Dasysyrphus lotus (Williston)

Locke, Michelle M. & Skevington, Jeffrey H., 2013, Revision of Nearctic <i> Dasysyrphus </ i> Enderlein (Diptera: Syrphidae), Zootaxa 3660 (1), pp. 1-80 : 46-48

Dasysyrphus lotus (Williston)

Figures: 10A–D, 21A

Synonyms and References:

Syrphus lotus Williston 1887: 75 (original description)

Metasyrphus lotus

Fluke 1933: 108 (key, redescription and transfer to Dasysyrphus )

Dasysyrphus lotus

Stone et al. 1965: 564 (catalogue and transfer to Dasysyrphus )

Vockeroth 1992: 67 (key and redescription)

Diagnosis: Abdominal maculae do not cross abdominal margin; maculae on tergites 3&4 oblique and usually meet in the middle; face and gena continuously light ( Figs 10A & B ).

Redescription:

Body Length: 9.4–11.7mm; Wing Length: 8.7–11.4mm

Head: Frons dark with light pollenose fascia (in males it runs along ventral edge of where eyes meet, in females it is complete and>½ the length between the antennae and ocelli) and dark pile; face light with dark vitta ¼–⅓ the width of the face and does not reach the antennal socket, face with light pile lateral to the eye, sometimes dark pile along fascia or dorsally, near frons; gena light ( Fig. 10B ) with light pile; occiput dark, covered in dense, light pollen, pile light, some with some dark; scape, pedicel and flagellomere dark.

Thorax: Scutum dark, may appear shiny or metallic, pile light; scutellum light with light pile along anterior edge, dark posteriorly; wing cell c and r 1 bare at base, br bare above spurious vein and small to large areas below, bm bare on most of anterior half, and cup bare under CuP ( Fig. 10C ); haltere light; pro- and mesofemora ⅓–½ dark basally ½–⅔ light apically, metafemur ⅔–¾ dark basally, ¼–⅓ light apically, tibiae light, tarsi light, metatarsi with dark anterior side.

Abdomen: Maculae on tergite 2 large and triangular (lateral edge flattened and medial edge with rounded point), ⅓–<½ width of tergite, maculae on tergites 3&4 are oblique and fairly straight, usually meeting medially, fairly uniform in thickness, narrowing toward medial edge slightly, maculae do not reach abdominal margin ( Figs 10A & B ); sternites light with dark fasciae, anterior edge of fascia on sternite two usually angled forming a point in the centre.

Male Genitalia: Surstylus more or less triangular in shape in lateral view, with posterodorsal edge rounded, long pile on posterolateral surface, spines on anteroventral edge; cercus oval with long pile over entire surface; gonostylus hook-shaped with few pile on dorsal surface; basiphallus elongate, basally bent at about a 90 degree angle towards dorsum, apical end curved ventrally and fully sclerotized all the way around without pile or spines; distiphallus elongate, apical end flared out into small horn, which is mostly sclerotized but membranous at apex with minute setulae dorsally, basally curved towards dorsum and not enlarged ( Fig. 10D ).

Intraspecific variation: Abdominal maculae on tergites 3&4 usually meet medially, but sometimes they are completely separated from each other.

Etymology: The word lotus is Latin, meaning washed.

Distribution: Southwestern USA (AZ, CA) and Mexico ( Fig. 21A ).

Ecology: Collected from March to November at elevations from 1524–2743m.

Discussion: Williston (1887) discusses two different specimens of D. lotus in his species description. The first, the type, and another that he speculates is “allied” with the first. This second specimen is reported to have several differences, mainly the shape of the abdominal maculae and gena colour. Williston (1887) describes this second specimen as having a “black stripe on the cheeks” and he describes the abdominal maculae as being “more oblique, and strongly concave in front” and “more convex behind”. In 1895 Snow describes this lotus variation as D. creper . Fluke (1933) states that most published records of lotus probably refer to creper and that most of the specimens identified as lotus agree with Williston’s (1887) variation (the female from New Mexico). Fluke postulates that the specimen might be teneral due to the light head, but then goes on to say that it does not explain the differently shaped maculae. Curran’s (1925) redescription of lotus also refers to creper . It is clear from the description of the abdominal maculae and the figure that he was not looking at Williston’s (1887) lotus .

Dasysyrphus lotus COI data has a high mean intraspecific variation of 3.09% ( Table 2). In the NJ tree ( Fig. 4), the two Nearctic specimens cluster closely together (1.34% different), while the Neotropical specimen is 3.29– 4.38% different from the others. This is highly suggestive that lotus is a complex as currently defined. With an extremely similar habitus among these three specimens as well as the 21 specimens where it was not possible to extract DNA, it can be concluded that lotus s.l. occurs from the southwestern Nearctic through to the Neotropical region, but that it likely includes at least two species. Further investigation needs to be conducted to help discern whether the Neotropical specimens are indeed a new species.

Type Material: “ Arizona,/ C.U. Lot 35”, “Acc. 19,702/ Williston”, “ Syrphus / lotus/ Will.”, red label “ Type / No. 129/ U.S. N.M.”, “Jeff Skevington/ Specimen #/ 23780”; ♀; deposited in the United States National Museum of Natural History , Washington, D.C ( USNM). (examined)

Material Examined:

Mexico: 10 Miles West of El Salto , [23.727593, -105.49364], 2743m, 10.vii.1964, 2♂, CNCD 26391 , 26392 , J.F. McAlpine ( CNC). Amecameca , [19.119148, -98.764597], ix.1900, ♂, USNM ENT 35111 , O.W. Barrett ( CNC). Atlacomulco , 8.x.1954, ♂, JSS 21093, R . Dreisbach ( MSUC) . United States of America: Arizona: COCHISE CO .: Carr Canyon , [31.440158, -110.289641], 1524m, 29.x.1967, ♂, CNCD 26388 , 2♀, CNCD 26393 , 26394 , R . F. Sternitzky ( CNC); Ramsey Canyon , [31.447697, -110.307712], 10.iv.1967, ♀, CNCD 26397 , 12.vi.1967, 2♀, CNCD 26395 , 26396 , 28.vii.1967, CNCD 60065 , 1-15.ix.1967, ♂, CNCD 26389 , 1–8.x.1967, ♀, CNCD 26398 , 15.xi.1967, ♂, CNCD 106795 , R . F. Sternitzky ( CNC); 23.ix.1994, ♂, JSS 18303, J.E. O’Hara ( CNC); Miller Can. , 3.v.1948, ♂, JSS 23760, A.L. Melander ( USNM). SANTA CRUZ CO .: Canelo , [31.542591, - 110.514478], 1372m, 17.iii.1967, ♂, CNCD 26390 , R . F. Sternitzky ( CNC). PIMA CO .: Mount Lemmon, San Catalina Mountains , [32.443131, -110.788429], 2377m, 29.vii.1917, ♀, CNCD 26399 , ( CNC). California: ELDORADO CO., Blodgett Experimental Forest , [38.87882, -120.659071], 7.vi.1975, ♂, JSS 18302, D. Voeatlia ( CNC) .

Figures

FIGURE 10. Dasysyrphus lotus: A: female (CNCD 26389) dorsal habitus; B: female (CNCD 26389) lateral habitus; C: wing base (CNCD 26397); D: lateral view of male (JSS 18303) genitalia. Dorsal and lateral habitus scale bar = 1mm, genitalia and wing scale bar = 500µm.

FIGURE 21. Dasysyrphus species range maps (symbols indicate specimen point data). A: D. lotus (squares) and D. nigricornis (circles); B: D. occidualis; C: D. pacificus; D: D. pauxillus (circles) and D. pinastri (squares).