Hoplothrips dubius (Bagnall)

Mound, Laurence A., 2017, Intra-specific structural variation among Hawaiian Hoplothrips (Thysanoptera, Phlaeothripidae), with ten new synonymies and one new species, ZooKeys 722, pp. 137-152 : 140

Hoplothrips dubius (Bagnall)

Dolerothrips dubius Bagnall, 1910: 691

Dolerothrips barbatus Bagnall, 1910: 683. Syn. n.

Dolerothrips ovatus Bagnall, 1910: 686. Syn. n.

Dolerothrips angusticeps Bagnall, 1910: 688. Syn. n.

Dolerothrips bicolor Bagnall, 1910: 688. Syn. n.

Hoplothrips coprosmae Moulton, 1936: 186. Syn. n.

Remarks.

This species is a member of the Hoplothrips fungi complex. This comprises corticis, fungi , japonicus, karnyi , orientalis and ulmi, and Stannard (1968: 459) suggested that these various names may refer to a single species that is widespread across the Holarctic; Schliephake and Klimt (1979) even placed fungi as a synonym of ulmi. However, as indicated below, each of these six species can, at present, be distinguished from the others. In contrast, dubius from the Hawaiian Islands cannot be distinguished satisfactorily from some individuals identified as karnyi from North America, including from Vancouver, Canada. In the absence of more extensive studies on the Hoplothrips fauna of Western North America, the name dubius seems appropriate to use for the form on Hawaii. Currently, the six species in the fungi complex are distinguished from each other as follows. Specimens with antennal segment IV brown are placed in orientalis, the other five all having antennal segments IV–V yellow at the base. The males of fungi share with those of japonicus and orientalis a particularly large pore plate on sternite VIII, but fungi is distinguished by having long slender sense cones on antennal segment III, particularly the one on the inner apical margin. According to Okajima (2006), japonicus has antennal segment III particularly elongate, more than 2.6 times as long as wide, although the sense cones on that segment are as short as in ulmi; in orientalis, these sense cones are intermediate in length between fungi and ulmi. Finally, ulmi has short sense cones on antennal segment III, and the median length of the pore plate on sternite VIII of males is much shorter than in fungi ( Mound et al. 1976; Okajima 2006). Specimens identified as the North American species, karnyi , have the short antennal sense cones of ulmi, but the pore plate on sternite VIII of males is variable and intermediate between the condition found in fungi and ulmi from Europe The species here identified as dubius was found quite commonly on Hawaii, in Volcano National Park, in June 2016, and also at two sites on Oahu - Makuleia trail and Manoa Cliffs trail.

Bagnall described dubius from five winged females and one “aptera”, taken variously on the three islands - Hawaii, Molokai and Lanai. However, only the macropterous female from "Molokai Mts" remains, and this has only one antenna (Fig. 14) and is slide mounted and designated lectotype ( Mound 1968). The unique holotype of barbatus , a large micropterous male from Kona, Hawaii, was described as lacking the distal antennal segments, although segments III and IV are available and are brown with the basal third yellow. Sternites III–VII have paired reticulate areas similar to those illustrated on the male syntype of flavipes (Fig. 22), and the median length of the pore plate on sternite VIII is about 30 microns. The lectotype of ovatus is the single large male that was taken on Haleakala, Maui, but of the original six females mentioned by Bagnall only two remain. The three specimens were slide mounted in 1967, and they retain antennae and most setae, but there is no reason to consider this as a different species from dubius . Antennae were not available on either of the two original specimens of angusticeps , and the lectotype is the male from Kalae, Molokai. Although much smaller than the barbatus holotype, it falls within the size range expected in species of Hoplothrips and has reticulate areas laterally on the sternites, and the pore plate on sternite VIII is about 40 microns long medially. Bagnall described bicolor from a single female taken on Kaala, Oahu. This lacked antennae, and the specimen is now slide mounted and lacks all major setae except for a single lateral seta on the third tergite; contrary to the original description, the tube is no paler than in other specimens here identified as dubius . Moulton based coprosmae on four females and six males from Nauhi, Hawaii. These specimens are in good condition, and they have been compared with macropterous and micropterous specimens of both sexes collected on Hawaii and Oahu in June 2016, all of which have variably prominent cheek setae on the head. The antennal sense cones are not as elongate as in fungi from Europe, and in males the sternites have reticulate areas laterally and the pore plate on sternite VIII is about 35 microns long medially. If these recent specimens, also the coprosmae types, had been collected in North America they would have been identified as karnyi . However, as indicated above, it is not possible at present to establish further synonymies between the fauna of Hawaii and that of the mainland until suitable studies are carried out on the North American Hoplothrips fauna.