Terminal Velocity – Ant Style

If you are a paleontologist lucky enough to have run into me at a cocktail party recently, you have probably been subjected to a diatribe concerning arthropod life history patterns, dispersal strategies, cladogenesis and the origins of insect flight. Sorry again about that.

Now, via Rollicking Boils, comes this NYT article about "gliding ants."

Those with an afternoon to kill should probably spend it watching the videos.

Having not yet read the Nature paper, here are my poorly-informed, unqualified opinions:

"…this is fucking awesome." I concur. (Note: this quote comes from the person who sent me the link, the rest are from the NYT article)

"…may reveal the origins of insect flight." Not so sure. As Yanoviak states clearly in the gliding ants FAQ ants are a highly derived group of insects and workers are secondarily wingless. Reproductive adults (queens and drones) are born with wings which they employ to full effect during their nuptial flight. Thus these ants are a poor analog for the earliest insect fliers and it's hard to imagine a scenario which would lead to these ants developing powered flight.

"There are very few similarities between insect gliders and other gliders." Well, beyond the superficial dissimilarity (i.e. no gliding membrane¹), gliding ants seem to me quite similar to gliding vertebrates in that they:a) Are arboreal as a rule. Though note that not all arboreal ants (nor vertebrates for that matter) are gliders. (Anyone know if this is also the case for the flying silverfish mentioned in the article?)b) Use gliding as a means for predator-evasion and locomotion but not for prey-capture or reproductive dispersal.c) Have independently evolved gliding habits multiple times within different lineages. Much as several unrelated arboreal mammals (flying squirrels, sugar gliders, colugo etc.) have.

"The scientists' hunch that the ants' movements, not their body shapes, chiefly dictated their gliding paths was confirmed when they started chopping off appendages to see if the insects could still soar." I love this kind of old-school field biology, no electrophoresis trays, no centrifuges, not even any randomly distributed plots, just some guys chopping the legs off of ants, dropping them from trees and videotaping it.Nevertheless, take a close look at the head of Daceton:

Beautiful photograph courtesy of April Nobile and the Cal Academy of SciencesBroad and flat, with rear projecting lobes (and even little spoilers on the thorax?)…I think there is a good chance that these ants DO exhibit morphological adaptations related to this behavior beyond just the acrobatic techniques emphasized in the NYT article. In fact this looks like an awesome functional morphology/biomechanics project for anyone with access to a very tiny wind-tunnel

The NYT article and this one from Cal hint at a different model of insect evolution than the "mayfly skipping across the pond with modified gills" story that was once in vogue. It is interesting to note that the explosion of flying insects seems to correspond with the advent of forests in the Carboniferous.

Will we eventually see a full-blown "tree down" vs. "ground (or pond) up" debate like the one which is at the core of current research into the origins of bird flight?

More on my notions about the origins of insect flight in an upcoming post.

¹ – Given that ants are several orders of magnitude smaller and lighter than vertebrate gliders it is fairly unsuprising that ants would not develop gliding membranes. First, they are unneccesary for an organism with such a large surface area:mass. Second, gliding membranes on such a light organism would probably be a liability (imagine ants being whisked away involuntarily with every small gust).

Tags: evolution, insects, origins of flight