Plasticity of mate-guarding and oviposition behaviour in Zygonyx natalensis (Martin) (Anisoptera: Libellulidae)
Odonatologica , Volume 20 - Issue 3 p. 293- 302
The African dragonfly, Z. natalensis. inhabits waterfalls and rapids. For oviposition at rocky river courses, current-washed mats of plant roots are of great importance. Because of strongly varying water levels and currents the oviposition sites are limited and their suitability is unpredictable. — Males hover over rapids, where the females appear. After copulation on the wing the pairs look for an oviposition site in tandem. As a rule, they separate for oviposition. Guarded by the male, the female settles on roots or stalks and allows the discharged eggs to be washed away by the current. The eggs are covered by a gelatinous secretion which expands rapidly in contact with water and causes the eggs to stick to the soil or roots. Apart from this, there are other types of oviposition: the female may stick her eggs directly to the substrate through movements of the abdomen whilst in a sitting position, or position the eggs in the main current while dipping in flight. If the searching tandem is disturbed, it frequently flies away. Disturbed tandems still manage to oviposit. In this case the male often stays in contact. Oviposition in tandem occurs only in flight and is less successful than the other 3 types. — The plasticity of oviposition behaviour is an adaptation to the high intraspecific competition between males and to the limitation and unpredictability of suitable oviposition sites. Oviposition in tandem occurs only when the risk of take-over by another male is great.
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