncertain whether this observation was in its natural state or experimental. In our observations, Veerabahuthrips species rarely roamed freely on the leaves of bamboo. However, it is also true that Ng’s observation has an insight that cannot be ignored. Observing the fore legs of Veerabahuthrips species, it seems that when they are folded, the largest femoral tooth and the large tarsal tooth always fit well ( Figs 64–67 ), as if they are adapted to gripping something. The possibility that Veerabahuthrips species walks on bamboo leaves in rare occasions cannot be ruled out, but it is not clear because there are few observations. Otherwise, there is a slight possibility that, unlike the bambusae -group, the exilis -group may also live on bamboo leaves rather than under the leaf sheaths. However, unlike Mychiothrips which live on the leaves, the mid and hind legs of the exilis -group are short as already mentioned. In any case, further observations will be necessary to understand the behavior and life history of these thrips and to make a more accurate classification.

Veerabahuthrips contains important problems related to genus-level classification. Six species are currently listed in this genus excluding two Mychiothrips species ( Okajima 1993b, ThripsWiki 2025), and two species-groups can be recognized based on morphological differences. The bambusae -group includes four species, bambusae , clarus , longicornis and tridentatus , and the exilis -group just exilis and simplex . These latter two species have some significant morphological differences from the type of the genus, V. bambusae , and are not representative of the genus Veerabahuthrips . Members of the bambusae -group have the head elongate with a distinct preocular projection and the cheeks with a distinct constriction behind eyes ( Figs 64–67 ), whereas in exilis -group the head is smaller and not protruded anteriorly and the cheeks not constricted ( Figs 71 & 72 ). The fore tibial armatures of these two species-groups are also somewhat different. Moreover, species in the bambusae -group have the mesonotum with the median cleft almost complete (cf. Figs 69 & 70 ), though the two exilis -group species have this cleft scarcely reaching the middle ( Figs 73 & 74 ). Mychiothrips also has an incomplete median cleft like exilis -group (cf. Fig. 68 ). Although overlooked by both Haga and Okajima (1979) and Okajima (1993b), this difference is significant in considering the status of the genus. The bambusae -group can clearly be distinguished not only from exilis -group, but also from some related genera including Mychiothrips , by this structure. The complete median cleft on the mesonotum is found in a few unrelated genera within the Phlaeothripidae , such as South American Chamaeothrips and Chorithrips ( Mound 1977) , and Australian Paracholeothrips , Turmathrips and Warithrips ( Crespi et al. 2004) . As a result of these observations, the two species comprising the exilis -group are here transferred to a new genus, Takeazamiuma gen. nov. described below.

Two species are included in the genus Mychiothrips , and they can be distinguished easily from each other by the key in Okajima (1993b, P.724). There are certain Bamboosiella species with both an elongate head and enlarged fore femora, such as B. lewisi from Japan, B. magna (= magnus in the original description) from China and B. xiphiphora from Thailand, which very closely resemble Mychiothrips in appearance. These Bamboosiella species show extreme allometric growth in female as in Mychiothrips , and large females have the fore femora enlarged. Although they have unarmed fore femora, we cannot rule out the possibility that Mychiothrips is more closely related to Bamboosiella rather than Veerabahuthrips .

Figures

FIGURES62–70.Mychiothrips fruticola, head,prothorax andforeleg 62–63:(62) large female;(63)smallmale.Veerabahuthrips species, head, prothorax and fore leg, female 64–67: (64) V. bambusae; (65) V. clarus; (66) V. longicornis; (67) V. tridentatus. Mesonotum, female 68–70: (68) M. fruticola; (69) V. longicornis; (70) V. tridentatus.

FIGURES 71–82. Takeazamiuma gen. nov. species, head, prothorax and fore leg, female 71–72: (71) T.exilis comb. nov.; (72) T. simplex comb. nov. Mesonotum, female 73–74: (73) T. exilis comb. nov.; (74) T. simplex comb. nov. Antenna of Mychiothrips, Veerabahuthrips and Takeazamiuma gen. nov., female 75–82: (75) M. crassipes; (76) M. fruticola; (77) V. bambusae; (78) V. clarus; (79) V. longicornis; (80) V. tridentatus; (81) T. exilis comb. nov.; (82) T. simplex comb. nov.

FIGURES 53–61. Mychiothrips species 53–56: (53) M. crassipes, female; (54) M. fruticola, female; (55) M. fruticola, male from Honshu, Japan; (56) M. fruticola, male from Okinawa Is., the Ryukyus. Veerabahuthrips species, female 57–60: (57) V. bambusae; (58) V. clarus; (59) V. longicornis; (60) V. tridentatus. (61) Takeazamiuma exilis comb. nov.

FIGURES 94–107. Okajimathrips species. O. borealis sp. nov. 94–104: (94 & 95) whole body; (96 & 97) head; (98) mouth cone, female; (99) fore leg, female; (100) prothoracic notopleural suture, female; (101) prosternum and mesopresternum, female; (102) tube, female; (103) sternite VIII, male; (104) antennal segments III–VIII, female. O. kentingensis 105–107: (105) whole body; (106) head, female; (107) antennal segments III–VIII, female.

FIGURES 108–115. Podothrips abdominalis sp. nov. (108) whole body; (109) head and prothorax, female; (110) head, male; (111) fore tibia and tarsus, female; (112) prosternum and mesopresternum, female; (113) pelta, female; (114) tube, female; (115) antenna, female.