OCR Text |
Show 154 ME. E. E. AUSTEN ON NEW DIPTEEOUS INSECTS, [Jan. 17, posterior fifth ; third segment with a similar brown transverse posterior band, which, however, is concave anteriorly for about a fourth of the width of the segment on each side of the median line; in the median line it is produced into a small angle, from which a faint brown median stripe extends forwards to within about one-seventh of the length of the segment from the anterior margin; fourth segment with, the extreme hind margin and three triangles brown ; two of the triangles are lateral in position, one in each posterior angle, and extend forwards and inwards to about the middle of the segment; the third is median, and narrower than the other two, and is prolonged as a median stripe to the anterior margin, before reaching which, however, it becomes faint; the markings on the fifth segment are similar to those on the fourth, but narrower, and the lateral triangles are so prolonged that they are only narrowly separated from the anterior margin; the median triangle, too, is here represented by a stripe, which, while expanding slightly posteriorly, is only about half the width of the median stripe on the preceding segment, and (in the typical specimen at least) is separated by about one-eighth of the length of the segment from the anterior margin; on the short sixth segment the lateral triangles (here almost reduced to stripes) reach the anterior margin without becoming indistinct, while the median triangle is represented by a small, but sharply defined, triangular spot, with its base in the centre of the anterior margin and its apex in the middle of the segment. The third longitudinal vein of the wings is nearly straight, and only slightly concave posteriorly; distal half of subcostal cell dark ochraceous ; knobs of halteres ferruginous. Brazil, region of the Amazons (Bates): one specimen. In the markings of the abdomen this species somewhat resembles B. gilva, but is at once distinguished by the colour of the dorsum of the thorax, as well as by the deeper colour of the scutellum and abdomen, and by its larger size. BACCHA GILVA, sp. n. (Plate V. fig. 7, d •) d • Length 9| m m. Pale yellow: thorax metallic brown in centre of dorsum, abdomen with brown transverse bands and other markings ; the abdomen is flat, broad,, not contracted at the base, but expanding regularly to the margin of the fourth segment. Wings with a yellowish tinge, especially towards the base ; veins yellow, the auxiliary and first longitudinal veins orange: alulas rudimentary. Face aud cheeks pale yellow, shining, the low facial tubercle dull. the face receding. Front yellow, with a black dot on the anterior face of the antenniferous projection ; the front clothed with brown pile, the upper part of the face below the antennae also with darkish pile ; vertical triangle elongated, though not very narrow, cinereous pollinose, the ocelli remote from the vertex; occiput fringed at the sides with golden yellow hairs. Antennce orange, third joint rounded ; arista brown, yellow at the base. Thorax |