1. Spiracular disk with the dark markings less extensive; the mark of the lateral lobes not contiguous with the spiracle or the triangular area on the disk; dorsal marking indistinct or lacking.D. winnemana Alex.
Spiracular disk with the dark markings more extensive; the mark of the lateral lobes suffusing the ventral inner margin of the spiracle and usually closely approximated or nearly contiguous with the triangular area on the disk; dorsal marking black, transversely rectangular.D. minima Alex.
Description of the Species.
DESCRIPTION OF THE SPECIES
1916 Dicranoptycha winnemana Alexander; Proc. Acad. Nat. Sci. Phila., pp. 500, 501; Pl. 25, fig. 12.
Larva.—Length, 20-22 mm.
Diameter, 0.9-1.1 mm.
Coloration varying from white to almost black depending on the nature and amount of the food eaten which shows clearly through the transparent integument. The fat-bodies likewise show through and give a white color to the larva especially after death.
Form very elongate ([fig. 1]), body terete; integument very glabrous, transparent and glassy. Prothoracic segment a little longer than the mesothorax which, in turn, slightly exceeds the metathorax. The intermediate abdominal segments are elongated. The basal ring of sternites two to eight bears a transverse band or area of microscopic chitinized spicules, the one on the eighth segment split lengthwise by a capillary line. A similar band occurs in the same position on the dorsum of the eighth segment but the pleural region is devoid of such a band.
Spiracular disk ([fig. 8]) moderate in size, obliquely truncated, surrounded by four lobes, a pair of small, slender, lateral lobes and short, broader ventral lobes. The usual dorso-median lobe is lacking but its position is indicated by a gently rounded convexity. The inner face of the lateral lobe bears a narrow semi-lunate black mark with the concavity toward the spiracle, the proximal end acutely pointed. The ventral lobes bear a similar but smaller subrectangular black mark. A pale and usually indistinct dusky mark occupies the inner face of the dorsal lobe. On the disk between, and slightly below the level of, the spiracles is a large brown triangular or V-shaped mark. The spiracles are small, separated from one another by a distance equal to about 2.5 to 3 times the diameter of one; the center-piece of the spiracle is black, the ring yellow surrounded by an outer dusky margin. Anal gills fleshy and protuberant as a blunt ring surrounding the anus ([fig. 10]).
Head-capsule ([fig. 2]) of the compact, massive type of the Limnobiini; præfrontal sclerite ([fig. 3]) large and distinct; the sclerite broad with the sides subparallel to about midlength, thence tapering gradually to the tip which is entire; there are two or three punctures at the margin before midlength. Interno-lateral plates narrow, a little longer than the præfrons; externo-lateral plates very broad, thin and flattened with the posterior margin very obtuse and the inner ventral portions continuous with the mental plate. Labrum ([fig. 3]) very broad and extensive, flattened, pale in color, the anterior margin with about two sense-organs. Mentum ([fig. 4]) deeply split behind but not completely divided, the anterior margin with three primary teeth that are subequal in size or the middle one a little smaller; a much reduced lateral tooth on either side. Præmentum smaller than the hypopharynx, in outline roughly oval or semicircular with the two labial palpi surrounded by hairs at the base. Hypopharynx ([fig. 5]) consisting of two chitinized arms that are contiguous but not fused medially, the concavity between them filled with a rounded cushion that is covered with tubercles arranged in more or less distinct oblique parallel rows. Antennæ ([fig. 6]) two-segmented, the basal segment cylindrical with an auditory plate on the face at beyond midlength; apical segment long and slender, in length but slightly less than the basal segment, tapering gradually to the bluntly rounded apex. Mandibles ([fig. 7]) simple with the teeth blunt; apical point longer than the lateral teeth; dorsal tooth single, broad, very flattened and obtusely pointed; ventral teeth two, a little smaller than the dorsal tooth. Maxillæ ([fig. 2]) of a generalized structure, the cardines distinct and feebly chitinized; distal lobes of the organ consisting of a subequal inner and outer lobe; the outer lobe with an abundance of long, delicate hairs and bearing a few sensory papillæ including one larger palpiform organ.