Elachista argentosa Braun 1920

Elachista argentosa Braun (Figs. 27, 49, 94, 94a, 137.)
1920. Elachista argentosa Braun, Ohio Journ. Sci., xx, 168. Type 8 , Clermont County, Ohio [A. F. B. Coll.].
1923. Aphclosctia argentosa Forbes, Mem. 68, Cornell Univ. Agric. Exp. Sta., p. 221.
Face and head silvery gray, with a bluish metallic luster ; palpi silvery gray inwardly, fuscous beneath and outwardly ; antennae deep blackish brown throughout, slightly thickened in male. Thorax deep golden brown, shading to metallic gray and silver behind. Fore wings almost black with faint golden brown reflections in some lights; markings metallic silvery, with golden and bluish reflections; base of wing silvery; a fascia just before middle produced a little toward tornus on dorsum; opposite costal and dorsal streaks at twothirds, the costal curving outwardly in the middle of the wing and sometimes slightly dilated at its tip before apex, and rarely met by the dorsal streak. Cilia dark brown, apical scales forming a contrasting line. Hind wings broader in male, grayish brown, becoming bluish along costa near base. Legs silvery gray, middle tibiae and all the tarsi dark brown, and brown shading on the hind tibiae ; tips of segments silvery. Abdomen shining fuscous above, silvery beneath.
Alar expanse : 7 to 8 mm.
Male genitalia (figs. 94, 94a) : uncus lobes small, not separated at base, a few short setae near their outer margins; gnathos ellipsoidal; free outgrowth of harpe reduced, basal process of sacculus short, club-shaped, with long setae ; posterior margin of anellus strongly sclerotized, each lobe prolonged into a finger-like process; vinculum broad, with a short anterior projection; aedeagus (fig. 94a) with an elongate dorsal, and a shorter ventral basal enlargement, apex dorsally produced into a long curved acutely pointed process ; manica present ; no cornutus.
Female genitalia (fig. 137) : genital plate specialized, its median anterior margin strongly sclerotized and indenting the seventh segment ; ostium opening in a broadly oval membranous area in the genital plate ; the lateral lines from ostium nearly straight, but little divergent ; dorsal posterior margin of eighth segment bearing about ten strong setae ; bursa copulatrix large, bilobed, spiculate, signum an elongate dentate band ; ductus bursae gradually narrowing to the small ostium, and sclerotized just before ostium; inception of ductus seminalis just anterior to this sclerotized ring.
Specimens examined: 12 8 , 8 9 .
Ohio: Clermont County, 8 type, under rearing record B.1008, imago June 1, 1919; 2 8 paratypes under B.1008. imagoes June 2 and June 3, 1919; 3 9, under B.1083, imagoes June 1, June 7, 1922; Cincinnati, 8 8,4 2. under rearing records B.1008, B.1034, B.1041, with dates of emergence from May 24 to June 13, 1920 and 1922; 1 8 , 1 2 , captured on the wing, June 7, 1906, and June 23, 1904 [A. F. B. Coll.]. The larvae mine leaves of speeies of Carex, most commonly the narrow-leaved species, during April and early May. The mine ( fig. 27) extends from the tip of the leaf downward and lies nearer the upper side; the parenchyma is partially consumed and the mine appears greenish except near the point of exit over the midrib where the parenchyma is consumed and the epidermis wrinkled, forming a tunnel opening by a transverse slit to the outside; the larva may mine beyond this point, returning to the tunnel. When a new mine is made, as sometimes occurs, a little silk is spun over the entrance and the same tunnelshaped exit constructed before feeding is resumed. The larva is pale yellowish white, with head and thoracic shield pale brown ; a darker spot on each of the fourth and fifth abdominal segments.
The pupa (fig. 49) is enclosed in a very open irregular meshwork. The dorsal abdominal surface is less flattened than in the two preceding species, the spiracles but little produced ; the head and thorax are more elaborately tuberculate than in the other species of the section ; the dorsum of the mesothorax bears four rows of bead-like tubercles ; there are lines of fine tubercles on the wings.
In venation the fore wing of E. aryentosa differs from that of madarclla in that Cu lb arises opposite the origin of R 2 , but R 2 and R 3 are farther apart than are R^ and R 2 , as in madarclla. The dilated tip of the costal streak corresponds in position to the pale golden or silvery spot in the middle of the wing before apex in E. madarclla and E. cnitcsccns.
6. COSMIOTES Clemens Cosmiotcs Clemens, 1860. Proc. Acad. Nat. Sci. Phila., p. 8. Genotype. — Cosmiotcs illectella Clemens, i860.
Head smooth-scaled; labial palpi long, diverging and somewhat recurved, third segment much shorter than the second, acute; antennal pecten consisting of a few fine hairs near base of scape.
Fore wing (figs. 16, 16a, 16b) lanceolate, acute; R 4 , Rand M, stalked together, R 4 out of the stalk before the forking of R, + M. v sometimes the three veins separating close together; M., absent, M 3 and Cu la united; 1A + 2A without basal forking (lb simple).
Hind wing (fig. 16) one-half the width of the fore wing; acute; M, stalked with R s , M 2 and M, absent; cell open between Cu Vi and R a + M r
Hind tibiae with long hairs above, shorter hairs below; middle spurs before the middle of the segment.
Male genitalia (figs. 56, 56a, 57, 57a) ; lobes of the uncus widely separated, c'aw-like, apices directed inwardly, setose on the inner surfaces; socii, two small drooping papillae; gnathos, a small spined knob; harpe very long, produced into an acute spine at apex ; without free arm ; sacculus process long, slender, apex -somewhat enlarged, concave and setose inwardly ; ventral plate of anellus with two broadly diverging arms at base, deeply cleft at apex into two blunt conical setose lobes ; anellus anteriorly produced into a large membranous pouch ; vinculum abruptly narrowing into a long point ; aedeagus long, slender, evenly tapering, curving near apex, a keel-shaped projection at base; no cornutus.
Female genitalia (figs. 103, 103a, 104, 105); seventh abdominal sternite strongly sclerotized and modified, its posterior margin with a deep median sinus, on each side of which it is produced as a thickened lobe; the margins of the sinus form the ventral anterior and lateral borders of the ostium; ductus bursae short, sclerotized through the seventh segment; inception of the ductus seminalis at the posterior end of the finely spiculate bursa copulatrix ; signum a circular sclerotized patch, from which projects a pair of opposite heavy spines, with one or more smaller accessory spines.
The species of Cosmiotcs are miners in leaves of many species of grass, and are not specific as to food plant.
The eggs, larvae and mines are very similar to those of the typical species of Elachista of Section II. The pupa agrees with that of Elachista in general structure, in the tubercles of head and mesothorax, and with the more specialized species in the produced spiracles, but may be distinguished from all pupae of that genus by the pair of backwardly directed spines on the vertex (fig. 50).
In describing Cosmiotes, Clemens wrote: "the subcostal nervure . . . sends from the angle of the disk a trifid branch, which is either forked on the costa by an exceedingly short branch before the tip, and gives rise at about its middle to a branch to the inner margin, or is trifid at its extreme tip. The median is twoor three-branched near its end." Of the hind wing he wrote: "The median is well indicated, with tzvo or three short approximated branches about the middle of the inner margin."
As the type of illectella, the first of the three species described at that time, is not in existence, it is necessary to deduce its structure from Clemens' statements. In the fore wing, the alternative, median twobranched, is applicable to illectella alone, as in both of the other species described at the same time (of which the types are in existence), M 2 , M 3 + Cu la and Cu lb of the fore wing are all present (i.e., median vein three-branched) . Illectella is thus characterized : "Median vein of hindwings two-branched. Apical vein trifid at tip," that is, M 3 of hind wing absent, and R 4 , R-, and M, of the fore wing separating close together from the common stalk (cf. fig. 16b, 2 ).
The unique and characteristic genitalia, together with the different venation, warrant the removal of Cosmiotes from synonymy with Elachista, and its restriction to the species posessing those characters. In addition to the three American species, the European stabilella Frey and nigrella Haworth belong here. They form a closely related group of species of similar aspect, distinguished from one another by slight differences, best by characters of the female genitalia.

Elachista argentosa is a moth of the family Elachistidae. It is found in the United States, where it has been recorded from Ohio and Maine.

The wingspan is 7–8 mm. The forewings are almost black with faint golden brown reflections. The markings are metallic silvery, with golden and bluish reflections. The base of the wing is silvery. The hind wings are grayish brown, becoming bluish along the costa near the base. Adults have been recorded on wing from May to August.

The larvae feed on Carex species. They mine the leaves of their host plant. The mine extends downward from the tip of the leaf. Larvae may leave their mine and start a new one. Some silk is spun over the entrance of the old mine. The larvae have a pale yellowish white body and a pale brown head. Mining larvae can be found in April and early May.