Monthly Archives: June 2012
Sawflies, suborder Symphyta, are in the order Hymentoptera alongside bees, wasps, and ants. Their larvae are remarkably caterpillar-like, sometimes confounding entomologists until the larvae are observed up close.
There are some key differences: sawflies have many more prolegs than lepidopteran caterpillars (lep caterpillars have a maximum of 5 pairs, sawflies have 6 pairs or more), and they have only one eyespot on each side of the head (lep caterpillars have 6 stemmata arranged in a half-circle).
For some reason, the eyespots creep me out. I keep thinking that it should make them even more cartoonish and adorable, but I just cannot get on board with loving sawfly larvae. What do you think? Is this guy creepy or cute? Sawfly larvae can be gregarious, and give themselves away with characteristic resting poses. If you see a bunch of caterpillars along a leaf edge waving their rear ends in the air, you are looking at some sawfly larvae. They also tend to have a slimy looking sheen to them.
Oh, and did I mention some species spit?
They spit. At least this one does, in the family Cimbicidae. Many sawfly larvae simply regurgitate their nastiness, but these have the audacity to express fluid in a stream from glands above their spiracles.
Interestingly, in some parts of the world sawfly larvae are called “spitfires”, even though they do not spit forcibly – instead regurgitating fluid or everting it from glands. Only some species in Cimbicidae can actually hit you in the face from a tree branch a foot away (which the one in the video did, before I started filming).
For more information:
Eisner, T. 1994. Integumental Slime and Wax Secretion: Defensive adaptations of sawfly larvae. Journal of Chemical Ecology, 20:10. Link
While at Hurd State Park last week, we came across a few caterpillars very intent on hiding.
This one chose to cling to the midrib on the underside of a leaf. It managed to select a section just the right width to blend in. It was only the bright sun back-lighting the leaf that allowed us to spot the caterpillar easily.
This one was quite sneaky – slipping into a little crack in a tree. It was right in front of me and I didn’t notice until it was pointed out.
Have you observed any insects lately which have been very intent on not being seen? I would love to see more examples! Especially of caterpillars (of course).
Last week I went black-lighting with a few lab-partners-in-crime. I didn’t get many Acronicta (seems to be a theme this summer) but we had fun exploring the woods at night.
One thing we pondered… what’s with all the cockroaches in the trees? Here is a youngster.
This adult was calmly grooming her legs and antennae.
There seemed to be a cockroach on every stump (a lot of beaver damage in the forest) and one or two per tree trunk. I think they are beautiful little animals (as long as they are not in my kitchen), so it was quite fun! Just… unexpected.
Here are some other things we saw…
A cool caterpillar nibbling on lichen.
A geometrid caterpillar trying really hard to be a twig.
There were many beautiful leopard slugs in the trees as well. I would love to catch some mating one day! That scene from Life in the Undergrowth is one of my favorites of all time. Check it out HERE. Your life will never be the same.
Many of the june beetles were mating. I think they look sort of like little turtles.
Overall, we had a fun night! Though, while drinking from lab vials, I realized I am allergic to gin. Afterwards I learned that it runs in my family. Oops! My throat got really sore and started to close up, but I recovered.
On Thursday I went out into the field (Hurd State Park) to help some entomologists from another lab with their caterpillar collecting. They were also kind enough to lend me some supplies for my field experiments, which I am hoping to set up sometime this week once my caterpillars are large enough.
We saw many interesting organisms and interactions while we were out in the field. There were two cases of caterpillar predation which we observed directly. One was being carried by an ant…
And another was in the jaws of a jumping spider.
More stories/photos/videos are on their way!
My friend and I have a brilliant collaboration in progress: he writes dirty limericks about the sexual habits (courtship, mating itself, sexual characteristics and habits, etc) of insect and other arthropods, and I illustrate them. So far they are line drawings, I am debating on how to color them. We are hoping to turn our venture into a blog, and eventually a book.
One of the problems we are running into, however, is source material for my drawings. We would love to tackle things like the bizarre foot nibbling courtship of vinegaroons, but I probably will not get photos of that myself.
My illustrations are all free-hand, so nothing would be a trace or direct copy, but I do not want anyone feeling put-off if they can tell I used their image as a reference. I will be contacting some photographers directly. But if YOU have photos of insects doing what they do best and would like to share, please let me know! We would especially appreciate any little stories or descriptions of what is happening, to inspire us. I know there is a whole world of amazing insect sex out there, and we would love to explore it. You will be credited for your contribution unless you wish to remain anonymous.
Here is an example of some twisted up craneflies mating.
You can send me an email through the contact page of my blog. Thanks!
… to open my car door when I go to the Crossfit gym.
The field by the parking lot is swarming with deer flies (genus Chrysops, family Tabanidae). This morning when I pulled in, ten of these angry beasts landed on the windshield, determined to get to me.
Now, I can appreciate them as well as any other insect. They are beautiful, complex creatures with a vital role in the ecosystem. But there is something maddening about giant buzzing flies which pummel into you at full speed, bouncing off your forehead and crawling in your ears, which could bite you with their steak-knife-like mouthparts at any moment. Especially when there are dozens of them following you around.
Welcome to summer.
There is a big field of milkweed plants near my new apartment.
I went for a walk to investigate the field, and saw that the milkweed beetles (Tetraopes tetrophthalmus) are in abundance. I saw many males mate guarding – holding onto females before or after copulation, I’m not sure which in their case. It can be tough for a female to find another mate when the first guy is still hanging on.
These beetles are interesting for a variety of reasons:
Their antennae bisect their eyes, making it look like they have two eyes on each side.
The beetles will stridulate (made a squeaky scraping sound) when they are handled.
Since they eat milkweed plants, they become distasteful to predators. Their red and black aposematic coloration serves as a warning.
I learned today that milkweed plants are also a popular spot for night pollinating moths, including sphingids (the hawk moths). It has been recommended that I spend some time outside by the milkweed at night to observe moths as they are pollinating. I will probably grab a lawn chair, a glass of wine, and a headlamp and do that the next night it’s not raining.
On monday several of my labmates and our advisor went on a trip to the New York State Museum in Albany NY. Mostly we went there to pick up some bees for our lab’s bee databasing project, but I also wanted to look at their Acronicta specimens and talk to the entomology curators at the museum. It was a quick visit, but very helpful and a lot of fun.
On the way back, our advisor started craning his neck to see the plants on the side of the highway as we were driving. This wouldn’t be so bad, if he wasn’t the one driving. He thought he caught a glimpse of a tree he really needed to feed some of his caterpillars.
So there we were, crawling along in the slow lane, looking for a tree. We pulled over into the breakdown lane once, but there was no tree.
Finally we did stop near the right tree, and he hopped right out with his clippers (always handy, of course) to grab a branch.
To us this seemed fairly normal. Though I wonder what the people in the passing cars thought!
I have been inundated with hatchling caterpillars… ahh, this is how life should be. My favorite part of entomology is catching and caring for the insects themselves. For the past week I have been rearing a few species in the lab, but some of the clutches were so large I had to transfer them to sleeved branches outside. If you keep too many caterpillars together, they are more prone to disease. Last year I lost many caterpillars to something I called the “butt sickness”… we do not know if it was a bacteria or virus, but it caused intestinal issues until they perished. The butt sickness spread through a few dozen of my caterpillars. Poor little guys. I don’t want that to happen again!
Also, feeding caterpillars picked leaves (as opposed to rearing them on living plants) stunts their growth. This has been documented in books and passed along through anecdotes, but I am not sure if it has been systematically studied. I do know that many of my adults emerging now, which I reared last summer in the lab, are much smaller than wild caught specimens. We would prefer to get healthy, normal sized adults for our collection.
Of the caterpillars I am putting outside in netting, some will stay there until they are ready to pupate and I will simply observe them through the netting. I am interested in whether they rest on the upper or under side of the leaf, if they change their habits depending on the time of day, and whether their behaviors change when they change colors.
Others will be removed once they are larger to use in bird predation experiments. I have a meeting with a collaborator from another university tomorrow to get equipment for that.
Here are some of my little darlings. This species is Acronict lobeliae. It goes through several color/pattern changes throughout its life as a caterpillar. This is the second instar.
Here I am moving some caterpillars to their new enclosure outside. I call these my “poodles” because of their fluffy end segments. They are actually Acronicta impleta. You can sort of see them… the black fuzzy specks that are about 4mm long…
Some of the sleeves all set up.
This is my first time rearing caterpillars outside, so I am hoping everything goes smoothly. I have more eggs waiting to hatch, and more eggs are on their way from a collaborator. I am going to be doing much more serious blacklighting this week and next week, hoping to get some more females.