‘Love’ is in the air…
Summer rules these days in Hong Kong, humid and hot it is.
Living in a green quiet area near some nice falls is a real treat, not only for the refreshment of the pools but it is also a perfect spot to observe some amazing insects during this time of the year.
With dazzling names as Golden Flangetail, Emerald Cascaders, Ruby Darters you can guess we are not talking about some dull looking creatures here but dragonflies!
Unless you’re an entomologist,if somebody asked you to list the insects you like most, the answer is always the same: butterflies, dragonflies, and ladybugs, colourful and harmless.Is that really the case? Dragonflies are some of the most brutal killers in the insect world.They deserve their mythical ‘dragon’names!
Dragonflies belong to the order of insects known as Odonota, in Greek, that means “toothed ones,” which is fitting because dragonflies mash their prey to a pulp with powerful serrated jaws. They are divided into two subgroups – the dragonflies and the damselflies. There are about 5500 different species of odonates worldwide, roughly equally divided between dragonflies and damselflies.116 species have been recorded in Hong Kong what is an amazing number for such a small area! France has around hundred and UK around 55 species to give you an idea about how spoiled we are with their presence.
While the adults are magnificent looking, the larvae are little known to most of us and dull looking. That is because they are aquatic creatures, living below the surface in freshwater streams and pools.
The larval stage of dragonflies can last for several years. The adult stage at the contrary is often a few weeks to a few months. During that short period the adult has to survive and breed. In the final stage of larval development, when the adult is ready to emerge, the larva has to make the transition from the water to the land.
The larvae of most species simply climb up the stems of emergent plants. Some however even climb high into trees. Once a site is found, the adult form slowly emerges, which can take 2-3 hours in dragonflies, 1 hour in damselflies. The shed larval skin is left in place; a good place to look for these is the water-lily pond at Tai Po Kau Forest which is actually one of my favourite spots in HK for birding and photography in general.
Freshly emerged dragonflies are like ghosts. Their wings are shiny, their bodies lacking pigments. It can take up to two weeks for a dragonfly to reach sexual maturity, during which time there is a transition to adult coloration. Subadult coloration can be different from that of the mature adult, and often lead to difficulties identifying the species.
Most of the behaviour that you will observe if you sit quietly by a pond or stream in summer is sexual in nature. Most male dragonflies establish a territory close to a suitable site for the female to lay her eggs. The male defends the territory against other intruding males while waiting for a female to fly by. Some species just perch and wait for this to happen ,others patrol the area for long periods rarely coming down to rest,time is precious this period of the year!
This is the part where it all becomes a bit grim if you ask me, maybe I am too romantic….
Most animal species at least go through some sort of courting routine before they mate; dragonflies don’t have that much time. So they forcefully mate with the first female they come across.
A male will first locate a female by he flight patterns to make sure she’s the right species. Then he approaches from behind, clamps his forearms around her neck and the pair flies or perches “in tandem”. This deters other males from trying to copulate with the female.Copulation usually follows within a few minutes of the tandem position. The male and female take up what is called the “wheel position”,
I know it all sounds a bit like the Kamasutra but you might have witnessed these in nature and wondered what it all is about. The reason for this is that the male has two separate sets of sexual organs. The primary sexual organ consists of a sperm-producing organ located near the tip of the abdomen. The secondary sexual organ is located higher up. Before copulation, and usually while the pair are in the tandem position, the male bends his abdomen so that sperm is transferred from the primary sexual organ to the secondary sexual organ. The female then curves her abdomen so her genitals (located at the tip of her abdomen) can connect. Hence the name ‘Wheel position’.
Female dragonflies will usually mate with multiple partners so competition for carrying on the genes is very high, that high that dragonflies have developed barbs on their penises that serve no other purpose besides scooping a previous suitor’s semen out of a female dragonfly.
In some cases, the male will continue to guard the female until she deposits the eggs to increase his chances of fatherhood.
I mentioned earlier that dragonflies are amongst the most brutal and well equipped killers.
To start with: their eyes are incredibly advanced.
Most insects have multifaceted eyes,house flies have about 6,000 eye facets that give them a panoramic view of their surroundings. But with 30,000 individual facets, dragonflies blow them—and every other insect—completely out of the water. Each facet creates its own image, and the dragonfly brain has eight pairs of descending visual neurons to compile those thousands of images into one single picture.
And it gets even crazier; dragonflies have visual senses that would be considered superpowers by any human standards. Human eyes have three proteins that sense light—giving us a color range of red, yellow and blue. Dragonfly eyes can have four or five, allowing them to perceive the normal color spectrum, along with UV light and the plane of light polarization (the effect you get with polarized sunglasses). This is believed to help them navigate and reduce the sun’s glare on a body of water.
The massive bulbous eyes of a dragonfly wrap around its head like an astronaut’s helmet, giving it a 360 degree view of the world. They can see you when they’re flying towards you, and they can see you when they’re flying away. Obviously, this is a valuable tool for escaping predators. dragonflies don’t have blind spots, and they’re notoriously hard to catch. They have been around for over 300 million years so yes they evolved accordingly.
One of the most distinguishing features of dragonflies is the way their wings work. Their four wings operate independently of each other, allowing it to maneuver in mid-air like a helicopter they can hover, fly forwards, backwards, and sideways, and instantly change direction whenever they need to. Dragonflies can even fly upside down if they need to.Dragonflies are the only insects with this amount of control over their wings, each wing is connected to the body with a separate muscle group.
In simple nervous systems, multiple objects tend to fade out; the insect can’t handle the attention multitasking.This technique is also used by birds in flocks and schools of fishes to confuse predators, safety in numbers. But dragonflies have the ability to switch their attention between objects at will. This selective attention span allows the dragonfly to single out one target in a swarm, then focus on it while remaining aware of the the rest of the swarm to avoid a collision.
All these features make them one of the most efficient hunters on the planet,they don’t chase but anticipate where the prey will be next, their success rate is a staggering 95 percent. Sharks, one of nature’s fiercest predators, only manage to catch about half of the prey they hunt. Lions are lucky to get their claws on a quarter of their targets.
Dragonflies do two things when they intercept their prey: first, their front legs curve up to cage it in, cutting off its escape. Second, their hinged jaws clamp down and shred the wings of the fly, immobilizing it. After that, they’re free to nibble down without any chance of losing their prey. Dragonfly jaws can open as wide as their own head allowing them to eat virtually anything within that range, and they’ll often consume their food in mid-air without even bothering to land.
Dragonfly larvae are even more cold-blooded than their adult counterparts when it comes to killing. Like many insects, dragonflies begin life with a larval stage. Dragonfly larvae, or nymphs, live underwater and scoot through the water by shooting a jet of water out their rectum, like tiny torpedoes. Some dragonflies live like this for up to five years, before spending a relatively short few months as an adult.
During their waterborne life, they hunt small insects and especially mosquito larvae, that are in the water with them. But in many species, the diet doesn’t stop there, some dragonfly larvae will even eat tadpoles and small fishes, snagging their prey with powerful jaws and the same vicious tenacity that will dictate their lives as adults.
Enjoy the beauty of the dragonflies on your hikes or hovering above you while taking a refreshing dip in a pool. They might be ferocious but they eat mosquitos so….we love them!
For great pictures check: The Asia Dragonfly website http://www.asia-dragonfly.net this site contains nearly 8,000 photographs of Asian dragonflies.