Length, 16.5–20 mm.; diameters of the 2nd abdominal segment: dextro-sinistral, 6–6.5 mm.; dorso-ventral, 5 mm. Form robust, mod-erately flattened dorso-ventrally, oval in cross section. Body thickest in region of first three abdominal segments; thoracic and posterior abdominal segments of about equal depth and breadth; anterior and posterior extremities blunt.
Colour (alcoholic specimens), a dull cinnamon-buff, somewhat darker on dorsum of thorax. Integument opaque, leathery, tough; bearing an even, moderately dense, growth of minute hairs nearly concolourous with integument. Setae small, weak, inconspicuous; when broken the setigerous punctures hardly evident. The abdominal somites are divided into anterior and posterior annuli, the former with several transverse wrinkles across dorsum, the latter somewhat the longer and more smooth. Abdominal segments 7 and 8 with a caudo-
laterally directed, fleshy tubercle at each caudo-lateral margin. (Those of segment 8 shown in fig. 6). Segments 5 and 6 have very minute tubercles in the same positions.
Spiracular disk dorso-caudal. When expanded (fig. 7) occupy dorsal half of caudal aspect; when contracted (fig. 6) visible only as a transverse dorsal slit at about two-thirds the length of 9th abdominal segment. Of the six lobes borne by disk, the ventral pair are very large and fleshy, almost fused in median line; their apical margins with brown, chitinized lines. When disk is expanded the faces of ventral lobes are at right angles to vertical face of disk proper and form a horizontal shelf whose area is equal to that of disk. In contracted condition the faces of ventral lobes are turned upward to a nearly vertical position, concealing spiracles and face of disk, and in this position the fleshy caudo-ventral faces of ventral lobes form a tumid caudal end to the larva. From the middle of the caudo-ventral face of each lobe is borne a small, cylindrical, fleshy papillus. The disk proper is sub-quadrangular, the long dimension of quadrangle, dex-tro-sinistral. The nearly circular spiracles are dark brown, their centres a dead black; they are separated by about once and a half times diameter of one spiracle. The slender, conical, dorso-lateral lobes project dorsad from dorso-lateral angles of disk and at about mid-length turn abruptly laterad; the caudal face of their bases has a chitinized, faint brown line. The paired dorso-median lobes are very small, rounded, chitinized projections to either side of dorso-median line. From cephalic surface of each arises a small, fleshy, conical papillus that projects dorsad well beyond lobe itself. Save for the spiracles and chitinized areas noted, disk is concolourous with rest of abdomen.
The anal gills have the form of a broad circum-anal ring that is radially wrinkled, and are opaque white save for a dark brown, chitinized outer portion. When gills are retracted only this chitinized outer portion is visible. Apparently the gills serve as an organ of locomotion.
Head capsule (fig. 1), broad, massive, compact, heavily chitinized. Length, 3.5 mm.; breadth, 2 mm.; greatest depth (mid-length of lateral plates), 1.3 mm. Prefrons a long narrow triangle, its slightly concave base forming anterior margin, posterior apex slender, elongate; anterior two-thirds heavily chitinized, dark brown. Lateral plates mussel-valve-like in shape; anterior three-quarters and entire margin heavily chitinized, dark brown; the centre of posterior quarters membranous, yellowish brown, ventro-mesal anterior margins projecting to form the bars of mentum, toward lateral angles of dorsal cephalic margins with a single stout, long seta. Clypeus shallow crescentic, chitinized, dark brown; cephalo-lateral horns with a single, erect, brownish yellow seta. Labrum epi-pharynx rectangular, almost square; a transverse groove caudad of its cephalic margin; back of this groove the surface is slightly depressed, saucer-like, conspicuous whitish yellow; anterior to groove with cephalo-lateral margins chitinized, dark brown, bearing numerous long, stiff hairs and a pale slender papillus-like rod, the median cephalic portion emarginate. Antennae with first joint stout, cylindrical, dark brown except for yellow apex; 2nd joint minute, elongate oval, yellowish white. Man-
1. Head capsule of larva, Macromastrix albistigma Edw.
2. Mandible of larva, M. albistigma Edw.
3. Hypopharynx of larva, M. albistigma Edw.
4. Mentum of larva, M. albistigma Edw.
5. Maxilla of larva, M. albistigma Edw.
6. Ninth abdominal segment and contracted spiracular disk of larva, from above, M. albistigma Edw.
7. Expanded spiracular disk of larva, caudal aspect, M. albistigma Edw.
8. Pronotal breathing horn of pupa, M. albistigma Edw.
9. Pupa of M. albistigma Edw., ventral view.
dibles (fig. 2) stout, heavily chitinized; three blunt, cylindrical, apical, teeth, median tooth the largest and curved slightly mesad; a minute elevation at the base of dorsal tooth; dorsal margin near base of mandible, rounded, protruding, the crest of this protuberance minutely crenate; remainder of mandible smooth, the edges rounded; a pair of long setae borne from a common pit on proximo-lateral angle of ventral face. Prosthecal appendage a long, hairy papillus with a tuft of longer, yellow hairs at its apex. Maxillae (fig. 5) smaller than mandibles, flattened, sclerites distinct. Cardo large, sub-quadrangular, a pair of long, erect hairs borne from a common depression near middle of its anterior ventral face. Stipes a short, thick cylinder, slightly dilated distally, its proximal margin very oblique; apically it bears a prominent, conical palpal joint and, just before apex, a long stout seta that curves toward tip of palpus. Outer lobe short and stout with a pair of setae from a common pit at base of ventral surface; the rounded apex with a dense growth of yellow hairs and, on inner surface, a small chitinized cone. Inner lobe smaller, flattened triangular, and bears a small tuft of hairs directed meso-cephalad. Mentum (fig. 4) broad, prominent, barely constricted back of bases of lateral teeth; median tooth long, projecting; to either side three lateral teeth, smaller and flatter than median tooth; caudal cleft extends cephalad to a point opposite bases of second lateral teeth. Hypopharyngeal plate (fig. 3) narrow, anteriorly with a triangular median tooth and a pair of broad, incompletely double lateral teeth.