CHRYSOTOXUM Key 1.A
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CHRYSOTOXUM Key 1.a. Antennae: 3rd segment long: as long Introduction as or longer than segments 1 and 2 together (figure 244, figure 245)› 2 Chrysotoxum are wasp mimics, and often 1.b. Antennae: 3rd segment short: shorter found in association with open wood- than segments 1 and 2 together (figure lands. They appear near the ground in the 246) › 6 vegetation (e.g. C. arcuatum), on flowers (e.g. C. bicinctum), on leaves of shrubs and 2.a. Tergites 3 and 4 with short hairs, trees (e.g. C. cautum), and high up in trees shorter than the height of metatars 1, (e.g. C. octomaculatum). The precise feed- seemingly bare › 3 ing habits of the larvae of Chrysotoxum are 2.b. Abdominal tergites with long hairs, unknown (Rotheray, 1993). The larvae longer than the height of metatars 1 › 4 live in the ground, associated with ant nests and are presumably predators of root 3.a. Frons yellow; abdominal margin of aphids. There are reports of females tergites mainly yellow; antennae: seg- ovipositing near ant nests. C. bicinctum lar- ment 3 equal in length to the sum of vae have been reared on pea aphids in the segments 1 and 2. 10-14 mm. Southern laboratory, supporting the predatory life part of Central Europe › Chrysotoxum history (Rotheray, 1993). cisalpinum Rondani 3.b. Frons black; abdominal margin black and yellow; antennae: segment 3 dis- Recognition tinctly longer than segments 1 and 2 together. 10-14 mm. Central and Chrysotoxum contains broad-bodied, Southern Europe, North Africa, east to black and yellow hoverflies with long Afganistan › Chrysotoxum interme dium antennae. They mimic social wasps and Meigen Speight (2003) remarks that C. fasciolatum Jizz: blackish Chrysotoxum, yellow bands run from is a surprisingly good mimic of Vespula hind corner of side margin to the middle of the queens. The key is based on Van der Goot front margin. (1981), Sack (1932), Seguy (1961), Smit, Note: probably a species complex with more Renema and Van Aartsen (2001), and species in Southern Europe. Speight (2003). The names C. festivum and C. arcuatum have been preserved by the 4.a. Antennae: 3rd segment longer than Zoological Code Commission. segments 1 and 2 together (as figure 245); abdomen strongly arcuate; male: genitalia small, at most reaching the hind margin of sternite 4 (figure 247) › 244. 5 4.b. Antennae: 3rd segment as long as seg- ments 1 and 2 together (figure 244); abdomen relatively flat (use reference material). Male: genitalia very large, 245. reaching over the hind margin of stern- ite 4 (figure 248). Female: unique among European Chrysotoxum in pos- sessing a longitudinal, median, membra- nous strip on abdominal tergite 6, 246. which divides this tergite into 2 parts; habitus: figure 249. 12-14 mm. Europe, east to Western Siberia › Chrysotoxum cautum Harris figure 244. Chrysotoxum cautum, antenna. Jizz: large, yellowish Chrysotoxum, often suns itself figure 245. Chrysotoxum intermedia, antenna. on or patrols along leaves, wing without well- figure 246. Chrysotoxum verralli, antenna marked dark spot. (Verlinden). 83 247. 250. 248. 251. figure 250. Chrysotoxum arcuatum, abdomen, side view. figure 251. Chrysotoxum fasciolatum, wing (Verlinden). figure 247. Chrysotoxum fasciolatum, tip of abdomen from below. 5.b. Wing: front margin yellowish with a figure 248. Chrysotoxum cautum, tip of distinct dark spot in the top 1/2 (figure abdomen from below (Verlinden). 251); scutellum yellow with a broad dark hind margin; abdomen elongate, about 1.5 times as long as wide, and not that thick. 5.a. Wing: front margin hyaline, except for Larger species: 13-17 mm. Northern and the stigma, without dark spot in the top Central Europe, east to Japan, Nearctic › 1/2; scutellum yellow with a darkened Chrysotoxum fasciolatum Degeer centre; abdomen short and oval, less than 1.5 times as long as wide, in side 6.a. Abdominal tergites 2-5 have yellow, view thick (figure 250). Smaller species: usually interrupted bands of equal 9-12 mm. Northern Europe and elevat- width › 7 ed parts of Central Europe, east to Japan 6.b. Abdomen with distinct yellow bands › Chrysotoxum arcuatum Linneaus (= on tergites 2 and 4 only (figure 252), the Chrysotoxum fasciatum auctorum) other tergites black (typical specimens), Jizz: rather small, with equal coverage of black or with thin yellow bands (var. tricinc- and yellow at first glance. Often foraging and fly- tum). 10-11 mm. Europe, North Africa, ing close to the ground. east to Siberia › Chrysotoxum bicinctum Linneaus Jizz: Two strong, uninterrupted, yellow bands. In flight similar to D. tricinctus (short antennae). 7.a. Abdominal margin black, the yellow bands do not reach the margin (figure 253); wing: dark spot at the front in the top 1/2 › 8 7.b. Abdominal margin yellow and black, the yellow bands reach the margin (fig- ure 254); wing with or without dark spot › 10 8.a Antennae: 1st segment longer than the 2nd segment; femora 2 and 3: black on basal half; wing: dark spot large and elongate; abdomen elongate with paral- lel margins; scutellum: black with small yellow hind margin (figure 255). 10-12 mm. Central Europe, east to Kazakstan figure 249. Chrysotoxum cautum, habitus › Chrysotoxum lineare Zetterstedt (Verlinden). Jizz: abdomen elongate, a dark species. 84.