Orseolia Kieffer & Massalongo in Indonesia

This is a genus of 28 known species mainly of tropical Asia, but three from tropical Africa, one from the Mediterranean Region and one from Japan and Korea. One of the more important species is O. oryzae, a pest of rice in Indonesia and elsewhere. All form leaf sheath galls on grasses ( Poaceae). One remarkable aspect of these galls is that they continue to lengthen after the larva turns into a pupa. DvLR & DvL (1926) attribute this to the continued absorption of water by the plant. Seven species are known from Indonesia and all were part of a generic revision by Gagné (1985) . They are fairly large gall midges with a wing length of 2.3-4.5 mm, the R 5 vein bowed to join C beyond the wing apex [Fig. 31h]. Heads lack an occipital protuberance. The last flagellomere usually has a conical extension at its apex [Figs. 27f, 31j]. Male flagellomeres have two nodes, the proximal spherical, with one whorl of looped circumfila, the distal prolonged, slightly constricted at midlength, with two whorls of looped circumfila. Tarsal claws are simple, narrow, bent at distal third, and are as long as the empodia [Fig. 31g]. Female cerci are large, ovate and covered with setae among which is a pair of thick, blunt, apical setae [Fig. 31e]. Some of the best taxonomic characters in the genus are differences in male terminalia and pupal antennal horns. Larvae are known for only two species but they do have a spatula. We do not repeat below all details of descriptions from Gagné (1985) but present additional, new morphological drawings as well as illustrations of galls from DvLR and DvL (1926).