Can you believe that this hit the national news. Dragonfly females make out that they are dead to avoid sex. So what’s new? Why is this news. Let’s get back to basics. When mammals want to make babies they have to go through all that tiresome business of sex; indeed some mammals (Lions) have to do every 15 minutes or it won’t work. Many insects on the other hand (dragonflies included) only need to have sex once as the females can store the male’s sperm. In addition, sex can be a very time consuming process; If you live for only 4 weeks and sex takes up to 24 hours as it does in some damselflies, it’s a huge portion of your life that you should be spending laying eggs. It is easy to see how females, once mated, try to avoid sex. As for feigning death, I have witnessed this in the Pseudostigmatidae, which are huge helicopter damselflies found in South America. They are far too slow and cumbersome to fly away from predators so at the sign of danger they simply shut their wings and fall to the ground. I remember my friend Pete spending the whole of an afternoon in Brazil looking for a fallen insect. It was so well camouflaged he never found it. Avoiding predators certainly but avoiding sex? Hawker dragonflies (Aeshnidae) provide the best examples. Some species lay in tandem (see picture of Anax ephippiger in earlier blog) but where the females lay alone they need to adopt avoiding techniques. Boyeria irene, one of Europe’s commonest hawkers, breeds along shady banks of streams and rivers. The females usually appear late in the day when most males have left.They work their way amongst the tree roots to lay but if a male comes by they freeze. They stop rustling their wings and are completely motionless until the danger passes. Aeshna juncea adopts a similar technique freezing and flattening its body against the ground until the male moves away. Of course it doesn’t always work. I remember seeing a male spot a female ovipositing. She tried to fly off but the male literally knocked her to the ground, coupled with the stunned female, who copulated as she recovered.
Moving on to the darters and clubtails (Libellulidae and Gomphidae) they do not have ovipositors so simply distribute their eggs over the surface of the water. The females cannot hide but I think the boot is on the other foot. Copulation is fairly rapid and the females appear to relish the attention. I remember observing Orthetrum cancellatum on a lake in Dorset and Crocothemis erythraea on a river in Spain. The females were having a.ball. A few seconds of oviposition followed by some quickie sex then back to the egglaying. What a life.
A cannot leave this subject without mention of the genus Ischnura. These are small damselflies which, almost uniquely amongst Zygoptera, oviposit alone. More importantly the females are dominant and whilst ovipositing woebetide any male that comes near, they are abruptly chased off. Indeed there is one species Ischura hastata which is a common American species. It has a colony in the Azores where no male insects have ever been found; the females lay viable unfertilised eggs. Perhaps Ischnura has provided the ultimate solution to male harassment; no need to feign death, eliminate sex altogether.
We know about the colony in the Azores. Do other species of Ischnura operate with out males?
Moving on to the darters and clubtails (Libellulidae and Gomphidae) they do not have ovipositors so simply distribute their eggs over the surface of the water. The females cannot hide but I think the boot is on the other foot. Copulation is fairly rapid and the females appear to relish the attention. I remember observing Orthetrum cancellatum on a lake in Dorset and Crocothemis erythraea on a river in Spain. The females were having a.ball. A few seconds of oviposition followed by some quickie sex then back to the egglaying. What a life.
A cannot leave this subject without mention of the genus Ischnura. These are small damselflies which, almost uniquely amongst Zygoptera, oviposit alone. More importantly the females are dominant and whilst ovipositing woebetide any male that comes near, they are abruptly chased off. Indeed there is one species Ischura hastata which is a common American species. It has a colony in the Azores where no male insects have ever been found; the females lay viable unfertilised eggs. Perhaps Ischnura has provided the ultimate solution to male harassment; no need to feign death, eliminate sex altogether.
We know about the colony in the Azores. Do other species of Ischnura operate with out males?
RSS Feed