Orasema sixaolae Wheeler & Wheeler

Baker, Austin J. & Heraty, John M., 2020, The New World ant parasitoid genus Orasema (Hymenoptera: Eucharitidae), Zootaxa 4888 (1), pp. 1-84 : 48-50

Orasema sixaolae Wheeler & Wheeler

urn:lsid:zoobank.org:act:4CB6983B-FC4A-4DCD-90D5-D4974A1AE2C1

( Fig. 24 )

Orasema sixaolae Wheeler & Wheeler 1937: 163–164 .

Diagnosis. Distinguished from O. brachycephala by the flagellomeres being as wide as long (cup-shaped) with distinct peduncles ( Fig. 24D, E ) and the petiole much longer than the hind coxa. Distinguished from O. tinalandia by having more coarsely reticulate sculpture on the mesoscutal midlobe ( Fig. 24F ) and the petiole much longer than the hind coxa.

This species is most similar to O. nebula but can be recognized by the more coarsely reticulate sculpture on the face ( Fig. 24B ), a generally larger MSP:EYH that gives the head a more triangular, less circular appearance, and a longer/thinner petiole in both sexes.

Description. Female. Length 1.5–2.1 mm ( Fig. 24A ). Color. Head and mesosoma dark with iridescence. Mandible brown; Femora mostly brown, tips pale; tibiae yellow. Head ( Fig. 24B ). Head in frontal view subquadrate; HW:HH = 1.1–1.2; face completely reticulate to slightly costate on frons; longitudinal groove between eye and torulus present; eyes bare, IOD:EH = 1.5–1.8; MS:EH = 0.6–0.9; malar depression absent; supraclypeal area as long as broad, equal to length of clypeus, smooth; clypeus smooth to shallowly reticulate; epistomal sulcus vaguely defined. Labrum with 4 or 5 digits. Mandibular formula 3:2; palpal formula 3:2. Occiput with dorsal margin evenly rounded; temples absent. Pedicel globose, broader than F1. FL:HH = 1.1–1.3; anellus disc-shaped; F2L:F2W = 1.0–1.5, F2L:F3L = 1.0–1.2; following funiculars subequal in length, gradually broader; clava subovate ( Fig. 24D ). Mesosoma ( Fig. 24C, F ). ML:MH = 1.1–1.4. Mesoscutal midlobe reticulate, bare or with very minute setae; lateral lobe smooth. Axilla smooth; scutoscutellar sulcus broad, irregularly foveate, narrowly separated from transscutal articulation; mesoscutellar disc slightly longer than broad, reticulate; frenal line regularly foveate; axillular sulcus indicated by a weak longitudinal carina. Propodeal disc with median carina, smooth laterally ( Fig. 24G ); callus with several short setae on dorsal margin. Prepectus, mesepisternum, and propleuron reticulate. HCL:HCW = 1.7–2.3; HFL:HFW = 6.1–7.0, evenly covered with short, dense setae. FWL:FWW = 2.3–2.5, FWL:ML = 2.4–2.8; basal third of wing bare, including speculum and costal cell, wing disc densely setose; submarginal vein bare; stigmal vein perpendicular to anterior wing margin; postmarginal vein several times longer than stigmal vein. Hind wing costal cell with a broad bare area. Metasoma. PTL:PTW = 3.1–4.2, PTL:HCL = 1.1–1.4, areolate-reticulate, lateral margin rounded, ventral sulcus present with margins narrowly separated. Antecostal sulcus foveate; acrosternite posteriorly rounded; apical setae of hypopygium present, minute. Ovipositor with subapical carina present; first (ventral) valvula with 6–8 small, narrowly separated teeth, second (dorsal) valvula with 6 or 7 annuli that are broadly separated dorsally by smooth area.

Male. Length 1.5–2.0 mm. HH:HW = 1.2–1.3. FL:HH = 1.3–1.5; F2L:F2W = 1.2–1.4 ( Fig. 24E ). Tibiae yellow. PTL:PTW = 6.2–7.8, PTL:HCL = 1.7–2.5.

Planidium. Described by Wheeler and Wheeler (1937).

Pupa. Fits the general description for Oraseminae pupae provide by Heraty (1994), with three large tubercles along the dorsal margin of the petiole and the prominent transverse abdominal ridges being the most diagnostic features of the subfamily. This species has stronger tubercles coming from the abdominal ridges than the pupa of O. tolteca ( Fig. 19D ).

Hosts. Solenopsis tenuis Mayr in Costa Rica ( Wheeler & Wheeler 1937) and Solenopsis picea Emery in Mexico.

Both species of Solenopsis make their nests in dead twigs, where parasitized brood and Orasema pupae were found. In southern Mexico, dead twigs were placed as baits at coffee plantations to monitor Solenopsis activity, and O. sixaolae were found in many of these plantations (de la Mora Rodríguez et al., unpublished).

Plant associates. Unknown, but possibly coffee, Coffea arabica (L.) ( Rubiaceae ).

Distribution ( Fig. 21 ). Argentina: BA, MN, SA; Belize: TO; Brazil: SP, MG; Costa Rica: AL, GU, HE, LI, PU; Ecuador: NA, OR; Honduras: OL; Mexico: CS, VE; Peru: MD; Trinidad: SL; Venezuela: BO. Specimens collected throughout the year.

Material examined. Syntype. COSTA RICA. Limon: No. 375 Sixaola River , 9 ° 32’N, 82° 42’W, vii.1924, G.C. Wheeler [1♀, deposited in USNM: UCRCENT00248527] . Additional material examined. 62 specimens, see supplementary material.

Discussion. This species has the largest known distribution of any species in Oraseminae , even though it is far less morphologically diverse than O. coloradensis . Specimens of O. sixaolae have been collected at a fairly even rate throughout the year (49 records), indicating that tropical/subtropical species of Orasema are far less ephemeral than the temperate species found in the Nearctic. Despite their presence in previous collections, our sampling in Trinidad (2013) and Costa Rica (2016) failed to find any additional O. sixaolae .

Figures

FIGURE 19. Immature stages of Orasema tolteca. A, planidium head, ventral; B, planidium habitus (dorsal left and ventral right); C, planidium habitus, lateral. D, pupa habitus, dorsolateral. Modified from Heraty (1990).

FIGURE 21. Distribution map of species in the Orasema sixaolae species group.

FIGURE 24. Orasema sixaolae. Female (UCRCENT00282692): A, habitus, lateral; B, head, anterior; C, mesosoma, lateral; D, antenna; F, mesosoma, dorsal; G, propodeum, posterior. Male (UCRCENT00247779): E, antenna.