Metrocoris squamifer Lundblad, 1933

Zettel, Herbert & Tran, A. D., 2009, First Inventory Of The Water Bugs (Heteroptera: Nepomorpha: Gerromorpha) Of Langkawi Island, Kedah, Malaysia, Raffles Bulletin of Zoology 57 (2), pp. 279-295 : 292-293

Metrocoris squamifer Lundblad, 1933

Material examined. – Datai environment: 1 male (apterous), HP1; Datai rain forest: 1 male, 1 female (apterous), 1 male (macropterous), HE1; Telaga Tujuh – Air Telaga: 1 male, 2 females (apterous), HZ1a. Temurun Waterfalls: 3 males (macropterous), 3 female (apterous), HZL2 . Gunung Raya: 1 male (macropterous), HZL4 a. Durian Perangin: 1 male, 1 female (apterous), L5HZ. Air Tejun: 1 male (apterous), HZL10 .

Remarks. – Identification of the species of the Metrocoris nigrofasciatus group is difficult. Identity of M. squamifer specimens from Langkawi has been confirmed by comparison with Malaysian specimens in NHMW identified by Dr. Ping- ping Chen. Using the key characters in Chen & Nieser (1993), male specimens might be identified as M. nigrofasciatus Distant, 1903 due to the fact that the subapical tooth on the fore femur is of variable shape and often reduced in small apterous and in all macropterous specimens. Distinction of these two species should be based on genitalia, especially on the shape of the paramere. The paramere of M. squamifer has a distinct ventral angle – although rarely so strongly pronounced as in the figure by Chen & Nieser (1993) – but the parameres of M. nigrofasciatus and M. nigrofascioides are evenly rounded. Although sorting males of M. squamifer and M. nigrofascioides is easy by the absence or presence of a notch on the fore femur, females can be distinguished only by colour, M. squamifer being on average lighter than M. nigrofascioides . The key character for females of M. squamifer given in Chen & Nieser (1993) is the colour pattern of tergite 8, but it could not conclusively separate the Langkawi specimens because apterous females from Langkawi have a black base of tergite 8. However, if tergite 8 is partly retracted into tergite 7, in some M. squamifer females a colour pattern appears which corresponds with the key character. Usually the yellow colour on tergite 8 is reduced to a small circular spot in M. nigrofascioides , but more extended in M. squamifer . For separation of females, authors used the extension of the mesopleural stripe (reaching further posteriad in M. nigrofascioides than in M. squamifer ), and the result agreed well with the identification of males from the same samples. Macropterous females are generally lighter than apterous females of the same species, and this morph of M. nigrofascioides was assigned to the males from the same sample.

Distribution. – Southern Thailand, West Malaysia, Sumatra, and Java (Chen & Nieser, 1993).