Monthly Archives: September 2012
Aaaand we’re off – to see if some of my caterpillars are chemically protected.
This is my arm right now:
I’m about to go rub some caterpillars on another lab member.
(It’s ok, we’ve filled out the human testing protocol paperwork.)
So far I’m intrigued that these three species have all given me the same type of reaction in terms of timing, appearance, and sensation (it burns, and then itches). Other people in the lab have reacted to them as well, but I want to document this in a systematic fashion. It could be an important phylogenetic character. So far we’re pretty sure two of them are in the same clade, and the other we are going to add to our molecular dataset soon.
Here I am with some caterpillars (Acronicta impleta)… that I am about to start testing for chemical defenses by rubbing them on my arm. From a few reactions I’ve had, it seems there is one clade within the genus Acronicta which are chemically protected. I am still sporting a rash from a caterpillar I rubbed on my arm a week ago. For science!
Harrisimemna trisignata is an unusual animal. It has so many bizarre adaptations it’s difficult to know where to start. So, I’ll start with some pictures and a video, then give my thoughts. It is in the subfamily Acronictinae (family Noctuidae), which is why I am rearing it.
Harrisimemna trisignata appears to be a bird dropping mimic. Its coloration is beautiful to us, yet probably looks disgusting to a bird. It even looks like it has runny uric acid dropping down the sides of its body. However… it does not sit like a bird dropping mimic. Instead it arches its back, almost reaching its last segment with its head. Every time I look at my caterpillars, they are in that pose. They also have a bizarrely shaped pair of third thoracic legs. Not sure why?
Also, they have a habit of attaching their shed head capsules to the hairs just behind their head. As you can see in the video, they appear to use this head capsule as a mace to ward off attackers. Sometimes these capsules will stack on top of each other in a chain, though they usually fall off and they just have one at a time.
And they shake! They shake when I open the container, when I breathe on them, when I talk to them, when I touch them, when I look at them the wrong way. I can just imagine a potential parasitoid, like a tiny wasp, trying to land on that caterpillar… between the shaking and the head capsule whipping, I doubt it would stick around.
And of course the jumping spider mimic butt. Doesn’t it look like it has a few pairs of eyes on the back? In the last instar (the above photos are second to last) the appearance of a crouched jumping spider is even more dramatic.
They are also ball rollers. When they did their pupal chambers in wood, instead of just chewing up the wood like most caterpillars, they roll it up into neat little balls, then throw them aside. A few genera in the subfamily Acronictinae have this behavior. So far our molecular work has placed them at the base of the tree.
What does this all mean? This caterpillar is a remarkable animal which still has many more surprises in store, I am sure. I am really hoping to rear it again next year to study its behaviors.
For further reading:
Last weekend we took the general entomology class to the Yale Camp at the Great Mountain Forest in Norfolk, CT. We joined up with the general entomology class from Yale. Dave likes to plan this trip every time he teaches the course. Not only do the students catch a lot of insects, but it allows for good class bonding time, since we encourage a lot of interaction during the lab portion of the course.
Even though there was a severe storm Saturday afternoon, we were able to make the most of our time there. Lots of blacklighting Friday night, a late night caterpillar walk, sorting and pinning specimens, quizzing the students to help them study, lounging by the fireplace, insect charades, and staying up late gossiping. Some people left Saturday night, some left early Sunday, and some of us went for a beautiful morning hike. I caught about a dozen Acronicta caterpillars on red and white oak – really important for my research. So I was quite pleased.
Here are a few pictures from the weekend… check out our class flickr page for more.
Dave giving a lecture on caterpillars.
At one of the many blacklighting set-ups we had going. Lots of insects, and lots of red efts that came to eat them!
Two of my little Acronicta caterpillars. Aren’t they adorable?
The biggest caterpillar you will ever see in the northeast – Hyalophora cecropia. He spun his cocoon the next day.