Megalothrips Uzel

Megalothrips Uzel, 1894: 224–5. Type-species: Megalothrips bonannii Uzel, by subsequent designation, Bagnall, 1909: 350.

The genus Megalothrips Uzel was originally established with M. bonannii as the type-species from Czechoslovakia. The generic definition of Megalothrips was discussed in Mound and Palmer (1983), and redescribed in detail in Okajima (2006) and is not repeated here. The important features of the genus are the head long and strongly elevated dorsally, the compound eyes relatively small, the maxillary stylets very long which are retracted to eyes and close together medially, the pronotum short and broad, and the lateral wings of pelta slender. It may be closely related to Bacillothrips Buffa from Europe, Egchocephalothrips Bagnall from New Caledonia and Megathrips Targioni-Tozzetti from Europe and North America. From Bacillothrips and Megathrips, Megalothrips can be distinguished by the features indicated above. However, from Egchocephalothrips, it cannot be distinguished satisfactorily, and there is a possibility that this genus may eventually be treated as a synonym of Megalothrips (Mound & Palmer 1983). The genus Bactrothrips, at least the species from Africa and Asia, are probably more distantly related to this genus rather than Bacillothrips and Megathrips. Unlike Megalothrips, they have the compound eyes well-developed and bulged, and the antennae elongate, of which the intermediate segments have the pedicels very long and slender with club-head-like apices.

There are nine species included in the genus Megalothrips, of which two species are known from Europe, three species from North America and four species from Asia including M. sulawesicus sp. nov. described below from Sulawesi, Indonesia. Despite these three areas being somewhat isolated from each other, there seems to be no significant morphological differences between species from different areas.

Two patterns of the notopleural sutures in Megalothrips species from Asia

The incomplete notopleural suture of the genus Megalothrips may be important for the discrimination of species, because the condition of this suture appears to be variable within the genus. The pronotal notopleural suture (= epimeral suture) is usually used as an important features for the determination of genus (sometimes species) level in both subfamilies of the family Phlaeothripidae. The condition of this suture, whether it is complete or incomplete, seems to be important.In the subtribe Idolothripina, most genera including Megalothrips have incomplete notopleural sutures. However, it should be noted that the expression ‘incomplete’ includes various states. If this suture does not reach the posterior margin of pronotum slightly, it is incomplete, and if it is only halfway or is almost vestigial, it is also incomplete. In this study, two different conditions of the notopleural suture in Megalothrips species in Asia have been observed. This suture separates the pleural region, that consists of the episternum and epimeron, and pronotum. More precisely, it is a continuous suture of the noto-epimeral suture that separates epimeron and pronotum and the noto-episternal suture that separates episternum and pronotum. One is found in M. rotundus from China and M. sulawesicus sp. nov. described below from Sulawesi, Indonesia: the noto-epimeral suture is largely reduced or vestigial, but noto-episternal suture is complete (cf. Fig. 97). The other is found in M. andrei from Peninsular Malaysia and M. curvidens from Japan: the noto-epimeral suture is completely lost, and the noto-episternal suture is vestigial or almost lost (cf. Fig. 102). Moreover, one poorly defined genus, Egchocephalothrips Bagnall, which may be closely related to Megalothrips, has complete notopleural sutures. According to Mound and Palmer (1983), however, the complete notopleural sutures of it could be an artefact due to coverslip pressure.

Key to Asian species of Megalothrips

(*: based on original descriptions and figures)

1. Pronotal notopleural suture vestigial, noto-epimeral suture absent, noto-episternal suture shortly present at lateral margin of pronotum or almost absent (cf. Fig. 102)................................................................... 2

-. Pronotal notopleural suture incomplete, noto-epimeral suture reduced to halfway (cf. Fig. 97), vestigial or almost absent, but noto-episternal suture complete or nearly complete........................................................... 3

2. Postocular setae pair I longer than 60µm in female, longer than 80µm in male; postocular pair II longer than interocellars, much longer than 100µm in female; tube 1.15–1.20 times as long as head in female, about 0.8 times in male............. andrei *

-. Postocular setae pair I shorter than 40µm in female, shorter than 50µm in male; postocular pair II much shorter than interocellars, usually shorter than 60µm in female; tube shorter than 1.1 times as long as head in female, shorter than 0.8 times in male................................................................................................ curvidens

3. Antennal segment III with basal 2/3 yellowish brown; interocellar setae longer than 1/2 length of postoculars pair II.................................................................................................... rotundus *

-. Antennal segment III dark brown, with extreme base yellowish (Fig. 95); interocellar setae much shorter than 1/2 length of postoculars pair II..................................................................... sulawesicus sp. nov.