Pediobius cajanus, Taveras & Hansson, 2015

Taveras, Rosina & Hansson, Christer, 2015, Pediobius cajanus sp. n. (Hymenoptera, Eulophidae), an important natural enemy of the Asian fly (Melanagromyza obtusa (Malloch )) (Diptera, Agromyzidae) in the Dominican Republic, Journal of Hymenoptera Research 45, pp. 41-54 : 44-47

Pediobius cajanus sp. n.

Figures 6-12 , 13-14 , 15-19

Material examined.

Type material: HOLOTYPE ♀ labelled " DOMINICAN REPUBLIC: San Juan Province, San Juan de la Maguana, 20.x.2014, Rosina Taveras", "Ex pupae of Melanagromyza obtusa on pigeon pea ( Cajanus cajan )" (in the Natural History Museum, London, United Kingdom ) . PARATYPES: 42♀ 15♂ with same label data as holotype (in the Natural History Museum , London , United Kingdom ; Canadian National Collection of Insects and Arachnids , Ottawa , Canada ; Museo Nacional de Historia Natural , Dominican Republic ; Museum of Biology ( Entomology ), Lund , Sweden; United States National Museum of Natural History, Washington, D.C., USA) . Additional material: 42♀ 12♂ from the Dominican Republic: Luperon Province, Puerto Plata, v.2013 (in the Museum of Biology ( Entomology ), Lund , Sweden ) .

Diagnosis.

Hind leg with tibial spur 0.4 times as long as length of hind tarsus; propodeum with strong submedian carinae that diverge towards posterior part (Fig. 18 ); propodeal callus with four setae; female gaster elongate (Figs 13 , 19 ), 2 times as long as wide; small species (0.9-1.5 mm).

In the most recent keys to the Neotropical species of Pediobius (see Hansson 2002) and in the key to Nearctic species ( Peck 1985), P. cajanus runs to P. pyrgo (Walker, 1839). It differs from P. pyrgo in having median third of scutellum smooth (Fig. 17 ) (completely reticulate in P. pyrgo ), posterior margin of dorsellum tridentate (Fig. 18 ) (rounded in P. pyrgo ), and petiole in female 0.7 times as long as wide (1.0 times as long as wide in P. pyrgo ).

Pediobius cajanus sp. n. also appears to be morphologically similar to P. vignae (Risbec, 1951) from Nigeria, as described in Kerrich (1973). The host of P. vignae , Melanagromyza vignalis Spencer, 1959 in seeds of Vigna unguiculata (L.) Walp. ( Fabaceae ), is also similar to the host of P. cajanus . When Kerrich (1973) revised the tropical and subtropical species of Pediobius he was unable to find the type material of P. vignae and designated a neotype for the species, to be deposited in BMNH. However, this neotype, or the series it was pulled from, cannot be located in BMNH (Natalie Dale-Skey, pers. comm.). Thus we rely totally on the redescription of P. vignae in Kerrich (1973) for the interpretation of this species. Pediobius cajanus sp. n. differs from P. vignae in having eyes bare (Figs 15 , 16 ) (setose in P. vignae ), scutellum smooth in median third (Fig. 17 ) (reticulate throughout in P. vignae ), female first gastral tergite 0.5 times as long as length of gaster (Figs 13 , 19 ) (well over half the length of gaster in P. vignae ), female with first gastral tergite with very weak and superficial reticulation posteromedially (Figs 13 , 19 ) (this part with strong and very distinct reticulation in P. vignae ).

Description.

Female: length of body 1.1-1.5 mm.

Antenna dark and metallic (Figs 6 , 11 ). Frons dark golden-purple with bluish tinges (Fig. 8 ). Vertex shiny with dark golden and blue tinges (Fig. 10 ). Pronotum with part in front of transverse carina dark golden-purple, part behind transverse carina metallic bluish-green (Fig. 13 ). Mesoscutum dark golden-purple (Fig. 13 ). Scutellum dark golden-purple with lateral and posterior parts with greenish tinges (Fig. 13 ). Propodeum golden-green (Fig. 13 ). Coxae, femora and tibiae dark and metallic (Fig. 6 ); tarsal segments 1-3 dusky on fore leg and white on mid and hind legs, fourth segment dark brown on all legs. Wings hyaline. Petiole dark golden-purple. Gaster with first tergite metallic bluish-green in anterior fourth, posterior three quarters and remaining tergites dark golden-purple (Fig. 13 ).

Antenna as in Figs 6 , 11 . Frons smooth and shiny below level of toruli and above frontal suture, between these parts with very weak reticulation (Fig. 16 ); antennal scrobes join frontal suture separately (Fig. 8 ). Vertex inside and behind ocellar triangle with weak, small-meshed reticulation, outside ocellar triangle smooth (Fig. 15 ). Occipital margin with a weak carina behind posterior ocelli, otherwise rounded (Fig. 15 ). Eyes bare (Figs 15 , 16 ). Ratios: length of head (in dorsal view)/width of head (measured at widest part): holotype 0.49, paratypes 0.46-0.52; height of eye in frontal view/malar space: holotype 2.06, paratypes 1.87-2.33; height of eye in frontal view/width of mouth opening: holotype 1.45, paratypes 1.29-1.46; distance between posterior ocelli/distance between eye and posterior ocellus: holotype 2.38, paratypes 1.75-2.40

Mesoscutum with weak reticulation (Fig. 17 ), meshes isodiametric in anteromedian part but otherwise elongate; notauli distinct and narrow in anterior two thirds, indistinct in posterior third. Scutellum convex with median third smooth, lateral parts to either side of smooth, median part reticulate with elongate meshes (Fig. 17 ). Posterior margin of dorsellum with a prominent medial projection and with weak and blunt lateral projections (Fig. 18 ). Transepimeral sulcus strongly curved. Fore wing speculum closed below; 12 admarginal setae. Hind leg with tibial spur 0.4 times as long as length of hind tarsus. Propodeum with strong submedian carinae that diverge towards posterior part (Fig. 18 ); with a short but distinct nucha; callus with four setae. Petiolar foramen rounded. Ratios: length of fore wing/length of marginal vein: holotype 1.98, paratypes 1.85-2.04; length of fore wing/height of fore wing: holotype 1.67, paratypes 1.63-1.75; length of postmarginal vein/length of the stigmal vein: holotype 0.96, paratypes 0.63-1.00.

Petiole 0.7 times as long as wide, with strong irregular sculpture (Fig. 19 ). Gaster with first tergite smooth (Fig. 19 ), posteromedially with very weak and superficial reticulation, meshes incomplete; first tergite covers 0.5 times the length of gaster in both sexes (Figs 13 , 14 , 19 ). Ratio length of the mesosoma (measured along the median mesosoma from the pronotal collar carina to posterior margin of the propodeum)/length of gaster: holotype 0.88, paratypes 0.81-0.93.

Male: length of body 0.9-1.3 mm.

Similar to female except as follows. Frons bright metallic bluish-green (Fig. 9 ). Mesoscutum golden-green (Fig. 14 ). Scutellum golden-green (Fig. 14 ). Gaster with first tergite metallic bluish-green in anterior half, posterior half and remaining tergites dark golden-purple (Fig. 14 ).

Antenna as in Figs 7 , 12 . Ratios: height of eye in frontal view/malar space: 1.75-1.94; height of eye in frontal view/width of mouth opening: 1.30-1.60.

Petiole 1.1 times as long as wide. Gaster with first tergite completely smooth. Ratio length of the mesosoma (measured along the median mesosoma from the pronotal collar carina to posterior margin of the propodeum)/length of gaster: 1.09-1.58.

Etymology.

Named after the host plant.

Distribution.

The Dominican Republic. The first author of this paper has reared this new species from its host from 90 sites (Fig. 5 , Table 1 ).

Biology.

Pediobius cajanus sp. n. is a gregarious endoparasitoid in pupae of Melanagromyza obtusa . The female wasps lay 3-15 eggs per fly pupa (mean = 7.6, n = 50). In laboratory conditions, with 25 °C, the development time from egg to pupa of the parasitoid was 21 days. Without food the female wasps lived for four days and males for two days. The sex ratio female to male is 5:1 (n = 50).

Biology of the Asian fly.

The female fly lays eggs on immature pods, and the emerging larvae feed in the developing seeds, initially feeding externally but after the first molt feed inside the seed, which they eventually destroy (Fig. 3 ). A single seed may be enough for a larva to complete its development, but usually more than one seed is devoured. The larva goes through three stages prior to pupation. Before pupating in the seed pod the larva emerges from the seed and opens a window in the wall of the pod (Fig. 2 ).

Conclusions.

Pediobius cajanus sp. n. is so far known only from the Dominican Republic, but its distribution throughout this country suggests a larger distribution. It is certainly found over the entire island of Hispaniola, of which the Dominican Republic constitutes the larger part. It is possibly also found on neighboring islands in the Caribbean, e.g. Cuba, and perhaps also in tropical parts of the mainland in the Americas. Some Pediobius species have a very large distribution ( Kerrich 1973, Hansson 2002), thus indicating a strong dispersal ability. If this ability is present also in P. cajanus sp. n. future investigations must establish.

In the Dominican Republic P. cajanus sp. n. is an important natural enemy of the Asian fly, killing on average 25% of the fly larvae in investigated areas. The fly is found in many tropical countries, in Asia, its native area, as well as in other tropical parts of the World, and is a serious pest on economically valuable crops in these areas. The record of parasitism of P. cajanus sp. n. in the Dominican Republic makes it worthwhile to investigate the potential of this parasitoid as a biocontrol agent of the Asian fly.

Figures

Figure 5. Map of the island of Hispaniola showing localities in the Dominican Republic where Pediobius cajanus sp. n. has been reared from Melanagromyza obtusa during this investigation. Specific names of localities and coordinates are provided in Table 1.

Figures 6 - 12. Pediobius cajanus sp. n. 6 - 7 habitus in lateral view 6 female 7 male 8 - 9 head in frontal view 8 female 9 male 10 vertex, female 11 - 12 antenna in lateral view 11 female 12 male.

Figures 13 - 14. Pediobius cajanus sp. n., habitus in dorsal view 13 female 14 male.

Figures 15 - 19. Pediobius cajanus sp. n., female 15 vertex 16 head in frontal view 17 thoracic dorsum 18 propodeum in dorsal view 19 petiole and gaster in dorsal view.

Figures 1 - 4. 1 pigeon pea, Cajanus cajan (L). Millspauh 2 seed pods of pigeon pea with marks indicating windows created by larvae of the Asian fly, Melanagromyza obtusa (Malloch), prior to pupation, a window that facilitates the emergence of the adult fly from the pod 3 opened seed pods of pigeon pea with pupae of the Asian fly 4 imago of the Asian fly with pupa.