Note to self, get better work boots, don’t ask why but the ones I have are awful and keep leaking despite being waterproofed just last week. Things that aren’t awful include the Palm Nut Vulture which was the focus of last week’s blog.
And steering back to awful, the answer to last week’s mystery murder was f. This savanna crime scene drama is based off a real life case from Zimbabwe, where over the course of two days 500 animals were found dead or dying after feeding off an elephant killed by poachers. The body was laced with cyanide in an attempt to reduce the number of scavengers, which can alert rangers to the presence of poachers.
With that dealt with we now turn our attention to a smaller, albeit more deadly aerial killer, hope you guys enjoy.
Issue #164 – Brown Hawker
Kingdom – Animalia
Phylum – Arthropoda
Class – Insecta
Order – Odonta
Family – Aeshnidae
Genus – Aeshna
Species – grandis
Related Species - The Brown Hawker is one of a number of large dragonfly species found in the family Aeshnidae, also known as the Hawkers.
Range - Brown Hawker’s can be found across the lowlands and wooded margins of Central Europe, as well as the United Kingdom and the Low Countries
Brown Hawker’s are large chocolate brown dragonflies, with an average body length of 7cm. This species is fairly easy to identify because it is one of a few species, and the only fairly common one, to have brown tinting to the veins in its wings, although this is far more apparent in the males than in the females. Both genders have rows of yellow stripes running up and down their flanks, and male hawkers can be distinguished from females by additional blue markings on the thorax and abdomen.
As their name suggests, the Brown Hawkers, and by extension all dragonflies classified as ‘Hawkers’, are active predators that patrol their territories looking for prey, rivals and potential mates. Should the former be seen, the Brown Hawker will intercept its prey mid-flight and bring it to a feeding perch, before shredding it with its mandibles in order to make eating its captured victim easier (2). Potential mates are seized in much the same way, with the male forming a heart like structure with his abdomen positioned over the females thorax, while her abdomen and reproductive organs are positioned above the secondary pair of gonads on the male’s thorax (3).
The female Brown Hawker will lay her eggs shortly after mating, with both her and her mate dying after reproduction. These eggs will hatch into aquatic ‘nymphs’ which share many morphological features with the adults save for the wings, although later moults begin to show signs of vestigial wings beginning to form. Like the adults, these nymphs are predatory, and will feed on tadpoles and small fish as well as other invertebrates, catching their intended prey by pumping water into the body to propel the extendable pair of jaws, known as a ‘mask’ out into the victim. Eventually, after a period of a few years, the nymph leaves the water at night and completes one final moult of its skin before emerging as a winged reproductive adult or imago.
Five Fun Brown Hawker Facts
Uniquely among insects, each separate wing of dragonflies and damselflies are controlled independently by a single muscle. Because of this dragonflies can hover for prolonged periods of time and even fly backwards.
To aid them in flight, the eyes of a dragonfly are comprised of light sensitive cells known as ommatidia. The eyes of the Brown Hawker contain up to 22500 of these cells, and allow it an almost 360 degree field of vision.
Brilliant vision and skilled powered flight make the Hawker dragonflies some of the most effective predators in the world. Around 95% of attack runs result in the dragonfly making a kill (4). In contrast Great White Shark (Carcharodoncarcharia) only achieve a kill with a little over half of all attacks while Lions (Panthera leo) only get a kill with 25% of their attacks.
Male Dragonflies transfer sperm from their primary gonads at the rear of the abdomen to their secondary gonads mounted on their thorax to aid in reproduction.
Despite the modern day association of dragonflies with grace and elegance, they weren’t always seen as such. Many dragonflies, especially the Hawekers, are known as darners, a relict term coming from the belief that such insects were the ‘devil’s darning needles’ that he used to poke the eyes out of his victims. In some places in Europe such as Portugal and Norway, dragonflies are still referred to as tira-olhos (eye-snatcher) and Øyenstikker (eye-poker) in their respective languages (5).
2 - Powell, Dan (1999). A Guide to the Dragonflies of Great Britain. Arlequin Press.
3 - Nachtigall, W (2013) Biological Mechanisms of Attachment: The Comparative Morphology and Bioengineering of Organs for Linkage, Suction, and Adhesion
4 - http://www.natureworldnews.com/articles/1216/20130404/master-hunter-dragonflies-kill-prey-95-percent-time.htm
5 - http://www.petzon.se/dragonfly/main/just_for_fun/folklore.html
1 - https://www.rutlandwater.org.uk/wp-content/gallery/dragonflies/BrownHawker-f.jpeg
2 - https://farm8.staticflickr.com/7260/7882949164_4a0d25b7a4_b.jpg
3 - https://c2.staticflickr.com/8/7745/18431008761_900312f728_b.jpg
4 - http://hampshiredragonflies.co.uk/wordpress/wp-content/uploads/2013/07/D90_38242.jpg
I like dragonflies, always have, always will despite how brutal they are. Next week we swap high speed offence with defence as we meet a slow lumbering yet very persistent predator. But until then make sure to critic, comment and suggest future issues as well as making sure you check past issues in Impurest’s Bestiary
Want more IGTA? For another fast moving predatory insect, click here to see the Green Tiger Beetle. Or for something even more insidious, click here to see another airborne assassin, the ruthless Robber Fly.