Eumerus figurans Walker 1859

Adomako, Abigail Kusiwaa, Gasu, Edward Ntim, Mensah, Jehoshaphat Oppong & Borquaye, Lawrence Sheringham, 2020, What do Eumerus Meigen larvae feed on? New immature stages of three species (Diptera: Syrphidae) breeding in different plants, Organisms Diversity & Evolution (New York, N. Y.) 20 (2), pp. 267-284 : 272-273

Eumerus figurans Walker 1859

( Figs. 2 ; 3b ; 4b ; 6c, d ).

Shape and size of third instar (L3) larvae ( Fig. 2 ) Subcylindrical in cross-section, posteriorly tapered, with anal segment elongated. Length: mean 6.78 mm (range 5.61– 7.48); width: mean 2.8 mm (range 2.4–3.22); height: mean 2.19 (range 1.7–3.09) (n = 3).

Head Antenno-maxillary organs on bulbous and rounded projections with a brown mark on the lateral sides; dorsal lips bearing thin and long clear setae arranged in numerous rows (13–15) and mandibular lobes without setae.

Head skeleton ( Fig. 3b ) Mandibular hooks heavily sclerotized and mandibular lobes fleshy, well-developed, fused with the mandibles; dorsal and ventral cornua almost similar in length, dorsal cornu not tapering, wider than ventral; labrum not prominent, lightly sclerotized; pharyngeal sclerite short, 1/4 the length of the dorsal cornu; tentorial arm lightly sclerotized, diffuse, ending at mid ventral cornu; tentorial bar heavily sclerotized; mandibular hooks 0.36 mm long, without accessory teeth and, in apical view, 23% more separated at the apex than the basal width.

Thorax Anterior spiracles oval, pale brown and shiny, flattened to the tip, dome apex with three openings ( Fig. 4b ). Length: mean 94 μm (range 76–112); width: mean 83 μm (range 80–87); height: mean 48 μm (range 46–50). Mesothoracic prolegs absent.

Abdomen Integument villous, covered in long triangular setae and sensilla with 2 to 4 setae each. Locomotory organs on segments 1–6, bearing fine and clear spicules, without crochets. Anal segment oriented upward, 1.18 mm long (range 0.65–1.45), ≈ 1.5 times longer than the 6th segment (mean 0.83, range 0.65–1.03), ventral surface longer than dorsal. Three pairs of lappets present, 1st and 2nd conic, 3rd longer than the others, middle ones divided into two projections. PRP: ( Fig. 6c, d ) Subcylindrical tube, sometimes not perfectly symmetrical, tapering posteriorly. α = 341 μm; β = 43 μm; α/β = 0.795. Below transverse ridge, surface coarse, with some longitudinal and transversal wrinkles; above ridge, surface punctured to smooth towards the apex; spiracular plate with 3 very sinuous openings, margins with 4 pairs of multi ramous setae.

Species distribution Commonly associated to ginger cultures, possibly widespread; from Oriental, Australasian, and Afrotropical bioregions: Bali, Borneo, Celebes, India (Rajasthan), Indonesia (Java, Sulawesi), Japan, Malaysia (Sabah /Borneo), Myanmar, Philippines (Palawan), Sri Lanka, Taiwan, Thailand, Vietnam; USA (Hawaii); Seychelles ( Evenhuis and Pape 2019; Hauser, unpublished data).

Material examined Three L3 instar larvae. #1: USA: HI , Hawaii Co. , Honokaa, ex ginger, 2009, E. figurans (immature) PDR#1509453 Det. M. Hauser Dec 2016; #2: USA: HI , Hawaii ex ginger root, 2009, E. figurans (immature) PDR#1308785, Det. M. Hauser Dec. 2016; #3: USA, HI , Honolulu Co , Honolulu ex ginger, 2009, 16 V 936 , Eumerus marginatus (immature) PDR# 1308801, Det. M. Hauser Dec. 2016. Deposited at CSCA .

Figures

Fig. 2 General shape of Eumerus figurans larva, dorsal view. Scale line = 2 mm

Fig. 3 Head skeletons of Eumerus, lateral view. a Eumerus alpinus. b Eumerus figurans. c Eumerus superbus. D dorsal cornu, L mandibular lobe, M mandibular hook, P pharyngeal ridges, T accessory tooth, V ventral cornu. Scale lines = 250 μm

Fig. 4 Anterior spiracles (AS) of Eumerus larvae and puparia, apicoventral view. a Eumerus alpinus, puparium; SEM. b Eumerus figurans, larva; stereo microscope. c Eumerus superbus, puparium; SEM. O spiracular opening. Scale lines: a = 50 μm; b = 200 μm; c = 100 μm

Fig. 6 Posterior respiratory processes (PRP) of Eumerus lar- vae and puparia in dorsal view (left) and polar view (right). a, b Eumerus alpinus, puparium; SEM. c, d Eumerus figurans, lar- va; stereo microscope. e, f Eumerus superbus, puparium; SEM. α distance from the trans- verse ridge to the center of the spiracular plate, β width of the PRP at the transverse ridge level, C* spiracular scar, O spiracular opening, R transverse ridge, S spiracular seta. Scale lines: a and e = 500 μm; b and c = 250 μm; d = 100 μm; f = 200 μm