Sorry about the delay on day 5, but I forgot my hard drive at the lab Friday night, and was right back into heavy data collection yesterday. I post these nice images of insect flight now to make it up, starting with a lovely Longhorn Beetle of the genus Necydalis. Check out the short elytra and overall wasp-like appearance!
Next up, a housefly gets a surprise!
And finally, some lovely images of a Cabbage Looper taking off.
The flies of the family Syrphidae are some of the most accomplished of all insect aeronauts. Their agility, precision and speed are amazing to see, as they dart about flowers and freeze in motionless hovering flight. Like all winged flies, syrphids have one pair of wings only, (Diptera means “two wings”). Where the rear pair would be, there is a pair of knobbed appendages called halteres. These organs function to inform the fly of perturbations in two axes, allowing precise control of direction, speed and stability.
Without halteres, all flies become unable to maintain flight control. The precise means by which sensory information from the halteres is encoded and transmitted to the fly’s brain are not fully understood, but good physical models have been developed that implicate perception of strains associated with Coriolis forces on the beating halteres (if you hold a spinning bike tire and try to perturb it in planes perpendicular to the rotation, you will feel the Coriolis forces!).
OK, so enough physics! What do beating halteres look like? Have a look at this syrphid hovering and taking off.
It might not be super obvious, but it was surprising to me to note that the plane in which the halteres move differs by an angle of up to 30 degrees from that of the wings.
Syrphids also have high power relative to their mass, and this allows very rapid accelerations (making them difficult to catch).
As mentioned in my other post on wing coupling, other flying insects couple their wings to achieve formidable aerial prowess. Of course, having a single pair of wings is not the only way to be a master of the skies, as dragonflies are undoubtedly one of the most agile and versatile fliers, hovering and accelerating in spectacular fashion.
Syrphids though, with their bright coloration and super high performance enabled by halteres, high power to weight ratio, and fascinating life history, are undoubtedly one of my favorite fly families.
Doing these high speed videos has been a real eye-opener for me. I am amazed at how slowing down the movements of even common insects brings forth a new world to marvel at. It is reminiscent of the feeling of being a new macro photographer and just photographing insects constantly for the wonder of it all*.
So, the title refers tho the fact that every arthropod in this post displays some degree of hopping, skipping or jumping.
We start with a froghopper, the familiar Meadow Spittlebug, Philaenus spumarius. This insect, when disturbed, takes off at such a high rate that I had to record it at 6400 fps, and even then it was not totally frozen in each frame! I love the spiralling trajectory of these bulletlike insects.
This next video will show you exactly why a skipper (a butterfly in the family Hesperiiidae) is called a Skipper. These butterflies actually skip every few wingbeats, which gives their flight a real unpredictable jerkiness that likely helps them evade predators.
The following videos show a few examples of Neuropterans jumping as they take off, affording them a clear area for the downstroke of their relatively massive wings. The Green Lacewings are often referred to as “fairylike” in the appearance of their flight, as their light wing loading and bright colors make them seem like little winged sprites.
.I really wanted to shoot a grasshopper hopping, but for some reason there seems to be a real lack of them (perhaps they are suffering due to our month-long drought in Vancouver)! Anyway, I hope you enjoyed the videos. Let me know which you think is the coolest!
*actually, I am still in that phase!
Most large beetles, in comparison to flies, wasps and dragonflies seem slow and cumbersome in flight. Perhaps this is due to their forewings being modified into protective covers for the abdomen rather than full aerodynamic partners. Instead, many beetles hold their forewings (called elytra) aloft ahead of their membranous hindwings, contributing to stability and lift at high airspeeds only (note that they often hold them at a high dihedral, which is a stable configuration).
Certain beetles have much more agility in flight, and acheive this by closing their forewings across their abdomens after their hindwings are deployed. If you have ever tried casing down a Trichiotinus flower scarab in flight, you can appreciate their advantage!
Putting all that hindwing under the elytra takes a bit of origami. Compare the folding of the soldier beetle (Rhagonycha fulva, Cantharidae) above with the ladybird below.
Beetles are hyper-diverse, and very prominent in all kinds of ecosystems, so it seems that their (on average) less agile flight has not been a big penalty. The way that they gracefully unfold their wings and reach skyward during takeoff seems somewhat hopeful to me for some reason. And however much their flight performance lacks compared to a housefly, I still remember that almost any beetle can fly a lot better than I can!
This weekend, we began work with a new high speed camera, a Photron SA-5, with a wicked large sensor capable of recording 7500 frames per second at its full 1024 by 1024 pixel square sensor (and higher speeds at lower resolution). This beastly machine is being used by Mike Hrabar and myself to describe some little-understood phenomena around insect locomotion and behavior, which will hopefully be incorporated into a future paper. The rental of this machine is pricy, and the time when our study species is active is small, so in the downtime we have been using it for all kinds of insect imaging for fun and education. I invite you to join me this week for High-Speed Insect Science (just in case the Shark Week Fiasco has got you down).
Let us begin!
Like many insects, adult Hymenoptera have two pairs of wings on the middle and rear segments of their thorax. These wings beat in unison, and are effectively a single pair of aerodynamic surfaces. They are coupled with a tiny row of hooks (hamuli,; a single one of which is a hamulus) on the leading edge of the hindwing which grab a small fold on the trailing edge of the forewing. In the above video of Polistes dominula taking off, note how the wings beat as one unit, connected by the hamuli. For a close up view of hamuli, check out these shots by flickr user Yersinia pestis.
Sometimes the wings become uncoupled, like when the insect moves through vegetation or after a predator attack. The wings may still re-couple, as they do for this Leafcutter (Megachilid) bee during takeoff:
What is interesting to me is how the decoupled wing seems to make the Megachilid lose lift and bank to the left as it falls, something that indicates a severe aerodynamic stall on that side of the insect. The bee recovered and flew away rapidly, and it wasn’t until the video was saved that I managed to see this temporary decoupling. After the shoot, I found a nice retirement spot for this tattered-looking bee:
Large bees, such as this Bombus vosnensenskii also benefit from the large coupled wing area made possible by hamuli. This, combined with their large thoraces bursting with powerful flight muscles, allow these relative giants to power into vertical takeoffs.
These bees care not for pseudoscience!
Other insect orders also couple their wings with hamuli, such as aphids and male scale insects (Hemiptera), but moths and butterflies use a different structure called a frenulum which hooks into a fold or invagination called a retinaculum.
Hamuli are wonderfully useful structures for the lifestyle of the flying hymenopteran, but they can also be important aids to species identification, as the numbers of hooks may vary between different groups.
Well, I hope you have learned something about wing coupling in Hymenoptera, or at least enjoyed the videos. I will try to get another post ready for tomorrow, depending on what our research schedule is like. Thanks for tuning in!
PS. These are so fun! Here is a shot of a male Polistes dominula making a beautiful takeoff.