Morphological variation in invasive mosquito Culex quinquefasciatus Say (Diptera: Culicidae) larvae from an urban site in Auckland, New Zealand

Figures & data

Table 1. The nine diagnostic characters used to identify Culex quinquefasciatus larvae, based on Snell (2005) and Belkin (1962, 1968). In addition, a Culex pervigilans mantle plate character is also given for comparative purposes.

Characters	Expected
1) Number of siphonal ventro-lateral hair tufts	4 pairs of ventro-lateral hair tufts (Figure 2A)
2) Siphon hair tuft alignment	Seta 1d-S not aligned (Figure 2A)
3) Number of pecten teeth	8–12 pecten teeth (Figure 2B)
4) Seta 1a-S position in relation to the pecten teeth	Seta 1a-S usually above level of pecten teeth (Figure 2B)
5) Siphon shape	Distinct bulge in lower half to middle (Figure 2C)
6) Lateral comb patch	30–40 lateral comb hairs (Figure 2D)
7) Length of anal papillae in relation to the saddle	Papillae about length of the saddle (Figure 2E)
8) Length of dorsal anal papillae in relation to ventral anal papillae	Dorsal anal papillae longer than ventral anal papillae (Figure 2E)
9) Number of mantle plate teeth	9–11 mantle teeth on each side of the median apical tooth (Figure 2F,G)
10) Number of mantle plate teeth in Culex pervigilans	6–9 mantle teeth on each side of the median apical tooth (Figure 2H)

Figure 1. Main body parts of a Culex quinquefasciatus larva.

Figure 2. Standard morphological characters used to identify Culex quinquefasciatus larvae. A, Four pairs of ventro-lateral hair tufts, and seta 1d-S not aligned (this image is of a < 3rd instar larvae); B, the pecten teeth, and seta 1a-S positioned above the pecten teeth; C, distinct siphon bulge; D, lateral comb hairs; E, anal papillae about length of the saddle. and dorsal anal papillae longer than ventral anal papillae; F, mantle plate; G, mantle plate drawing modified from Belkin (1962); H, Culex pervigilans mantle plate drawing modified from Belkin (1962).

Figure 3. Some morphological variations observed in Culex quinquefasciatus larvae. A, Seta 1a-S in line with pecten teeth rather than above; B, seta 1a-S positioned below the level of pecten teeth rather than above; C, slight bulge of siphon, rather than distinct bulge; and D, anal papillae longer than saddle rather than equal.

Figure 4. Culex quinquefasciatus larvae displaying seta 1c-S out of alignment, instead of seta 1d-S.

Table

Character 8:	Length of dorsal anal papillae in relation to length of ventral anal papillae (< 3rd instars: 93.6%; 3rd/4th instars: 96.7%) (Figure 2E)
Character 9:	Number of mantle plate teeth (< 3rd instars: 91.5%; 3rd/4th instars: 94.2%) (Figure 2F,G).
Character 3:	Number of pecten teeth (< 3rd instars: 91.3%; 3rd/4th instars: 94.0%) (Figure 2B).

Figure 5. The nine diagnostic characters used for identification of Culex quinquefasciatus and their observed frequency (presence) in < 3rd instar (n = 149) and 3rd/4th instar larvae (n = 414) collected at the Auckland Zoo.

Table

Character 9:	The mantle plate; not visible in 20.8% of < 3rd instar larvae and 21.3% of 3rd/4th instar larvae due to either the dark colouration of some larger specimens (possibly about to enter the pupal stage) or tissue content in the head blocking the view of the structure.
Character 8:	Length of dorsal anal papillae in relation to ventral anal papillae; the anal papillae were missing in 6% of < 3rd instar larvae and 3.9% of 3rd/4th instar larvae.
Character 7:	Length of anal papillae in relation to the saddle; the anal papillae were missing in 6% of < 3rd instar larvae and 3.9% of 3rd/4th instar larvae.

Table 2. Co-occurrence of the nine main diagnostic features used in the identification of Culex quinquefasciatus 3rd and 4th instar larvae.

Coincidental features	8–12 pecten teeth	Mantle plate teeth 9–11	Siphon bulge	Anal papilla about length of saddle	4 pairs of siphonal V/L tuffs	Lateral comb patch (30–40 hairs)	Siphon seta 1d-S not aligned	Seta 1a-S usually above level of pecten teeth
Dorsal papilla longer than ventral	362/398 (91%)	281/310 (90.6%)	289/398 (72.6%)	283/398 (71.1%)	275/398 (69.1%)	266/398 (66.8%)	148/398 (37.2%)	36/398 (8.7%)
8–12 pecten teeth		293/326 (89.9%)	301/414 (72.7%)	279/414 (70.1%)	277/398 (66.9%)	267/414 (64.5%)	152/414 (36.7%)	39/414 (9.4%)
Mantle plate 9–11			242/326 (74.2%)	214/310 (69%)	216/326 (66.3%)	213/326 (65.3%)	121/326 (37.1%)	27/326 (8.3%)
Siphon bulge				232/398 (58.3%)	227/414 (54.8%)	213/414 (51.4%)	135/414 (32.6%)	25/414 (6%)
Anal papilla about length of saddle					206/398 (51.8%)	199/398 (50%)	115/398 (28.9%)	24/398 (6%)
4 pairs of siphonal V/L tuffs						207/414 (50%)	150/414 (36.2%)	22/414 (5.3%)
Lateral comb patch (30–40 hairs)							113/414 (27.3%)	25/414 (6.3%)
Siphon seta 1d-S not aligned								7/414 (1.7%)

Snell AE. 2005. Identification keys to larval and adult female mosquitoes (Diptera: Culicidae) of New Zealand. New Zealand Journal of Zoology. 32(2):99–110. doi: 10.1080/03014223.2005.9518401

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