Citrogramma, VOCKEROTH, 1969

Mengual, Ximo, 2012, The flower fly genus Citrogramma Vockeroth (Diptera: Syrphidae): illustrated revision with descriptions of new species, Zoological Journal of the Linnean Society 164 (1), pp. 99-172 : 101-104

GENUS CITROGRAMMA VOCKEROTH, 1969

Type species: Syrphus hervebazini Curran, 1928 by original designation.

Vockeroth, 1969: 92, map 14, figs 7, 16, 56, 57, 58, 93, 94, 95. Knutson et al., 1975: 311; Kapoor, Malla & Rajbhandari, 1979: 52; Datta & Chakraborti, 1985: 240; Thompson & Vockeroth, 1989: 442; Wyatt, 1991: 155–169, figs 1–16; Sun 1992: 1106; Ghorpadé 1994: 5; Yang, Huang & Cheng, 1998: 136; Rojo et al., 2003: 42; Ohara, 2004: 830; Mitra, Mukherjee & Banerjee, 2008: 3; Mengual et al., 2009: 7, 8, 21; Mengual & Ghorpadé, 2010: 44, 45, figs 1, 2.

Olbiosyrphus of Hervé-Bazin, 1923a, b, 1926; Frey, 1946.

Syrphus of de Meijere, 1908 (in part), 1914 (in part); Hervé-Bazin, 1923a; Curran, 1928 (in part), 1931a (in part), 1931b (in part), 1942 (in part); Shiraki, 1930.

Xanthogramma of Matsumura, 1916 (in part); Brunetti, 1923; Shiraki, 1930 (in part); Hull, 1949; Keiser, 1958; Nayar & Nayar, 1965; Biswas, Lahiri & Ghosh, 1975; Knutson et al., 1975 (in part).

Description (adapted from Vockeroth, 1969: 92) Rather small to large, slender to robust species.

Head: Face with tubercle, gradually sloping dorsally, more abrupt ventrally, pilose; mouthparts normal; eye bare; male holoptic; antenna short, shorter than face; basoflagellomere short, roundish to oval; ocellar triangle equilateral; occiput densely pilose.

Thorax: Scutum with broad, complete bright yellow lateral margin; disc black with fine brownish/bluish subshining pollinosity, sometimes also with shining bluish medial and/or submedial vittae or (perhaps only in slightly wetted specimens) entirely opaque black. Postpronotum bare. Scutellum simple with dark subscutellar fringe. Metasternum pilose with some long hairs, bare only in C. quadricornutum Vockeroth, 1969 . Wing: usually entirely microtrichose, partly bare basally in some species; vein R 4+5 straight, without appendix; crossvein r-m basal; vein M 1 sinuate, processive; vein M 2 present, short. Alula normal, broad, microtrichose. Legs: normal, not modified.

Abdomen: Usually elongate oval, parallel-sided; slightly margined from middle of tergum 2 to end of tergum 5, but sometimes with margin greatly reduced, e.g. in C. quadricornutum present only on tergum 5; terga 3 and 4 with an entire sub-basal yellow fascia. Male genitalia. Very variable.

Etymology

Citrogramma is derived from the neuter adjective citro, from the Greek (kitrion, kitron), meaning ‘citron-yellow, of citron’ ( Brown, 1956: 206), and the neuter noun gramma, from the Greek (gramma, -tos), meaning ‘mark, written character, line’ ( Brown, 1956: 378). Thus, Citrogramma refers to the lateral yellow vitta of the scutum present in all species of the genus. Vockeroth (1969) did not indicate the gender of Citrogramma , but he used a neuter form for the species epithet of his new species, e.g. bicornutum , notiale , quadricornutum , and sedlacekorum . Vockeroth also changed the species epithet of the previously described species without neuter termination, i.e. clarum , difficile , and variscutatum . According to Article 30.2.3 of the International Code of Zoological Nomenclature (ICZN, 1999), Citrogramma must therefore be treated as of neuter gender, and all new species names follow this gender except nouns in apposition. For previously described species, the original masculine or feminine is converted to neuter form, following Article 34.2 of ICZN (1999).

Biology

Only one prey species has been cited for Citrogramma , the brown citrus aphid or Toxoptera citricida (Kirkaldy, 1907) ( Hemiptera : Aphididae ) ( Michaud, 1999). This citation, however, is a mistaken assumption, as also suggested by Rojo et al. (2003), because C. citrinum , cited as Syrphus citrinum ( Brunetti, 1923) , is not found in Florida ( USA) from where Michaud documented the record. Michaud was contacted, the voucher specimen for this record examined, and it did not belong to Citrogramma .

A specimen of Citrogramma amarilla Mengual sp. nov. from Shillong (Meghalaya, India) has a label with the annotation ‘Found resting on Pine with aphid attack’. This note suggests that some species could be aphidophagous. A female specimen of C. notiale was collected ‘among Araucaria cunninghamii ’. There are also two specimens of C. circumdatum collected from a logging area (Bulolo, Papua New Guinea) with the note: ‘ Castanopsis /Bamboo forest’, and four species with individuals collected in ‘moss forest’: Citrogramma difficile , C. fascipleurum , Citrogramma hervebazini , and C. vockerothi .

A reared female of C. notiale , found on Ageratum houstonianum Mill. (Asteraceae) in Samsonvale ( Australia, Queensland), was studied and to my knowledge it is the only Citrogramma puparium known (see Figs 124–126 ). Finally, in the original description of C. notiale, Vockeroth (1969) cited a paratype female from Sydney ( Australia, New South Wales) collected by McIvor in tunnels of Bostrychopsis jesuita (Fabricius, 1775) ( Coleoptera : Bostrichidae ), in a wasp’s nest. However, so far, nothing is clearly known of the biology of these flower flies.

Distribution

Citrogramma is found in Oriental (Indomalayan) and Australasian biotic regions, crossing Wallace’s line, and in the southern provinces of China (see Fig. 2 ). Biogeographical or faunal regions provide a means for categorizing the main features of the distribution of existing animals or plants but there is a considerable controversy about the reality and practicality of them because limits of faunas and floras do not correspond exactly to certain geographical or political boundaries. Biotic regions are only a pragmatic instrument to represent the average patterns of animal distribution, making ‘standard’ units for comparison purposes only ( Thompson, 1972). Thompson (1999b) pointed out that only three countries, China, Indonesia, and Mexico, extend across biotic regional boundaries. For these countries, he used political subunits to draw the boundaries. As Thompson (1999b) mentioned, this separation is not the most accurate.

The genus Citrogramma has been cited from Sichuan Province (Palaearctic China) and recently found in Tibet (K. Huo pers. comm.). Based on the original work of Wallace (1876), Delfinado & Hardy (1973) included the southern region of Sichuan in the Oriental Region ‘... mingling with the Palaearctic fauna in the mountains south of the Yangtze River...’. Citrogramma specimens from Sichuan and Tibet were collected in the southern areas of these provinces, close to Yunnan Province ( China) and Arunachal Pradesh ( India), respectively. Thus, following the political boundaries in Thompson (1999b: 51, 63), Citrogramma is present in the Palaearctic Region.

Specimens are here reported from Nepal, India, Sri Lanka, Myanmar, Thailand, Malaysia, Vietnam, Laos, Taiwan, Indonesia, Philippines, China [Tibet (Xizang), Yunnan, Fujian, Sichuan, Hainan], Papua New Guinea ( PNG), Solomon Islands, New Caledonia, and Australia (see below in each species’ description). Material collected in Hainan Province and Tibet was studied and identified by Huo. New specimens and species from New Caledonia, Taiwan, Nepal, and China expand the geographical distribution of Citrogramma .

Citrogramma species are found in nine different biodiversity hotspots ( Myers et al., 2000; Mittermeier et al., 2005), including the Western Ghats, Sri Lanka, Himalaya, Indo-Burma, Sundaland, Wallacea, Philippines, East Melanesian Islands, and New Caledonia. By definition, New Guinea Island is not a hotspot but it has the highest known diversity of the genus Citrogramma in number of species: a total of 15 described species and two other not formally described species, plus another species, C. solomonense , found in Boungainville and New Britain islands (two provinces of PNG but not New Guinea Island). Similar high species diversity in New Guinea was reported for the syrphid genus Eosphaerophoria Frey, 1946 ( Mengual & Ghorpadé, 2010).

Diagnosis

The genus Citrogramma is recognized amongst the syrphines (subfamily Syrphinae , tribe Syrphini ) by the following combination of characters: (1) scutum with lateral broad yellow vitta; (2) metasternum pilose (except Citrogramma quadricornutum ); (3) abdomen margined; (4) scutum black with medial brown or olivaceous pollinosity, usually with submetallic area divided into vittae or not; and (5) subscutellar fringe present.

Species groups of Citrogramma

Vockeroth (1969) mentioned that species of this genus show much greater variation in the male terminalia than do those of any other genus of the Syrphini . Although the male genitalia are very variable in Citrogramma , there are some similarities like sternum 9 being unusually reduced. Based on male genitalia characters, Citrogramma species can be divided into three groups: (1) species with overall male genitalia similar or identical to C. henryi ( Figs 129, 130 ); (2) species with a slight variation in male genitalia compared to the male genitalia of C. henryi , e.g. C. robertsi ( Fig. 149 ) or Citrogramma schlingeri ( Fig. 141 ); and (3) species with male genitalia that are very different compared to male genitalia of C. henryi , e.g. C. bicornutum or C. quadricornutum ( Figs 140 , 153 ).

After checking the male genitalia of all the Citrogramma species , most of them have similar male genitalia, identical to C. henryi (see Figs 127–130 ). As a result of this fact, male genitalia characters are not useful in describing species if they do not belong to the groups 2 or 3, and it is also the reason why most of the time male genitalia characters were not used in the identification key. However, there are a few species that only differ by the male genitalia; those are the cases of C. notiale and Citrogramma australe ( Australia) , Citrogramma pintada and Citrogramma pinyton ( Papua New Guinea), or Citrogramma schlingeri , Citrogramma distinctum , and Citrogramma triton ( Papua New Guinea). These are cryptic species with the same morphology and different male genitalia living in the same geographical area, and recent speciation could explain the small amount of morphological variation.

As to morphological characters, there are a few species groups that can be recognized: (1) the C. notiale species group, with C. notiale , C. australe , C. asombrosum , C. bicornutum , and C. quadricornutum (probably including C. sedlacekorum , C. quadratum , and others); (2) the C. luteifrons species group, with C. luteifrons , C. luteopleurum , C. schlingeri , C. distinctum , C. pinyton , C. triton , and C. pintada ; (3) the C. clarum species group, with C. clarum , C. amarilla , C. sp. B, C. matsumurai , C. frederici , and possibly some others; (4) the C. citrinum species group, with C. citrinum , C. citrinoides , C. chola , C. henryi , and C. flavigenum ; and (5) the C. gedehanum species group, with C. gedehanum , C. variscutatum , C. wyatti , C. currani , C. fascipleurum , and C. difficile . None of these five species groups deserve a supraspecific category, except to note that species in the same group are more morphologically related to any other species placed in another group. Some species are not included in these groups, such as C. hervebazini or C. shirakii , both with very similar and distinct male genitalia.

Figures

Figure 2. World distribution of Citrogramma Vockeroth. The limit shown is only an approximation defined by collecting points for specimens examined.

Figures 122–130. 122–123, Citrogramma frederici: 122, frontal view of female head; 123, dorsal view of female abdomen. 124–126, Citrogramma notiale species group: 124, lateral view of puparium; 125, dorsal view of puparium; 126, posterior view of posterior breathing tube and spiracular openings (detail). 127, Citrogramma citrinum, left lateral view of male genitalia. 128–129, Citrogramma henryi: 128, left lateral view of male genitalia; 129, tergum 9 and surstyli, dorsal view. 130, C. henryi (from Vockeroth, 1969 as C. citrinum): a, left lateral view; b, superior lobe, lateral, outline only; c, sternum 9, superior lobes and aedeagal base, ventral view.

Figures 145–150. Male genitalia. 145, Citrogramma matsumurai, left lateral view. 146, Citrogramma wyatti, left lateral view. 147–148, Citrogramma pennardsi: 147, left lateral view; 148, tergum 9 and surstyli, dorsal view. 149, Citrogramma robertsi, left lateral view. 150, Citrogramma quadratum, left lateral view.

Figures 140–144. Male genitalia. 140, Citrogramma bicornutum (from Vockeroth, 1969): a, left lateral view; b, superior lobe, lateral, outline only; c, sternum 9, superior lobes and aedeagal base, ventral view; d, right surstylus, lateral view. 141, Citrogramma schlingeri, left lateral view. 142, Citrogramma distinctum, left lateral view. 143, Citrogramma triton, left lateral view. 144, Citrogramma frederici, left lateral view.

Figures 151–153. Male genitalia. 151, Citrogramma hervebazini (from Vockeroth, 1969): a, left lateral view, surstylus outlined only; b, superior lobe, lateral, outline only; c, sternum 9, superior lobes and aedeagal base, ventral view; d, left surstylus, lateral view. 152, Citrogramma shirakii, left lateral view. 153, Citrogramma quadricornutum (from Vockeroth, 1969): a, left lateral view (sternum 9 mostly hidden); b, superior lobe, lateral, outline only; c, sternum 9 and genitalia, left lateral view; d, tergum 9 and cerci, dorsal view; e, sternum 9, superior lobes and aedeagal base, ventral view; f, right surstylus, lateral view.