A new species, Encarsiella tamaulipeca Myartseva and Coronado-Blanco sp. nov., from Mexico is described and illustrated. A new combination is proposed, Encarsiella narroi (Gomez & García) from Encarsia. A key to the species of Encarsiella (females) of the New World is given.
Among the parasitic Hymenoptera, species of the family Aphelinidae (Chalcidoidea) are among the most important biological control agents of insect pests. Aphelinid species play a significant role in ecosystems as natural enemies of many homopteran hosts and have been used successfully as biological control agents in Mexico and in many parts of the world (Clausen 1978).
The genus Encarsiella Hayat (1983) belongs to the subfamily Coccophaginae sensuDe Santis (1948) and Hayat (1985), tribe Pteroptricini Ashmead, that also includes the genera Encarsia Foerster, Dirphys Howard, Bardylis Howard, Coccophagoides Girault and Pteroptrix Westwood (Hayat 1998). Relationships within the family Aphelinidae have been studied by many taxonomists, but the classification of the aphelinid genera into subfamilies and tribes is still in formative stages (Hayat 1994, Yasnosh 1976, Shafee & Rizvi 1991 and Hayat 1998).
Encarsiella is characterized by having an 8-segmented antenna in both sexes, the third segment of the club oblique or transverse at apex, linea calva absent, stigmal vein narrow, submarginal vein with 2-4 long setae, mesoscutum with a variable number of setae but always more than 6 and the axilla elongate and strongly projecting forward.
Encarsiella is closely to the genera Dirphys and Encarsia. The differences among these genera are shown in the following key:
1.Axillae small and separated medially by more than the maximal length of an axilla. Mid lobe of mesoscutum with reduced number of setae arranged in bilateral symmetry. Scutellum distinctly wider than long
—Axillae large and separated medially by less than the maximal length of an axilla. Mid lobe of mesoscutum with many scattered setae, not arranged in bilateral symmetry
2.Side lobes divided; sculpture of mesoscutum aciculate. Scutellar placoid sensilla closely placed, separated by about diameter of a sensillum
—Side lobes not divided; sculpture of mesoscutum imbricate-reticulate. Scutellar placoid sensilla widely placed, separated by distance distinctly longer than diameter of a sensillum
Most Encarsiella species are solitary endoparasitoids of whiteflies belonging to the subfamily Aleurodicinae (Homoptera, Aleyrodidae). However, Encarsiella boswelli (Girault) is known to attack eggs of Heteroptera (Polaszek & Hayat 1990), and an undescribed species from India was reared from nymphs of Psyllidae (Huang & Polaszek 1996).
Nine species of Encarsiella are known worldwide; of these, four are recorded in the New World: E. aleurodici (Girault), E. magniclava (Girault), E. pithecura Polaszek, and E. noyesi Hayat (Huang and Polaszek 1996; Martin and Polaszek 1999). The latter species is widely distributed in Central America and has been used in biological control programs of Aleurodicus cocois (Curtis) (Cock 1985). Some undescribed species are known from the New World. The correct identification of the parasitoids reared from pests species is essential to the success of biocontrol programs.
G. Viggiani (1986) stated new combinations for Encarsiella aleurodici from Encarsia and Encarsiella magniclava from Coccophagus. We propose a new combination—Encarsiella narroi (Gómez & García), comb.n. from Encarsia. This species was reared from Aleurodicus sp. collected on Bauhinia variegata L. and Hibiscus sp. in Mexico, Coahuila State (Gómez and García 2000). The description and illustrations of this species show characteristics belonging to Encarsiella, especially the number of setae on the mesoscutum (42 pairs according to the authors) and the structure of the antennal club. Thus, Encarsiella narroi (Gómez & García), comb.n. is the fifth species of this genus known from the New World.
Encarsiella noyesi was described from Mexico, reared from Aleurodicus dugesii Cockerell in the State of Guanajuato, and from Aleurothrixus floccosus (Maskell) on Citrus aurantifolia (Christm.) Swingle, in the State of Yucatán (Polaszek and Hayat 1992). We reared E. noyesi from Aleurodicinae whiteflies in the State of San Luis Potosí (new record for this State), and from an aleyrodid species in the State of Tamaulipas (new record for this State). In addition, a new species of Encarsiella was reared from an undetermined species of Aleurodicinae on Psidium guajava L. in the State of Tamaulipas.
The abbreviations R = radicle, S = scape, P = pedicel and F = funicle segment are used in the following description of the new species and key to the species of Encarsiella (females) of the New World.
Encarsiella tamaulipeca Myartseva and Coronado-Blanco sp. nov. (Figs. 1-3)
FEMALE (Figs. 1-2). Length: 0.75-0.82 mm (N = 8 specimens on points, 2 on slides); holotype - 0.75 mm.
Head black, face ferrugineous from anterior oculus to interantennal prominence and whitish below (except upper margin of mouth, hind part of cheeks and antennal scrobes). Pedicel and antennal club brown, scape (except distal half dorsally brown) and F3 whitish, F1-F2 pale brown. Mesosoma and metasoma black. Legs yellowish-white, middle and hind coxae, hind femur black, middle femur and hind tibia infuscate. Wings hyaline. Sheaths of ovipositor whitish.
Wider than high and as wide as mesosoma. Frontovertex 2× as wide as long, about 0.5× head width. Occipital margin slightly rounded and concave. Ocelli in slightly obtuse triangle; lateral ocelli close to occipital margin, at a distance of less than diameter of an oculus, and about 2 diameters of an oculus from eye margins. Eyes about 2× longer than cheeks. Malar sulcus present. Antenna (Fig. 1) inserted immediately under lower margin of eyes, closer to mouth margin than to eye margins. Antennal segments R-F3 and club (3-jointed) with the following ratios, length/width: R-15:9, S-60:15, P-22:13, F1-18:12, F2-25:14, F3-20:15, club-67:20. Pedicel slightly longer than F1; club slightly longer than funicle and scape. F2, F3 and club joints with two longitudinal sensilla each, sensilla absent on F1. A very thin anellus is also present.
Sculpture of dorsum with more or less hexagonal cells, sides of mesoscutum and scutellum with longitudinal cells. Mesoscutum slightly wider than long, with many setae varying in number from 54 to 64. Scutellum about 2× wider than long, with 2 pairs of long setae. Axilla with one seta, lateral lobes with three setae. Fore wing more than 2× longer than wide, marginal fringe about 0.14× wing width. Length of marginal vein equal to submarginal vein, postmarginal vein absent, stigmal vein very short. Strong setae in two rows on anterior margin form narrow bare band, interrupted near vein by a few setae (Fig. 2). Base of wing with 7-10 setae. Marginal vein with 10-13 setae, marginal fringe 2.5× maximum wing width, discal setae uniformly distributed, hind wing more than 4.5× as long as wide. Tibial spur of middle leg slightly shorter than basitarsus.
Metasoma: rounded at apex, about 0.67 times length of mesosoma (in dry specimens). Ovipositor exserted, its exserted part 0.5× length of gaster (in dry specimens); ovipositor longer than middle tibia (14:11), sheaths about 0.5× inner plates.
MALE (Fig. 3). Coloration. Similar to female in color, but face brown; legs black, except apices of fore and middle femora, apices of fore and hind tibiae, and the apical half of mid tibia and tarsi which are whitish.
Antenna (Fig. 3) inserted at level of lower eye margin, at equal distance from margins of eye and mouth. Funicle 4-segmented, club 2-segmented. Antennal segments with the following ratios length/width: R-11:8, S-50:13, P-17:13, F1-31:14, F2-36:15, F3-35:15, F4-34:16, F5-35:16, F6-34:13. Pedicel slightly less than 0.5× F1; club as long as the two preceeding segments together. F1-F6 with 3 longitudinal sensilla each. Forewing with bare base. Mesoscutum wider than long; scutellum about 1.5× wider than long.
Diagnosis. Using the key and the revision of Encarsiella species of the world provided by Polaszek and Hayat (1992), E. tamaulipeca sp. nov. is close to E. aleurodici in coloration of body and antenna, and also the following morphological features: long pedicel (P > F1) and club (>F1-F3), absence of sensilla on F1, and setaceous wing base. It differs from E. aleurodici in the following: female with antennal anellus and anterior margin of fore wing with bare band; length of marginal vein equal to submarginal vein, and marginal fringe longer (0.14× maximum wing width) (in aleurodici it is very short), ovipositor slightly longer than mid tibia (14:11); male antennal club equal to lengths of two preceeding segments.
Material Examined. Holotype, female: Mexico, Tamaulipas, Ciudad Victoria, ex Aleyrodidae on Psidium guajava, 7-8-XII-1995, E. Chouvakhina; paratypes: same data as holotype, 6 females (all on points); 27-X-1999, S. Myartseva, 1 female, 1 male, on slides.
The holotype and one paratype are deposited in the National Museum of Natural History, Washington, D.C., USA; two paratypes in the Department of Zoology, Institute of Biology, National Autonomous University of Mexico, Mexico City, D.F., Mexico; two paratypes in the Zoological Institute, Russian Academy of Sciences, St. Petersburg, Russia; one paratypeon point and one female and one male on slides in the Insect Museum, Universidad Autónoma de Tamaulipas, Ciudad Victoria, Tamaulipas, Mexico.
Etymology. Encarsiella tamaulipeca is named after the State of Tamaulipas where it was discovered.
Mexico, San Luis Potosí, Xilitla, ex Aleyrodidae, 10-XI-1999, S. Myartseva, 16 females, 17 males, MIFA (UAT); Tamaulipas, Jaumave, ex Aleyrodidae, 36 females, 2 males, 30-IV-2000 (S. Hernández-Aguilar); USA, California, Riverside, UCR Quarantine culture, A. Briones, emerged 3-IV-2000 from Aleurodicus dugesii Cockerell, 7 females, 1 male, orig. from Mexico, Jalisco, Guadalajara, 5-V-1997 (D. Headrick).
Morphological differences were observed among populations of Encarsiella noyesi reared in several regions. For example, Mexican specimens are different from those described by Hayat, who studied specimens reared from June to August from Trinidad, St. Vincent and Tobago. The Mexican specimens are smaller (female body length 0.52-0.67 mm, male 0.45-0.62 mm) and some females have only the F3 pale yellow (also observed in specimens from California). Living female specimens have a violet-bluish face and pearlish-bluish-white scutellum. Dry female specimens are lighter yellow than the Californian specimens and the basal third of the mesopleurum is black; P equal to F1; and F1 usually has longitudinal sensilla (Figs. 4-6) (also observed in specimens from California); lateral lobes with three setae; marginal fringe of forewing longer (0.14× wing width); and ovipositor exserted and slightly longer than midtibia. Male specimens have F2-F4 more pallid and pedicel length about 0.5× F1.
Key to Females of Encarsiella Species of the New World
1.Scutellum entirely black
2.Discal setae on forewing uniformly distributed; marginal vein longer than submarginal vein. Ovipositor as long as mid tibia
—Forewing with a long band bare of setae along anterior margin (Fig. 3); marginal vein equal to submarginal vein in length. Ovipositor 1.3× longer than mid tibia
3.Mesoscutum entirely dark. F1 less than 2× as long as wide. Club slightly less than 3× as long as wide. Forewing with 2 large setae on submarginal vein
—Mesoscutum pale, excluding the anterior edge and notauli. F1 2.4× as long as wide. Club slightly less than 2× as long as wide. Forewing with 2 large setae and 2-4 smaller setae on submarginal vein
4.Base of forewing with an infuscated area. Antennal scrobes and clypeus entirely pale; pedicel and scape entirely pale
—Base of fore wing hyaline. Antennal scrobes and clypeus completely dark; pedicel and scape partly or entirely dark
5.Forewing with a long band bare of setae along anterior margin and without asetose area below stigmal vein. F1 without sensillum and F2 somewhat longer than F1 and F3.
—Forewing without a long band bare of setae along anterior margin and with asetose area below stigmal vein. F1 with one sensillum, F1-F3 of about equal length
The authors thank V. A. Trjapitzin (Universidad Autónoma de Tamaulipas, Ciudad Victoria, Mexico and Zoological Institute, Russian Academy of Sciences, St. Petersburg, Russia) for valuable consultations; M. Hayat (Department of Zoology, Aligarh Muslim University, Aligarh, India) and G. A. Evans (Entomology and Nematology Department, University of Florida, Gainesville, Florida, USA) for sending important articles on the Aphelinidae and also for reviewing the manuscript; Mrs. E. Ya. Chouvakhina, who collected specimens of this new species; S.V. Triapitsyn (University of California, Riverside) who supplied specimens of Encarsiella noyesi and for critically reviewing an earlier version of this manuscript. CONACyT, Mexico, through the “Cátedras Patrimoniales de Excelencia” Program, and Research Project 31620-B, provided funding.