Idionyx Hagen, 1867

Subramanian, K. A., Rangnekar, Parag & Naik, Rohan, 2013, Idionyx (Odonata: Corduliidae) of the Western Ghats with a description of a new species, Zootaxa 3652 (2), pp. 277-288 : 283-285

Key to Idionyx Hagen, 1867 of the Western Ghats (modified after Fraser 1936)

Idionyx of the Western Ghats are differentiated from the other species of the genus in the Indian subcontinent by the absence of a yellow humeral stripe on the thorax in both males and females except in the case of female I. nadganiensis . A comparison of morphological features of the Western Ghats species is provided in Table 2 .

Males:

1. Labrum black.................................................................................. I. minima

Labrum bright yellow with narrow black border............................................................. 2

2. Cerci with row of teeth beneath basal half.................................................................. 3

Cerci without row of teeth beneath basal half............................................................... 7

3. Epiproct shorter than cerci.............................................................................. 4

Epiproct longer than cerci.............................................................................. 6

4. Apical portion of epiproct broad and shallowly emarginated, directed straight back in line with basal portion.... I. saffronata

Apical portion of epiproct very narrowly and deeply emarginated............................................... 5

5. Apical portion of epiproct sloping strongly up at an angle to basal portion.................................. I. galeata

Apical portion of epiproct directed straight back in line with basal portion............................ I. travancorensis

6. Anal appendages long and slender. Cerci straight and epiproct arched downwards in lateral profile. Lateral lobes of epiproct with tuft of golden hairs at apex I. gomantakensis

Anal appendages thick and curving inward in lateral profile................................................... 7

7. Lateral lobes of epiproct as upward angulations of lateral border.......................................... I. corona

Lateral lobes of epiproct as tiny thin erect spines........................................... I. corona burliyarensis

Females:

1. Humeral thoracic stripe present................................................................ I. nadganiensis

Humeral thoracic stripe absent........................................................................... 2

2. Labrum black.................................................................................. I. minima

Labrum mostly reddish brown or yellow................................................................... 3

3. Labrum reddish brown with two very large diffuse yellow spots at centre............................... I. periyashola

Labrum yellow narrowly bordered with black or brown...................................................... 4

4. Vesicle swollen, rounded at apex............................................................... I. nilgiriensis

Vesicle either markedly produced or simple with rounded or conical apex......................................... 5

5. Vesicle markedly produced............................................................................. 6

Vesicle simple, with rounded or conical apex............................................................... 7

6. Vesicle a short blunt horn.................................................................. I. travancorensis

Vesicle a short cone with a sinuous spine extending back from apex............................... I. c. corona Fraser

Vesicle an elongate, bluntly pointed curved cone............................................ I. corona burliyarensis

Vesicle a short cone with a long, simple, straight spine extending back from apex....................... I. rhinoceroides

Vesicle a short cone surmounted by an obtuse tubercle with a tent-shaped spine extending back from apex........ I. galeata

7. Vesicle rounded above, frons deeply grooved...................................................... I. saffronata

Vesicle conical above, frons shallowly grooved................................................ I. gomantakensis

Geographic distribution. The genus Idionyx is recorded between 8 0 N and 16 0 N in the Western Ghats ( Map 1 ), where it is restricted to wet southern and western slopes. Fraser (1936) mentions that the genus was never observed below 2000 ft (600 m) in the Western Ghats. However, in recent field studies adults were recorded as low as 13 m on the west coast. Details of geographic distribution of species are provided in Table 3 . High diversity of this genus is reported from Niligiri, Wyanad and Coorg districts, between 10 0 N and 12 0 N.

Habitat and ecology. In the Western Ghats, the genus is restricted to evergreen forests, especially in riparian zones ( Figure 1 ). The species of this genus fly erratically close to the ground in closed canopy forests. The active flight period of the genus in the Western Ghats is between April and September. Females of I. corona burliyarensis have been observed laying eggs in hill streams communally. Adults were sometimes recorded away from typical habitat in forest plantations, semiurban and urban areas. The distribution of species across altitude, temperature and rainfall in the Western Ghats is provided in Table 4 .

Figures

MAP 1. Distribution of Idionyx in the Western Ghats. Inset shows the location of the Western Ghats in the Indian subcontinent.

FIGURE 1. Typical habitat of Idionyx in the Western Ghats.