TAXONOMIC REVIEW OF AMITUS (HYMENOPTERA: PROCTOTRUPOIDEA, PLATYGASTRIDAE) OF THE WESTERN HEMISPHERE

Abstract Collections of Amitus (Hymenoptera: Proctotrupoidea, Platygastridae) from the Western Hemisphere are referred to the following species: from Canada and the United States, A. aleurodinis Haldeman, A. granulosus n. sp., and A. gibbosus n. sp.; from Mexico and South America, A. spiniferus (Brethes), A. pigeanus n. sp., A. hesperidum Silvestri, and A. fuscipennis n. sp. A lateral plate-like process on the male fourth antennal segment is regarded as a phenocline, characteristic of species or species groups.


DIAGNOSIS.
A . granulosus is readily identified from other species of Amitus by the short, oblique process on the male fourth antennal segment, a vertical keel originating between the antennal bases extending over halfway up the frons, and the very scaly mesonotum and scutellum.
DESCRIPTION. Female. Length, 1 mm. Head in top view very full, oval, twice as wide as long; occiput and vertex scaly, with no trace of a carina; lateral ocelli nearer to eyes than to median ocellus (2: 1); ocellar triangle densely reticulate; face reticulate above, appearing aciculate below; clypeus broad, the face with a keel originating between antennal bases, extending over halfway up the frons; entire head deflexed. Antenna1 segments I1 and I11 considerably longer than wide, IV to VII progressively shorter and broader, and VIII to X forming an enlarged club.
Mesonotum and scutellum flat, reticulate except on the apical half of the median lobe of the mesonotum and a median strip on scutellum which are smooth. Notauli complete, broad apically, each with a deep basal pit; scutellum transverse, gently sloping caudad, the dorsal surface separate from the posterior surface by an irregular ridge. Pronotum reticulate on humeral angles; pleura bare, polished, wrinkled under forewing and with a deep fovea extending across middle or mesopleura.
Abdomen as long and broad as thorax, depressed, nearly circular in top view, sometimes broader distally; tergite I very short, transverse, dilated laterally; tergite I1 with deep basal foveae and deep striae covering most of the surface. Remainder of gaster less than half as long as tergite 11, polished, sparsely setose.
Head and thorax black; gaster piceous to black; legs dark brown, antennae yellowish brown.
Males. Length, 0.93 to 0.98 mm. Similar to females except with less pronounced sculpture; antennae very long, slim, as long as the entire insect; lateral plate of antennal segment IV short, narrow, oblique. Pedicel short, subglobose; remaining segments long, pubescent, becoming gradually shorter distally. Wings extending well beyond tip of abdomen. Colored as in the female. Paratypes, 9 females, 5 males, same data as holotype, deposited in USNM, CNC.

DIAGNOSIS.
A. gibbosus was set apart because of its unusually short eye length, long malar line, and its overall convexity and depth of sculpture, which surpass the limits of variation in A. aleurodinis.
Thorax convex, with complete notauli; scutellum as high as mesonotum, both uniformly scaly; propodeum with a foamy membrane.
Wings extending well beyond apex of abdomen, transparent, with long fringes. Abdomen robust, varying from shorter than to as long as the thorax; tergite I carinate medially, foveate submedially, the foveae pubescent; tergite I smooth at the extreme sides. Tergite I1 transverse (25: 18), broadest distally, tergites 111 to VI progressively shorter, about half as long as I and I1 combined; tergite VI triangular.
Body dark reddish brown, the legs and antennae yellowish. Male. Length, 0.9 mm. Essentially like the female, except antennal segments beyond I11 subequal in length and width, 3.5 times as long as wide; pedicel and segment I11 equally long, each shorter than segment IX; antennal segments 111 to X uniformly clothed with subsequent pubescence. Abdomen shorter than thorax (25:30).

Mexico and South America
Species from Mexico and South America are referred to A. spiniferus (Brethes), A. pigeanus n. sp., A. fuscipennis n. sp., and A. hesperidum Silvestri, an introduced species. Three species groups are represented. A. pigeanus is sufficiently divergent from any other Amitus species to suggest a new subgenus. A. spiniferus and A. hesperidum share several characters and form a unit more closely allied to the northern A. aleurodinis, but possess a flared interantennal projection which is absent in A. aleurodinis. A. fuscipennis is differentiated by the infuscated wings and lack of an interantennal projection.

Figs. 5-7
DIAGNOSIS. Ocelli near the eyes than median ocellus; flagellar segments very short in both sexes, the female club proportionately very large; face with a flared process between the antennal bases; male antennal segment IV with a short, broadly oval plate; female genitalia spine-like, more obvious than in other species except A. hesperidum; thorax and abdomen without unusual features, the wings very narrow, transparent.
MATERIAL EXAMINED (in CNC, USNM). Callao, Peru, ex aleyrodid, 1956, and Mazatlan, Sinaloa, 10 July 69, P. DeBach; 6 specimens. Amitus pigeanus n. sp. DIAGNOSIS. A. pigeanus diverges markedly from all other Amitus species. The lateral plate on the male fourth antennal segment covers the whole outer side of the segment, and is bordered by short setae. The scutellum is oval, rounded in side view as in Platygaster. The propodeum has a reduced membrane and two widely separated carinae either side of the midline. The species could be placed in a new subgenus,~but-it is probably more suitable to broaden the concept of Amitus instead, since the genus has traditionally been based on a limited amount of material and was unavoidably restrictive. DESCRIPTION. Female. Length, 1 mm. Head in top view as wide as thorax, nearly half as long as wide; occiput and vertex lightly reticulate (appearing microgranular with a light microscope); postocellar line twice as long as ocellocular line; face faintly reticulate; antennal scape surpassing vertex, pedicel twice as long as wide; antennal segment I11 as long as pedicel, narrower, the remaining flagellars progressively shorter until segment VII, which is quadrate; club not sharply differentiated, about half as long as the flagellum, gradually widened toward distal third.
Thorax as long as broad, with moderately angulate humeri; mesonotum wholly reticulate, with complete notauli; scutellum half as wide as mesonotum at humeri, oval, smoother than mesonotum, margined as in Platygaster. Propodeum visible at the sides beneath the scutellum, carinate as in Platygastrinae but with the carinae widely separated.

1750X.
Gaster as long as thorax, slightly longer than broad (probably variable in this respect); tergite I with 2 submedian, pubescent pits, the median area raised, carinulate; lateral areas flatter with sparse, long setae at the sides; tergite I1 deeply foveate either side of the median plate, with a short fan of striae radiating from each fovea; tergites 111 to VI subequal, their combined length about a third that of tergite 11. Gaster broadest behind the middle.
Forewing 1.2 times as long as the thorax and abdomen combined, with the fringe very short, at most 0.05 as long as the maximum width of the wing.
Body piceous, legs reddish brown to dark brown; antennae yellowish. Males. Generally like the female but without an antennal club; flagellars short, less than twice as long as wide except segment IV, which is 2.5 times as long as wide, and segment X, which is twice as long as wide. Segment IV with a large, plate-like process covering entire outer side of the segment.
Legs and antennae honey yellow, a variable condition; body color variable from light reddish brown to black.

DIAGNOSIS.
A. hesperidum differs from A. aleurodinis, which it closely resembles, by having a flared process between the antennal bases. It differs from A. spiniferus by having the lateral ocelli nearer to the median ocellus than to the eyes, a longer plate-like process on the male fourth antennal segment, and longer flagellars in both sexes. The thorax, gaster, and fourth antennal segment differ insignificantly from those of A. fuscipennis (Figs. 8 to 10) but the wings are transparent, not fuscous as in that species. DESCRIPTION. Female. Length 0.8 mm. Head in top view more than twice as wide as long (39:16); lateral ocelli nearer to median ocellus than to eyes (4:s); occiput deeply scaly, vertex more lightly so; vertex in front view forming a broad, low arc, with raised protuberances at the ocelli; eye height greater than length of malar line (16:9); face reticulate above, aciculate below and on the sides; interantennal space with a flared process; clypeus protrusive, sharply angled at the sides, as broad as interantennal space. Pedicel twice as long as wide, a little longer than antennal segment 111; segments I11 and IV subequal, about twice as long as wide; segments V, VI, and VII progressively shorter and broader; club as narrow basally as segment VII, broadening a little distally, two-thirds as long as flagellum.
Thorax only moderately flattened, the scutellum somewhat drawn out at the apex, not evenly rounded; scutellum smooth or faintly reticulate laterally, the median area smooth to the apex. Pleura typical, without diagnostic features.
Gaster somewhat longer than thorax, tergite I with a median, carinate elevation, with submedian pits and irregular carinulae at the sides; tergite I1 striate on the basal half; tergites I11 to VI each with long setae either side of a bare median area. Genitalia as in A. spiniferus.
Body piceous, legs and antennae yellow. DESCRIPTION. Female. Length, 0.9 mm. Head in top view 1.7 times as wide as long; narrowed toward the vertex, both the vertex and occiput lightly reticulate; lateral ocelli much nearer to median ocellus than to eyes (49); frons broad, lightly reticulate, diagonally aciculate FIGS. 8-1 1. Amitusfuscipennis. 8, head, thorax, 2 0 0~; 9, 0 , 1 0 0~; 10, 0 gaster, 200X; 11, 6 antennal segment IV, 1000x. below the middle; space between antenna1 bases smooth, without a flared process; vertex in front view forming a low arc, without ocellar protuberances. Pedicel 2.5 times as long as wide, very little longer and narrower than segment IV; segments V to VII gradually shorter, each about equally wide, segment VII about three-fourths as wide as long, not quadrate; club 0.33 as long as funicle, not especially widened. Antenna1 pubescence nearly spinose, especially near the ends of the segments.
Tergite I carinulate in the center, with sublateral pits filled with pubescence, the extreme lateral areas smooth; hind margin of tergite I with rather long setae projecting over the forward margin of tergite 11. Tergites I1 to VI without unusual features, the entire gaster somewhat longer than the thorax. Body piceous; legs and antennae dark reddish brown, without yellow markings; wings fuscous.
Male. Coated for scanning electron microscopy, not described.