Culex

Azari-Hamidian, Shahyad & Harbach, Ralf E., 2009, Keys to the adult females and fourth-instar larvae of the mosquitoes of Iran (Diptera: Culicidae), Zootaxa 2078, pp. 1-33 : 21-23

Key to subgenera and species of genus Culex : fourth-instar larvae

(key characters are illustrated in Figs 5 and 6 )

1. Seta 4-X (ventral brush) with 1 or more precratal setae; thorax and abdomen spiculate [siphonal trachea narrow, less than 0.5 width of siphon] .................................................................................................................................. 2

- Seta 4-X without precratal setae; thorax and abdomen not spiculate, except Cx. (Cux.) vishnui (with thorax spiculate) ........................................................................................................................................................................... 6

2(1). Seta 3-P more than 0.5 length of setae 1,2-P; siphon with 2 or more (usually more) anterolateral setae on each side; seta 1-S (siphonal tufts) unpaired, occurring in single median posterior row; seta 2-S (apicodorsal seta of siphon) large and hooked; siphon not expanded at apex; seta 6-C (median frontal seta) with at least 2 branches; seta 1-C (preclypeal seta) pale, more or less stout, never strongly tapered or filamentous (subgenus Maillotia ) ... 3

- Seta 3-P about 0.5 or less length of setae 1,2-P; siphon without anterolateral setae; seta 1-S more or less paired, occurring in 2 posterolateral rows; seta 2-S small and straight, not hooked; siphon slightly expanded at apex; seta 6-C single; seta 1-C dark, otherwise same as above (subgenus Neoculex ) ............................................................. 5

3(2). Siphon with numerous strong setae on subdorsal part of distal 0.67; siphon index (SI) less than 5.0 (4.4); seta 1-S (siphonal tuft) inserted beyond pecten [PTF 3–4:1:2:3:1:1:3] .............................................................. Cx. arbieeni

- Siphon without such setae; SI more than 5.0; usually at least 1 pair of seta 1-S (siphonal tufts) inserted within pecten........................................................................................................................................................................ 4

4(3). Seta 3-P (prothoracic seta 3) bifid; seta 8-P (prothoracic seta 8) usually single; seta 1-S (siphonal tuft) often less than 0.3 length of siphon; anal papillae (gills) longer than saddle; siphon more than 4.0 length of saddle; siphon index (SI) 6.5 or greater (6.5–8.0) [PTF 1:1:2–3:4:1:1:3] ................................................................... Cx. hortensis

- Seta 3-P single; seta 8-P usually with 2 or 3 branches; seta 1-S often more than 0.3 length of siphon; anal papillae shorter than saddle; siphon less than 4.0 length of saddle; SI less than 6.5 (6.0–6.4) [PTF 1:1:1:3:1:1:4] ............... ........................................................................................................................................................... Cx. deserticola

5(2). Length of seta 1-S (siphonal tuft) usually more than 2.0 (1.5–3.0) width of siphon at point of attachment; more distal pecten spines evenly spaced, each with 3 long ventral denticles; anal papillae (gills) about 0.5 length of saddle, blunt tipped [SI 6.1–8.5; PTF 1:1:3:2:1:1:3] ............................................................ Cx. impudicus * (Note 33)

- Seta 1-S at most 2.0 (usually less than 1.5) width of siphon at point of attachment; more distal pecten spines often more widely spaced and somewhat irregularly inserted, each with 1 or 2 ventral denticles; anal papillae nearly as long or longer than saddle, pointed [SI 6.0–7.0; PTF 1:1:3:2:1:1:3] .................................................... Cx. territans

6(1). Seta 1-S (siphonal tufts) in single row, with all elements arranged in more or less straight line; seta 3-C absent [siphonal trachea broad, more than 0.5 width of siphon; at least one pair of seta 1-S inserted within pecten; seta 1- C (preclypeal seta) pale, very slender and distally strongly tapered or filamentous] (subgenus Barraudius )......... 7

- Seta 1-S in 1 or 2 rows, with 1-3 elements distinctly out of line with the others (inserted laterally); seta 3-C usually present (may be absent in some species, such as Cx. (Cux.) pipiens and Cx. (Cux.) vishnui ) .......................... 8

7(6). Siphon index (SI) about 3.0 (2.6–3.2); pecten at least 0.5 length of siphon; 2 apical seta 1-S (siphonal tufts) at least as long as width of siphon at point of attachment; 2 pairs of seta 1-S inserted within pecten; anal papillae (gills) about 0.5 length of saddle, scarcely longer than diameter, dorsal pair slightly longer than ventral pair; seta 8-P (prothoracic seta 8) usually single [PTF 1:1:1:2:1:1:3] ................................................................... Cx. pusillus

- SI about 4.0 or more (3.8–5.0); pecten less than 0.5 length of siphon; 2 apical seta 1-S shorter than width of siphon at point of attachment; 1 pair of seta 1-S inserted within pecten; anal papillae slightly shorter than saddle, slender and tapering, same length; seta 8-P with 2 or 3 branches [PTF 1:1:1:1–2:1:1:3].................... Cx. modestus

8(6). Dorsomentum of head a straight-sided triangle with minutely serrate margins; pecten very short, with 7–9 spines grouped at base of siphon, less than 0.1 length of siphon; seta 1-A (antennal tuft) inserted near mid-length of antenna; median labral plate (preclypeus or labrum) indistinguishably fused to dorsal apotome (frontoclypeus) [comb with 4–8 large scales, each with distinct main spine; distal pecten spines with 7 or more ventral denticles; seta 1-C (preclypeal seta) stout, distinctly thicker than branches of setae 5,6-C; SI 6.8 (5.0–8.4); PTF 1:1:1:1–2:1:1:3] (subgenus Oculeomyia ) (Note 32)................................................................ Cx. bitaeniorhynchus

- Dorsomentum an imperfect triangle with large teeth; pecten much longer, about 0.33 length of siphon; seta 1-A inserted near apex of antenna; median labral plate distinct, separated by suture from dorsal apotome (subgenus Culex ) ..................................................................................................................................................................... 9

9(8). Some or all comb scales spiniform, with pointed apex and fringe at sides ........................................................... 10

- All comb scales evenly fringed at sides and apex .................................................................................................. 14

10(9). Comb with fewer than 25 spiniform scales (usually fewer than 20), each with distinct main spine [seta 1-C (preclypeal seta) pigmented, stout, distinctly thicker than branches of setae 5,6-C] (Note 33) .................................. 11

- Comb with more than 25 spiniform scales, without distinct main spine................................................................ 12

11(10).Comb with 4–8 (rarely up to 19) large spiniform scales in single row; thorax not spiculate; seta 1-S (siphonal tufts) with 5 or fewer branches; distal pecten spines with 7 or more ventral denticles of similar size arising along entire length [SI 5.4 (4.4–6.9); PTF 1:1:1:1–3:1:1:3] ................................................................. Cx. pseudovishnui

- Comb with 16–22 small spiniform scales in 3 or 4 rows; thorax spiculate; seta 1-S with 6 or more branches; distal pecten spines with 2–5 ventral denticles of different size arising proximally [PTF 1:1:1:2:1:1:3] .... Cx. vishnui *

12(10).Seta 2-S long and curved; antenna with setae 2,3-A (subapical setae) arising at 0.3–0.5 distance between apical setae and seta 1-A (antennal tuft); seta 7-I about as long as 6-I, usually single; seta 14-C single; distal pecten spines with 7 or more ventral denticles; seta 1-C (preclypeal seta) stout, distinctly thicker than branches of setae 5,6-C (inner and median frontal setae), dark [siphonal trachea narrow, less than 0.5 width of siphon; SI 6.0 (4.5–7.4); PTF 1:1:1:1:1:1:2–3] ....................................................................................................... Cx. mimeticus

- Seta 2-S always straight; setae 2,3-A arising adjacent to apical setae; seta 7-I distinctly shorter than 6-I, usually double; seta 14-C with 2 or more branches, rarely single; distal pecten spines with 2–5 ventral denticles of different size arising proximally; seta 1-C slender, usually not thicker than branches of setae 5,6-C, dark or pale....... 13

13(12).Siphon with all elements of seta 1-S (siphonal tufts) arising laterally and posterolaterally, with 1–4 branches; siphonal trachea narrow, less than 0.5 width of siphon; pecten spines not large and curved; some anterior scales of comb evenly fringed at sides and apex; seta 5-C (inner frontal seta) with 1 or 2 branches (usually single), shorter than seta 6-C (median frontal seta); seta 14-P double on at least one side; siphon index (SI) more than 5.5 (6.9; 5.9–8.1); seta 1-C (preclypeal seta) pale, very slender and strongly tapered or filamentous [PTF 1:1:1:1–4:1:1:3]. ............................................................................................................................................................. Cx. sinaiticus

- Siphon with most elements of seta 1-S arising relatively close to posterior midline, with 4–11 branches; siphonal trachea broad, more than 0.5 width of siphon; more distal pecten spines very large and curved; all scales of comb spiniform; seta 5-C with 3 or 4 branches, about as long as seta 6-C; seta 14-P single; SI less than 5.5 (4.7; 4.1–5.4); seta 1-C dark, more or less stout, never strongly tapered or filamentous [PTF 1:1:1:2:1:1:3–4]............... ................................................................................................................................................................ Cx. theileri

14(9). Distal pecten spines with 7 or more ventral denticles of similar size arising along entire length; seta 1-C (preclypeal seta) dark, stout, spiniform or foliform, abruptly pointed or blunt apically, distinctly thicker than branches of setae 5,6-C (inner and median frontal setae) ......................................................................................................... 15

- Distal pecten spines with 2–5 ventral denticles of different size arising proximally; seta 1-C usually pale or pigmented, never dark, slender, scarcely if at all thicker than branches of setae 5,6-C ............................................. 16

15(14).Seta 1-S (siphonal tufts) mostly inserted in irregular row on posterior margin of siphon; anal papillae (gills) very small and globular, about 0.5 length of saddle or less; siphon index (SI) less than 5.0 (3.8, 3.6–4.6); seta 5-C (inner frontal seta) with at least 6 (6–8) branches; seta 6-C (median frontal seta) with at least 4 (4–7) branches; seta 1-X (saddle seta) usually single; seta 1-C (preclypeal seta) markedly flattened, or somewhat foliform, with blunt apex [PTF 1:1:1:2:1:1:2–3] ............................................................................................................. Cx. sitiens

- Seta 1-S in posterolateral pairs; anal papillae elongate, never globular; SI more than 5.0 (6.3, 5.7–7.0); seta 5-C with 4 or fewer branches; seta 6-C with 3 or fewer branches; seta 1-X usually triple (2–4); seta 1-C slender and spiniform, with acuminate apex [PTF 1:1:1:1–2:1:1:2–3] ..................................................... Cx. tritaeniorhynchus

16(14).Siphon with 6–8 pairs of seta 1-S (siphonal tufts), with one pair arising laterally and 5–7 irregular pairs arising relatively close to posterior midline; seta 1-S with 2 pairs arising within pecten [seta 1-C (preclypeal seta) pale, more or less stout, never strongly tapered or filamentous; SI 3.5 (2.8–4.6); PTF 1:1:1:2:1:1:3–4] ... Cx. laticinctus

- Siphon with 3–6 pairs of seta 1-S, with 1-3 pairs arising laterally and 2–4 pairs arising posterolaterally; seta 1-S at most with 1 pair arising within pecten ................................................................................................................... 17

17(16).Seta 1-S (siphonal tufts) no longer than width of siphon at point of attachment, usually in 5 pairs; all seta 1-S subequal in length; seta 6-VI normally single; seta 5-C (inner frontal seta) usually double or triple (occasionally with 4 branches); seta 6-C (median frontal seta) at most with 3 (2 or 3) branches; seta 1-C (preclypeal seta) more or less stout, never strongly tapered or filamentous ................................................................................................... 18

- Seta 1-S longer than width of siphon at point of attachment, usually in 4 pairs; at least basal 2 pairs of seta 1-S distinctly longer than apical setae; seta 6-VI normally double; seta 5-C with 4 or 5 branches; seta 6-C usually with more than 3 branches; seta 1-C pale, very slender and distally strongly tapered or filamentous ......................... 20

18(17).Siphon with 3 lateral pairs of seta 1-S (siphonal tufts); seta 1-M usually double or triple, sometimes single; seta 5- C (inner frontal seta) usually with 2 branches; distal pecten spines usually with 2 ventral denticles; seta 1-C (preclypeal seta) long, thin and pale [SI 6.8 (5.4–8.2); PTF 1:1:1:2:1:1:3]............................................ Cx. antennatus

- Siphon with 2 lateral pairs of seta 1-S (siphonal tuft); seta 1-M usually single, sometimes double; seta 5-C usually with 3 branches; distal pecten spines usually with 3 or more ventral denticles; seta 1-C not as long, slightly stouter and pigmented ....................................................................................................................................................... 19

19(18).Seta 1-S (siphonal tufts) as long as width of siphon at point of attachment [SI 6.8 (5.4–7.9); PTF 1:1:1:2:1:1:3–4] Cx. perexiguus

- Seta 1-S distinctly shorter than width of siphon at point of attachment [SI 5.7 (4.9–7.2); PTF 1:1:1:2:1:1:2–3] ..... ........................................................................................................................................ Cx. univittatus * (Note 37)

20(17).Seta 1-III–V with 3–6 branches (usually 4 or 5), sum of their branches on one side of abdomen 10 or more (usually more); seta 1-M normally double or triple; seta 1-X (saddle seta) usually double [SI 5.2 (4.4–5.7); PTF 1:1:1:2:1:1:2–3] ............................................................................................................... Cx. torrentium (Note 38)

- Seta 1-III–V with 1–4 branches (usually 1 or 2), sum of their branches on one side of abdomen not exceeding 10 (usually 6 or fewer); seta 1-M normally single; seta 1-X usually single............................................................... 21

21(20).Integument of thorax and abdomen with rows of minute vesicles; seta 13-T as long as 12-T; seta 1-C (preclypeal seta) pigmented, usually spiculate in middle [SI 5.4 (3.9–6.7); 1:1:1:2:1:1:2–4] ................ Cx. vagans * (Note 36)

- Integument of thorax and abdomen without vesicles; seta 13-T distinctly shorter than 12-T; seta 1-C usually not pigmented, sides smooth ........................................................................................................................................ 22

22(21).Siphon usually widest in middle, tapering more strongly apically than basally; width of siphon at apex more than 0.5 width at base; siphon index (SI) never more than 4.6 usually about 4.0 (3.7; 2.8–4.6); siphonal saddle index less than 3.45; seta 1-III, IV usually single [PTF 1:1:1:2:1:1:2] ............................................ Cx. quinquefasciatus

- Siphon widest at base, tapering towards apex, slightly sigmoid in lateral view; SI usually about 5.0 (4.6; 3.0–5.8); siphonal saddle index greater than 3.45; seta 1-III, IV usually double [PTF 1:1:1:2–3:1:1:2–3].............................. ..................................................................................................................... Cx. pipiens (including form molestus)

Figures

FIGURE 5. Characters of the head of mosquito larvae used in the keys. Dorsal and ventral aspects of a culicine larva. (Modified from Harbach & Knight, 1980).

FIGURE 6. Characters of mosquito larvae used in the keys. A, Lateral aspect (right side) of an aedine larva. B, C, Lateral aspects (left sides) of the terminal abdominal segments of a Culiseta and an Anopheles larva, respectively. (Modified from Harbach & Knight, 1980).