The Philippine journal of science. [Vol. 57, no. 1]

57, 4

Tokunaga: Chironomidx, IV

499

epicranial arm. Thus the vertex on this region appears to be
of a dark color due to the thick chitinization of the antennaria,
and the external distal region of the antennaria is shown as a
tubercle between the clypealia and precoila in the dorsal aspect.
The antenna (Plate 2, fig. 7) is articulated to the cephalic end
of the antennaria by means of the intermediation of the large
socketlike antacoria. The antenna is very small for the
size of the head capsule and 4-segmented. The proximal
segment is comparatively large, not cylindrical but somewhat
barrel-shaped, its length about twice its width or the length of
the remaining three segments taken together, provided with a
sensory pore on the dorsoproximal region, and membranous on
its distal end. In some cases it appears that there is a very
delicate hyaline seta on the base of this segment, but this is not
determined yet to be constantly present. The second antennal
segment is cylindrical and twice as long as wide. On the distal
membrane of the proximal segment, in a parallel position with
the second segment, there is a membranous trichoid sensilla,
Lauterborn's organ, which is as long as the distal three segments taken together and biramous on its distal region as in
T. torrenticola. The distal two segments are very minute and
brown. Besides these segments, on the distal membrane of
the second segment there are a chitinized sensory peg and two
tricoid hyaline sensille, which are all as long as the distal two
segments taken together. The segments of the antenna are
often incorrectly counted as three owing to the extremely delicate structures of the distal region of the antenna and to the
presence of the comparatively large sensory peg, which is brown
and as long as the two distal segments of the antenna proper
taken together.
THE MOUTH PARTS
The mouth opening is large and provided with a well-developed labrum, epipharynx, mandibles, mentum, and hypopharynx.
The maxillae are small, and the labial appendages are all atrophied.
The clypeolabrum (Plate 2, figs. 7, 8, and 10) is somewhat
trapezoid and composed of the thickly chitinized marginal structures and two chitinized plates, pre- and postclypeus, on the
membrane. The region of the postclypeus is demarcated from
the front by the straight frontoclypeal suture and from the
preclypeus by the shallow fold of the membrane and consists