Eosphaerophoria marginata Frey
Species similar to Eosphaerophoria vietnamensis with 2nd abdominal tergum black dorsally and 5th tergum with 2 lateral yellow maculae. Eosphaerophoria marginata differs from E. vietnamensis in having a medial broad black vitta on frons reaching antennal bases. Moreover, Eosphaerophoria marginata has bigger yellow maculae on 5th abdominal tergum and narrower yellow fascia on 3rd and 4th terga. Male genitalia is also very similar between these two species, but E. marginata has the right superior lobe broader and without a posterior tooth being very different from left superior lobe.
Male. Head. Face straight, with distinct round tubercle, yellow, yellow pilose; gena yellow; lunula black; frons completely black on dorsal 1/2 (length between anterior ocellus and lunula), yellow on basolateral 1/2 with medial black vitta narrowing ventrally, about 1/3 of the facial width at the narrowest point, with frontal sulcus defining dorsal completely black area, with few short yellow hairs ventrally; dichoptic; vertex and vertical triangle black; ocelli brownish; antenna yellow, basoflagellomere darker dorsally, oval; arista dark brown; occiput mainly black, yellow ventrally, yellow pilose.
Thorax. Scutum mainly black, shiny medially, black pollinose laterally, yellow laterally with a lateral broad yellow stripe from postpronotum to scutellum with some black hairs, golden brown pilose; postpronotum yellow; notopleuron yellow with distinct posterolateral obtuse protuberance; scutellum triangular, yellow with dor- somedial triangular black area continuing from posterior mesonotum, brownish pilose; propleuron, anepisternum and anepimeron entirely yellow; katepisternum black with dorsal yellow macula; meron black; katepimeron yellow; katatergum mainly yellow, black posteriorly; calypter dark brown; halter orangish yellow. Wing. Wing bare basomedially. Legs. Pro- and mesoleg entirely yellow, except distal part of mesofemur and basal part of mesotibia dark, yellow pilose except tarsi with short black setulae ventrolaterally; metacoxa and trochanter yellow; metafemur yellow on basal 1/2, black on distal 1/2; metatibia black; metatarsus black, golden yellow and black pilose.
Abdomen. Dorsum mainly black, black pilose except 1st tergum and anteriorly 2nd tergum yellow pilose laterally; 1st tergum black, yellowish on basal and lateral margin; 2nd tergum black dorsally, narrowly yellow laterally on basal 3/4 continuing the yellow margin of 1st tergum; 3rd tergum black with basoanterior very narrow black fascia not reaching margins and with basal narrow yellow fascia (about 1/5 of tergum length) produced posteriorly in a medial small triangular emargination, with lateral margin yellow on anterior 1/2; 4th tergum similar to 3rd, black with ba- soanterior very narrow black fascia not reaching margins and with basal yellow fascia produced posteriorly in a medial small triangular emargination, broader than yellow fascia of 3rd tergum (about 1/4–1/3 of tergum length), with lateral margin yellow on anterior 1/2; 5th tergum black with 2 lateral triangular yellow maculae on basal 1/3, leaving median 1/2 or more black; 6th tergum yellowish, black medially; sterna yellowish, yellow pilose except 4th sternum with some long thin black hairs medially on posterior margin; 3rd sternum slightly produced medially into a projection with 2 tips narrowly separated with black setulae close to posterior margin; 4th sternum with posterior margin produced medially into 2 projections with black setulae; male genitalia as figured.
Female. Paralectotype female lacks the head, but some details are known from original description. Similar to male except for normal sexual dimorphism and face yellow with a medial black vitta. Legs: probasitarsomere dark yellow, darker than other tarsomeres; metafemur slightly more yellow basally, about 3/5, black on apical 2/5. Abdomen: 3rd and 4th terga similar to male but anterior yellow fascia narrower and posterior emargination smaller; 5th tergum with 2 long yellow maculae on anterior 1/2, leaving a narrow black fascia medially on anterior margin; 6th tergum black. Sterna yellow pilose, with black pile after 5th sternum.
Variation. Examined paralectotype male has the 4th abdominal tergum broken, placed in a microvial with the genitalia and the rest of the terga. The non-examined paralectotype male lacks the head.
The female from Thailand presents some variation compared with the female from the Philippines: face yellow with medial black vitta narrowing down to oral apex; frons completely black on dorsal 1/4 (length between anterior ocellus and lunula), yellow on basolateral 3/4 with a media broad black vitta, about 3/4 of the facial width, without frontal sulcus. Scutellum with few short black pile on posterior margin. Mesotibia with a medial small yellowish macula, not well-defined and could be the result of the use of forceps to arrange the legs. Abdomen similar except 5th tergum with a smaller yellow maculae, leaving median 1/3–1/2 black.
Length (2): body, 5.6–6.2 (5.9) mm; wing, 4.0–4.8 (4.4) mm.
Originally described from Philippines, it is also found in Thailand.