Wednesday, November 21, 2012

Season's Feastings, the Odonate Way

It’s Thanksgiving time in the US, and I’ve been wondering how I could possibly tie a post about dragonflies and damselflies to the holiday. It’s far too chilly and sunless around here to show any odonates enjoying the season. The best I could come up with was a bunch of photos of dragonflies and damselflies eating to their hearts’ content. That is, after all, how many Thanksgiving celebrants observe the day.

All odonates are predators in both the nymph and adult stages. No vegetarians in this bunch! While the nymphs’ aquatic diet is more broad (essentially whatever they can catch and subdue with their extendable labium), adults primarily target other flying insects. Their prey is frequently much smaller than themselves, but they will occasionally dine on more substantial meals too. Some species specialize in taking larger prey.

I looked through my photo collection and picked some examples of dragonflies and damselflies in the middle of chowing a rib-sticking meal (I know, they don’t have ribs). Don’t presume that these are necessarily representative. It’s just that a dragonfly eating a tiny little midge or fruit fly doesn’t offer the same visual impact as one consuming a hearty meal, and I wanted to show you some odonates really stuffing their little faces. Qualifying candidates were those devouring prey about as big or bigger than the diner’s head. These photos are not to scale . . .

1. Male Paddle-tailed Darner, Aeshna palmata, with what appears to be the abdomen of a large crane fly.
2. Male Ischnura fluviatilis with a leaf hopper.
3. Male Olive Clubtail, Stylurus olivaceus, with a beetle. A recycled image from a post about this species.
4. Male Dragonhunter, Hagenius brevistylus, with a female Powdered Dancer, Argia moesta.
5. Male Western Pondhawk, Erythemis collocata, with a butterfly (appears to be a Gray Hairstreak, Strymon melinus). Note the butterfly's wing scales all over the pondhawk's face and eyes.
6. Immature male Columbia Clubtail, Gomphus lynnae, with a dragonfly (but not enough left to tell what it is).

7. Male Eastern Pondhawk, Erythemis simplicicollis, with a male Eastern Amberwing, Perithemis tenera.
8. Male Mesamphiagrion dunklei with a leaf hopper.
9. Female Emerald Spreadwing, Lestes dryas, with a teneral male Northern Spreadwing, L. disjunctus. The prey was actually longer than the predator in this case!
10. Female Black-fronted Forktail, Ischnura denticollis, with some sort of fly.
11. Female Hoary Skimmer, Libellula nodisticta, with a female Spotted Spreadwing, Lestes congener. This case is unusual in that she didn't start at the spreadwing's head—kind of like starting on your slice of pizza at the crust.
12. Female Four-spotted Skimmer, Libellula quadrimaculata, with a teneral meadowhawk—probably White-faced, Sympetrum obtrusum.

Well, there are definitely some cases of eyes-bigger-than-stomach-ism! I’m sure you noticed that the main course in half of those photos are dragonflies and damselflies too. Odonates preying on odonates is not uncommon—particularly by some voracious predators like the Dragonhunter (photo 4) and the pondhawks (photos 5 and 7)—but it’s not as common as these photos make it seem. Remember, I was going with visual impact, not necessarily with what is representative.

I hope these dragonflies and damselflies are thankful for their bounty. Well, not so much the ones that are the bounty, but that’s how it works in nature; predators are sometimes prey. Along with the other joys that odonates bring to our lives, we can be thankful for their harvesting of the little annoying, biting, disease-transmitting flies . . .   . . . that is, when they aren’t stuffing themselves with more photogenic prey.


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