May 17, 2012
Two weeks ago I told you I'd fill you in when I found dragonfly nymphs in our pond. I wasn't expecting to be able to give you this update so quickly, but SURPRISE, nature moves fast, people! In the last few weeks, I've found more than 50 dragonfly exuviae (the papery exoskeletons shed between molts) attached to the rocks of the pond. Of course, this prompted me to take out my dip net and look for nymphs in the water.Here's a picture of one I found:
Variegated Meadowhawk, Sympetrum corruptum, nymphFound May 5, 2012While I was dipping for the dragonfly nymphs, I found a lot of other macro-invertebrates. The list isn't very long, yet, but includes immature mosquitoes, chironomid midges, mayflies, and predacious diving beetles!
Mayfly nymph found May 5, 2012
Predacious diving beetle larva found in pondMay 4, 2012
I also found an adult predacious diving beetleonMay 5, 2012
May 3, 2012
Last night I hosted an InSEX dinner at an undisclosed and secret location. No, we weren't eating insects (in fact, we had a lovely vegetarian meal). Instead, we were discussing their weird, wonderful, and various reproductive strategies!
Vietnamese Walking Stick, Baculum extradentatum
A great example of asexual reproduction
I also took some impressive beetles to show off
Here's an excerpt:
Sperm Wars-Unlike honeybees, dragonflies don't have exploding penises. Instead, they have an equally impressive mode of sperm competition. When a male dragonfly grabs a mate—clasping her roughly behind the head—he carries her away for a nuptial flight. After some brief struggling, the male bends his abdomen around and inserts his aedeagus (that's insect for penis) into her reproductive tract. With his impressively spiked member he scoops out the sperm left over from a previous mating, thus ensuring it is his sperm and no other's that will fertilize the eggs she is about to lay...
But how does this all relate to the North Campus and L.A.'s urban nature? Simple—we found our first dragonfly at the pond! According to Museum Ornithologist, Kimball Garrett (yes, he does dragonfly identification too), this is a male Variegated Meadowhawk, Sympetrum corruptum. He was sunning himself on a rock, possibly waiting for a female dragonfly to make an appearance. Unfortunately for him, none showed up while I was there.
Over the next few months, the pond will attract more and more adult dragonflies and, soon enough, we'll have them mating. In tandem, the coupled dragonflies will approach the water's surface and the female will lay her eggs. Unbeknownst to many, the immature form of dragonflies actually live underwater! After the eggs hatch, the dragonfly nymphs will find a cozy spot to hide in the reeds. It's a dangerous and murky life down there, I mean who would want to get eaten by a fish? One way that dragonflies can evade predators is through jet propulsion. They pull water into their rectal chamber and eject it at high speed, thereby propelling themselves in a forward direction, and hopefully out of harm's way.
When they're not trying to evade their own predators, dragonfly nymphs are voracious predators themselves! They have extendable mouthparts that can be "shot" out of their heads in less than three one-hundredths of a second. This is very fast indeed, and allows the nymphs to sit and wait until something comes within mouth's reach. As you can tell, dragonflies are much more than just pretty insects good for putting on greeting cards and tattooing onto various bodyparts. I mean, what other creature can you think of that has jaws of death, rectal propulsion, and a highly modified penis for sperm removal?
Male Variegated Meadowhawk basking in the sun