Diamesa

Montagna, Matteo, Urbanelli, Sandra & Rossaro, Bruno, 2016, The species of the genus Diamesa (Diptera, Chironomidae) known to occur in Italian Alps and Apennines, Zootaxa 4193 (2), pp. 317-331 : 327-329

Key to species of Diamesa from the Italian Alps based on adult males

1 Antenna plumose, with 13 flagellomeres; sternapodeme arched; eyes bare or hairy; gonostylus of variable shape, never triangular or squared; wings never reduced; microtrichia on medial surface of gonostylus less dense....................... 2

- Antenna not plumose with 8 flagellomeres; sternapodeme triangular; eyes hairy; gonostylus triangular large at its base and

restricted to apex or squared; wings often reduced; medial surface of gonostylus with "pile" of microtrichia............ 19 2 Eyes hairy, that is the eye microtrichia clearly surpass the ommatidial lens and are visible along lateral eye margin....... 3

- Eyes not hairy, that is the eye microtrichia are not visible or at least not surpass the height of ommatidial lenses along lateral eye margin.......................................................................................... 9

3 Basimedial setal cluster present, in ventral position, between superior and inferior volsella........................... 4

- Basimedial setal cluster absent.......................................................................... 7

4 Superior volsella flat, not well separable from the rest of gonocoxite; gonocoxite more or less elongated, slender; basimedial setal cluster with about 12–15 very long setae, directed medially; inferior volsella elongated, with numerous long (60–70 µm), anteriorly directed setae on the distal part; gonostylus uniform without some part enlarged........................... 5

- Superior volsella rounded, well developed, clearly separable from the rest of the gonocoxite; gonocoxite not unusually long and slender; basimedial setal cluster present but with very short setae; inferior volsella not elongated, without numerous anteriorly directed setae; gonostylus with a bulbous basal part and a slender distal part about of the whole length.............. 6

5 Gonocoxite long and slender (length 400–500 µm, breadth 70–80 µm); inferior volsella slender (200 µm long, 20 µm wide) with a long digitiform projection, directed caudally................................................... D. zernyi

- Gonocoxite shorter and wider (300–400 µm, breadth 160–180 µm); inferior volsella stouter (200 µm long, 60–70 µm wide), digitiform projection of inferior volsella short...................................................... D. vaillanti

6 Inferior volsella simple appearing as a large flap; gonostylus with the slender distal part longer than the proximal bulbous part........................................................................................... D. cinerella

- Inferior volsella double with lobes of different length, the lateral one longer; gonostylus with the slender distal part as long as the bulbous proximal part........................................................................ D. tonsa

7 Gonostylus very long, about 0.7 times length of gonocoxite; inferior volsella long, slender, with 1–3 long medially directed setae at about 0.5 its length and about 3 long setae at its distal end.................................... D. insignipes

- Gonostylus short, less than 0.7 times the length of gonocoxite; inferior volsella short, expanded medially, with many strong setae ventro-medially................................................................... bertrami group ... 8

8 Anal point present, but short, with rounded apex, not projecting beyond T IX; inferior volsella adhering to gonocoxite without robust setae; aedeagal lobes large triangular, with a characteristic point in postero-lateral position; two robust setae on the postero-medial corner of gonocoxite............................................................. D. nowickiana

- Anal point very long, well projecting beyond T IX; inferior volsella not adhering to gonocoxite, with strong setae directed medially; aedeagal lobes without a characteristic point in postero-lateral position; no robust setae on postero-medial corner of gonocoxite..................................................................................... D. bertrami

9 Inferior volsella present, but not well separated from gonocoxite.............................................. 16

- Gonocoxite with a well separated inferior volsella......................................................... 10

10 Sternapodeme with a pointed median part; inferior volsella divided in two lobes, but only medial lobe well separated from gonocoxite; gonocoxite without two robust setae in its distal part........................................ D. martae

- Sternapodeme arched; inferior volsella divided into two or three parts, all well separated from gonocoxite; gonocoxite with two robust setae in its distal part........................................................... latitarsis group 11

11 Gonostylus without a strong median expansion; anal point long and slender; pars ventralis digitiform, elongated........ 12

- Gonostylus with a median expansion; anal point short and large; pars ventralis very large.................. D. laticauda

12 Inferior volsella with a small, dorso-lateral flat or finger-like projection and two stronger, ventro-medial spine- and seta-bearing projections..................................................................................... 13

- Inferior volsella with dorso-lateral lobe very reduced or elongated, but never digitiform or flat, ventro-medial lobe without spine or seta bearing projections........................................................................ 14

13 Dorso-lateral lobe of inferior volsella finger-like short but well visible.................................. D. lindrothi

- Dorso-lateral lobe of inferior volsella, large flat................................................ D. goetghebueri

14 Dorso-lateral lobe very small difficult to see; ventro-medial lobe of inferior volsella very developed, elongated, bearing spoonlike supple setae............................................................................. D. wuelkeri

- Dorso-lateral lobe of inferior volsella well developed, longer than the ventro-medial lobe.......................... 15

15 Dorso-lateral and ventro-medial lobes of inferior volsella well separated to each other; dorso-lateral lobe more elongated, slen- der........................................................................................ D. latitarsis

- Dorso-lateral and ventro-medial lobes of inferior volsella almost fused; dorso-lateral lobe less elongated, only a little longer than ventro-medial lobe, wider................................................................... D. modesta

16 Anal point absent; pars ventralis short, T IX very weak medially, appearing to be formed of two separate sclerites; inferior volsella flat, densely covered of setae, barely protruding from gonocoxite.................................. D. incallida

- Anal point present; pars ventralis and T IX well developed; inferior volsella never protruding from gonocoxite.......... 17

17 Eyes apparently bare, but with very short pubescence visible at large magnification; inferior volsella present, with slightly expanded distal end and moderately long setae; anal point short, shorter than the length of T IX; aedeagal lobes normal; tarsomeres cordiform; gonocoxite without lobes; gonostylus fairly slender, straight, of nearly equal width throughout.. D. aberrata

- Eyes completely devoid of microtrichia; inferior volsella very weakly differentiated, without sharp dorsal margin and without expanded distal end; anal point needle-like, not quite or just reaching distal ends of aedeagal lobes; aedeagal lobes very sclerotized, dark; tarsomeres cylindrical; gonocoxite with a small lobe in caudal position, gonostylus fairly sharply narrowed basally.................................................................................................. 18

18 Aedeagal lobes, with 4-5 fine apical denticles; anal point larger, at least 10 µm wide, with two small apical spines; gonostylus without an enlargement in the middle............................................................ D. permacra

- Aedeagal lobes, with two large apical spines; anal point less than 10 µm wide, with only one apical spine; gonostylus with an

enlargement in the middle....................................................................... D. dampfi 19 Anal point short, weak, directed ventrally; phallapodeme short, narrow, appearing as a lateral projection of aedeagal lobe; inferior volsella weak, only outlined without free distal end; gonostylus triangular.................................... 20

- Anal point very long, basal part sclerotized, distal part not sclerotized; phallapodeme wide, robust; inferior volsella beak-like, with a group of long setae ventrally; gonostylus almost squared........................................ D. longipes

20 Anal point short and slender (75–120 µm); inferior volsella visible only as a small appendage; total body length 2.0– 3.5 mm ......................................................................................... D. steinboecki

- Anal point short, triangular; gonocoxite without visible inferior volsella; total body length 3.2–3.4 mm ......................................................... D. starmachi (known only as larvae and pupal exuviae from the Italian Alps)