Descriptions of the last instar larvae of two species of Megalestes Selys from Yunnan, China (Odonata: Zygoptera: Synlestidae)

The ﬁnal stadium larvae of Megalestes micans Needham,


Materials and methods
During fieldwork in Mt. Jizushan, Binchuan Town, Yunnan Province, China conducted in June 2019, the larvae of M. kurahashii and M. micans were found in a small pond full of fallen leaves. The larvae were collected using a dip net, and were reared in a laboratory in plastic containers. All the in vivo pictures were taken in the field and laboratory, with a digital camera (Nikon D7200, Thailand), measured, and characters photographed in the laboratory using the Keyence VHX-5000 (made in Japan) digital microphotography system. All species identifications were confirmed by the adults that emerged. Mandibular terminology and formulae follow Watson (1956), and S means abdominal segment(s). *Corresponding author. Email: yanggh727@sina.com  Needham, 1930 ( Figures 1, 2 Head. Wider than long, about 1.4 times as long as length. Occipital margin concave. Labrum smooth, light brown, its edge dark, surface smooth. Compound eyes black and prominent. Antenna filiform in shape, 7-segmented, the third is the longest. Length of each antennal segment (mm): 0.70, 1.9, 2.1, 1.2, 1.3, 0.6, 0.5 ( Figure 2a). Prementum 1.7 × longer than wide, without mental and lateral setae (Figure 2b, c). Median lobe with uniform marginal denticles; median cleft shallow. Labial palp slender, with two end hooks of unequal size, the inner one longer and larger than the outer; movable hook long and acuminate, curved inward medially (Figure 2b Thorax. Light brown, smooth, with irregular black marks. Prothorax rectangular. Synthorax trapezoidal, elongate. Legs long and slender, marked with yellow bands each on distal end of femur and tibia (Figure 1). Wing cases parallel, forewing cases reaching to hind border of S3, hind wing extending to middle of S4 (Figure 2m).

Megalestes micans
Abdomen. Slender and cylindrical, brown or yellowish brown dorsally with paired blackish brown stripes and dots on each segment; S10 keeled dorsally, bearing numerous small spines dorsally and ventrally; lateral spines small, present on S5-9. Caudal gills (both lateral gills and median gill) leaf shaped, with black mid-ribs and numerous black spots (Figure 2k-m), the markings are more obvious in living larvae (Figure 6a, b). The ovipositor of female long, reaching end of S10 (Figures 2n, 3a).

Head. Mouthparts very similar to M. micans
Thorax. Very similar to M. micans but hind wing cases extending to basal 1/3 of S4 (Figure 5j).
Abdomen. Dark brown dorsally, with paired blackish brown stripes and dots on each segment. Lateral spines small, present on S6-9. Ovipositor of female extending to basal 2/3 of S10 (Figures 3b, 5i). Caudal gills (both lateral gills and median gill) almost black, with light brown spots (stripes) as follows: four small irregular light brown spots at the base and middle, a large light stripe apically (Figure 5h, j).

Differential diagnosis
The larvae of M. kurahashii can be easily separated from that of M. micans by caudal gill color and length of female ovipositor (caudal gills almost black and female ovipositor extending to basal 2/3 of S10 in M. kurahashii, but caudal gills with black stripes and female ovipositor reaching end of S10 in M. micans) (Figures 3, 6a).
Of the seven known larvae of Megalestes species, the larvae of both M. kurahshii and M. micans have black streaked caudal gills, easily distinguishing them from other known Megalestes larvae (Table 1).
A key to the larvae of seven species of the genus Megalestes