Tag Archives: insects

Facing the facts: delighting in dragonflies

My ‘friend’ Adam Hayward is a postdoctoral researcher at the University of Edinburgh. His research involves the study of ageing, for which he typically uses detailed life history records from long-term studies of mammals (including sheep, elephants and humans). This means he does not have to perform experiments, instead waiting patiently until the data thwacks – like a heady, elephantine slab of numerical excrement – onto his desk. Hayward likes to mock the organisms studied by my erstwhile labmates and me: insects and other invertebrates are, he claims, innately uninteresting because they “do not have faces”.

It’s time to present some evidence to the contrary.

Check out this delighted little Odonate!

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What’s this guy smiling about? Check out his view!

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This little dude’s offering you an invisible present and IT’S ADORABLE

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That’s quite a few delightful images there. Do you have something in your eye? Our little pal here just wants to know if you’re ok. Are you ok? You ok, buddy?

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Why is this chap so happy? Look closely – it’s because he’s chewing up a delicious insect meal he’s just captured in his powerful chewing mouthparts!

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wait

no

OH GOD

THEY AREN’T SMILING AT ALL

THEY’RE JUST FLEXING THEIR HORRIFYING DEATH-DEALING MANDIBLES

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That’s right, dragonflies use their powerful mouthparts to catch their prey in mid-air and then chew and grind them to smithereens. Indeed, ‘Odonata’ (the order comprising dragonflies and damselflies) finds its origin in the Greek word ‘odonto-‘, meaning ‘tooth’, and referring to these strong mandibles. Dragonfly prey is typically other insects, although it seems they are not against kicking it up a notch:

Unfortunately, I couldn’t find much research into the mechanisms behind adult dragonfly mouthparts, but that might be because everyone is a little too focused on the larval stage. Check out The Dragonfly Woman‘s post on ‘Why Dragonflies are the Best Insects‘ for some cool info on extendable mouthparts (in addition to a jet-propulsion rectal chamber, which I think is something I’ll be adding to my xmas wish list). Dragonflies have all manner of interesting behaviours and adaptations, and Stanislav Gorb‘s research into the ‘arresting’ mechanism of adult dragonfly heads is worth a read: complex microstructures fix the head in position while feeding or flying in tandem, helping stabilise gaze and avoid violent mechanical disturbance. Tandem flights are what dragonflies do after mating, which tends to be a good time to stabilise that gaze and avoid pesky violent mechanical disturbances.

Of course, the fact that a dragonfly’s expression is due to intense feeding power rather than whimsy does not mean that it is faceless. I use this post to demand an apology from Dr. Hayward! However, I fear that I have gone overboard in taking his denigrations of invertebrates at face value; somewhat ironically, it is difficult to verify the true representation of his feelings because his own face is coated in a thick, glossy coat of hair.

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…which suddenly seems extremely suspicious… perhaps worthy of a closer look…

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OH GOD

NO

RUNNNNNNNNNN

From the shadows, they come.

Drawn by the scent of their hapless prey.

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Their victims are powerless to defend themselves…
IMG_5511Sweet, delicate flesh is ripped and torn as attacks come from all sides…

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They shiver with feverish excitement…

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…as the attack turns into a frenzy of shredding, chewing maws…

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Some emerge from the writhing mass, their faces slick with gore…

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Meanwhile, the young look on in horror, knowing that soon it will be their turn to face the onslaught.

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Before long, all that is left are the dry husks of what was once a thriving group.

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Leaving our hunters to move on, covered in the bloody remnants of their latest success, in search of new victims.

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But they are not the only ones on the prowl today.

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My nature photos of 2012

I have started a new ‘tradition’ at home, in which I create a calendar of some photos that I’ve taken over the previous 12 months; I just finished the one for this year, so thought that I’d put up the photos that I have selected (including a couple of bonus mammal shots to round out the animal groups a little…!).

In 2012, I’ve been lucky enough to travel around Scotland a fair amount, and got a few nature firsts here – crossbills, vivaparous lizards, and finally saw the magnificent capercaillie (and ran away from it as it chased me and a very famous evolutionary biology professor up a path!). I also went to Sweden for a quantitative genetics workshop (where I learnt to love long johns as much as matrix algebra), took a trip to Canada (where I gave my first talk at a major international conference, Evolution 2012), and holidayed in Barbados (where Kirsty and I celebrated our engagement). The final bonus photo in this gallery is actually from 2013, and I hope it is a portent of good things to come!

I’m going to post this to Alex Wild’s request for end-of-year photo sets as well; mine certainly won’t compete with most of those on show, so you should go and check them out! There is some RIDICULOUS stuff going on. Hopefully I’ll have a competitive selection next year, as I’m off to Borneo in July for my honeymoon! That’s right: I’m getting married, like a real grown-up person.

Note: I’ve noticed that various people have ended up here after searching for rogue capercaillie in Speyside… I can’t give out the location myself, but I will say that we were taken there by a local wildlife guide, Steve Reddick, who was an excellent host and whose rates are also extremely reasonable!

Latest addition

A new entry to my household is this rather wonderful specimen – a ghost mantis (Phyllocrania paradoxa), courtesy of Ornamental Insects. My macro attachment will come in useful – it’s around a centimetre long now, and will grow to only around 5cm. Sexual dimorphism in adulthood is not too pronounced – females are larger, though have less abdominal segments, while males have longer antennae. The crest on the head is fairly impressive… as was the way it was chomping through a fruit fly when I opened the tub this morning! This one is at an early instar, so I will be sure to photo-document each stage if possible.

Ghost mantis snacking on some drosophila

I had a quick search on Google Scholar, but it seems like they haven’t been studied too much outside basic behavioural and ecological work – hopefully I’ll be able to dig up something cool about them or their nearest relatives though. Either that, or I’ll have to buy in a load more and do some studies myself. If anyone wants to pay me to do so, I can add a paypal button to my site…! In the meantime, you can content yourself with a little read of a post I wrote previously on sexual cannibalism in mantids.

The Praying Mantis: an unfairly maligned sexual cannibal?

Recently, probably due to the incredible macro photography of Igor Siwanowicz that I linked to recently, I’ve become rather obsessed with mantises. Before then, I’d paid very little attention to these weird creatures, and will admit to having been mildly terrified of them in the past. This stemmed from an unfortunate incident many years ago, when I tried to brush one off the door handle of a holiday apartment, only to learn that they can fly – and can propel themselves rapidly towards a human face. The neighbours came rushing out because they had heard what they assumed to be the cleaning lady screaming. Anyway, possibly due to this, I thought that there was just a ‘praying mantis’, and had no idea that the order could range from this:

Mantis by Igor Siwanowicz

to this:

Mantises by Igor Siwanowicz

…and many more incredible shapes, sizes and colours. The displays that a mantis can produce when threatened are really quite incredible, and I have been told that they are great for use in undergraduate practical classes. Mantises are apparently relatively short-sighted, and so two can be placed on opposing ends of a mounted piece of string, and it will suddenly become very clear when they notice each other. Unfortunately, the ‘loser’ will signify defeat by flying off to a remote corner of the classroom, delaying the end of the lesson as the tutor (or, more likely, a hapless TA) climbs up to gingerly retrieve it. Here are two videos of different mantis displays, the first relying on sound and wing movement, the other on the large peacock-style eyes on its wings:

So, what wonders does the mantis have in store for the intrepid sex researcher? Rather distressingly, the answer is sexual cannibalism. Males are smaller than females, which have voracious appetites and can eat up to 16 crickets per day, and so put themselves in a rather precarious position both prior to and during copulation. There is a lot of evidence, including the video below (complete with rather breathless commentary), of females devouring their mates during intercourse, but a controversy remains over the function of this.

Does the male, as in the case of the redback spider, allow himself to be eaten in order that the bearer of his children has a large meal when times are scarce, therefore helping to furnish his offspring with added nutrition? Some other insects allow females to ‘nibble’ on them during sex, thus lengthening the duration of copulation and enabling more sperm to enter the female and fertilise the eggs – could it be that this is a poorly-judged version of this adaptation? The latter seems unlikely, as females generally remove the head first, and although the body continues its final mindless act, studies have shown that ejaculation tends to happen more rapidly after decapitation, if at all.

A 2010 study by Kate Barry, of Macquarie University in Sydney, Australia, investigated the state of female nutritional status on mating dynamics in a sexually cannibalistic praying mantid. Previous studies have shown that scramble competition is important in these mating systems, and thus males are selected for their ability to detect and locate females. Given that each copulation holds the risk of death for the male (and the inherent fitness costs of this occurring), and that condition has been shown to be positively correlated with fecundity in female mantises, then theory would predict the evolution of strong male choice for females in good condition. A female in good condition is not only likely to have more eggs, making her a good choice for a male wanting to ensure that he makes the most of the copulation should it be his last, but is less likely to be starved of food. Interestingly, Barry found that long-distance male attraction to females is somehow linked to female fecundity, with ‘low condition’ females still being attractive to males as long as they had a base level of fecundity. Nutritional status seemed to have no bearing on male choice, and so it would appear that females may produce a pheromone that indicates fecundity. Indeed, in a species of cockroach there exists a relationship between ovarian development and pheromone production, meaning an honest signal is produced to demonstrate a female’s egg-bearing capacity.

It would seem, then, that the unfortunate decapitated males may be those that were unable to secure copulation with high-fecundity females, and sacrificed themselves in a final desperate attempt to pass on their genes. Or perhaps, as can happen in many species, they simply read the signals wrongly.

Read KL Barry’s paper here: http://dx.doi.org/10.1016/j.anbehav.2010.05.024

Note: since becoming more interested in the mantis, I’ve even come so far around as to having decided to place an order with Ornamental Insects for a ghost mantis, after listening to their interview on John F Taylor’s Reptile Living Room radio show. However, you may be able to tell from the picture below that, perhaps, I haven’t quite conquered my fear outright…

Ghost mantis by Ornamental Insects