Monthly Archives: June 2012
I am so excited!!!
I just purchased a custom order from CaterpillarArts on Etsy. She opened up her shop a week ago, featuring beautiful little caterpillar pendants. When I saw her work I had to ask for my favorite species, Acronicta funeralis. I know it’s a tricky one, but AJ blew me away with how accurately she was able to re-create this caterpillar.
I can’t wait to get this little guy in the mail next week!
For comparison, here is a photo I took of a real Acronicta funeralis last summer:
Please check out her shop, more goodies are being added frequently – I just saw she has a few crystalids as well!
Word of the day: Hypognathous
Here is a story about a rather desperate moth.
I have a number of female moths in the lab which I am hoping to get eggs out of. As I checked them today, I realized one of my Acronicta americana was actually a male. Not sure what to do with him, I put him on my friend’s shirt to hang out a while before being released.
Back in my office a few minutes later, I heard a yelp from the lab. I walked over to see the moth climbing on my friend’s beard, probing him with its proboscis. Then it went straight for his mouth!
Moths and butterflies have a behavior called “puddling”. Males (some females do this as well) will suck up liquids to gain nutrients such as sodium. Butterflies and moths can be observed puddling around puddles, ponds, mud, dung, damp concrete… and apparently, some are also attracted to saliva. Males are the usual suspects because they will offer these extra nutrients to females as a sort of nuptial gift along with their spermatophore during mating.
This moth was fed sugar water while in his enclosure, but apparently the allure of sweat and saliva were too much to resist.
Here is a video, to show just how excited this moth was:
I wonder if other moth species would lap up human saliva so eagerly? I am not sure anyone in the lab is going to jump up and volunteer for that study.
This is how I spent my Saturday: No baby leave the socks on, Crossfit throwdown.
Don’t know the results yet, I suspect I was in the middle of the pack.
It was a long day of blisters, bruises, sore muscles, sun burn, and fun!
Not every day can be spent in the lab or in the field.
What do you do to loosen up after a hard day/week of science?
Word of the day: Sericulture
(Who am I kidding, these words aren’t random. I pick words that relate to Lepidoptera – from the Torre-Bueno Glossary of Entomology)
Sericulture, commercial raising of silkworms, Bombyx mori, for their silk.
There are many direct and indirect ways that insects benefit our lives. Silk is one of them – that amazingly textured fabric is the product of the domesticated “silkworm”, not a worm but a caterpillar. Sericulture refers to how the caterpillars are raised and farmed for their silk.
Why do caterpillars produce silk, anyway? And how?
Caterpillars have a pair of spinnerets behind their mandibles, which are connected to silk glands. Caterpillars produce silk for a variety of reasons – safety lines, shelters, ballooning, molting mats, cocoons, decorating themselves, and probably more! If you ever see a caterpillar suspended in mid air, it is connected to the tree above from a line of silk. If you watch carefully, you might observe it rolling the silk into a little ball as it pulls itself back up. Some caterpillars will lay down silk wherever they go, so they will never drop too far from their host plant.
When caterpillars are in their first couple of instars and quite small, they may use silk for ballooning. Spiders do this too – releasing some silk fibers into the wind, they can be blown to a new locality. This is helpful if you have a hundred hungry siblings to compete with.
Shelters can be made by silking together two leaves. Molting mats are a layer of silk that a caterpillar can hook its crochets into in order to pull out of its old skin. Cocoons are an enclosure made by some moths to protect their pupa, often made of silk and hairs. And some caterpillars will try to blend in by attaching bits of plant matter to their bodies with silk.
Humans have been taking advantage of the silk production of B. mori for about 5,000 years now. Interestingly, the species no longer exists in the wild, and is perpetuated only for the silk trade and for scientific research. The silk is obtained from the cocoon, which is made of one long strand. The pupa is then discarded or eaten. Yum!
Here is an awesome blog with pictures illustrating the whole process.
Word of the day: Tubercle
(Who am I kidding, these words aren’t random. I pick words that relate to Lepidoptera – from the Torre-Bueno Glossary of Entomology)
Tubercle, a small knoblike or rounded protuberance… in caterpillars, body structures, sometimes bearing setae, e.g., pinaculum, verruca.
Bonus word! Tuberculiform, shaped like a pimple or tubercle.
Caterpillars usually aren’t just hairy all over – the primary and secondary hairs, or setae, are arranged in an organized fashion that is mostly conserved throughout Lepidoptera. Chaetotaxy, or the arrangement of setae, can be important for distinguishing between families or even species. The length of hairs and their relative positions to each other may seem subtle, but can have important phylogenetic implications.
The hairs are all named based on their position on the body; we currently use a system devised by Hinton (1946). For example there are usually two hairs toward the dorsal (upper) side of the segment, so they are called D1 and D2. These may arise from a small or unnoticeable protrusion, to a large conspicuous wart. This is where terminology gets tricky. Many scientists have their own preferred names for these structures, and their own cut-off points for when to use which word. They are usually describing the same structure, it is just a matter of how large it is. In our lab we tend to use pinaculum for a small one, tubercle for medium, and wart for large. When in doubt, you can call it a tubercle.
Here is an example of a small one, in an SEM image I took of a setae (Sympistis species).
Word of the day: Frass
(The word of the day is a random word on a random page of the Torre-Bueno Glossary of Entomology)
Frass, solid larval insect excrement; plant fragments made by a wood-boring insect, usually mixed with excrement.
We deal with a lot of frass around here.
Caterpillars are eating machines… which means they are also pooping machines.
I just realized I don’t have any good photos of frass, but here you can see the pile left behind by some Acronicta americana caterpillars.
Luckily for us, caterpillar frass is usually fairly innocuous – it is dry, doesn’t smell, and is composed of vegetative matter. Kind of like my rabbit’s droppings. Unfortunately, unlike my rabbit, caterpillars cannot be litter trained. So we spend lots of time cleaning out our rearing containers.
Some other frass stories:
While cleaning the lab sometime last year, we came across a frass collection. No joke. Little tiny boxes (perhaps meant to hold rings or earrings) were opened up to reveal giant pieces of frass from saturniid caterpillars, ziploc baggies full of frass, boxes of frass that rattled like maracas. I’m not sure if we got a real explanation as to whose they were or why they were collected… or where they disappeared to after we found them.
And did you know that some caterpillars fling their frass? It sounds silly at first but it makes sense. Some parasitoids (like wasps) will find their prey by following the scent of frass. So if you ditch the frass, you are ditching the evidence of your presence.
Some caterpillars will grab it and throw it. Some can really fling it far, while others give more half-hearted attempts. Like this little Acronicta afflicta I filmed last year.
Another way, that requires less effort, is to fling the frass with a built-in anal comb. Let me tell you, I was afraid to google that. Here is a picture (from omafra.gov):
Basically those spines are used to eject the frass at high speed. I will try to get videos of this if we raise any frass-flingers in the lab this summer. I remember last year we had a heck of a time cleaning some caterpillar containers because the sides were coated in frass, instead of it just dropping to the bottom.
Some lab hilarity from last year:
Speaking of frass, I have some caterpillars to attend to.
How to defend yourself
… against fresh fruit.
No, wait a minute. Pointed sticks? No, not that either…
Caterpillars have a variety of methods for defending themselves. When you are a soft squishy tube of yumminess that everything wants to eat, you need to take precautions. As a caterpillar you can be distasteful or toxic, hide with cryptic coloration, or adorn yourself with spines. But you do not have to be passive.
We have seen other caterpillars with nasty big pointy teeth (I’ve been watching too much Monty Python lately, can you tell?) here.
This is a caterpillar I came across doing my field work the other day. It is Hyperaeschra georgica, in the family Notodontidae. I noticed it twitching once I approached. And when I poked at it… well, see for yourself:
I bet that would freak out most birds or predatory insects! It always startles me a little bit when a caterpillar “attacks”, even though I know they cannot really hurt me. Well, some of them do have sharp mandibles and can give a good pinch.
I have also experienced the “look at my warning coloration, don’t eat me if you know what’s good for you” dance of another caterpillar, Phyllodesma americana, in the family Lasiocampidae. The lighting wasn’t very good in the lab, the pale patches on its underside are actually orange. Many insects use the combination of orange and black to warn predators about their distastefulness.
We will try to get a better video of this guy in action soon.
Have you seen any other caterpillar defense displays in the wild or in the lab? What is the strangest thing you have ever seen a caterpillar do? I was just reminded of this caterpillar I saw in Ecuador last year. When I came close, it contorted itself into a strange pose. Hmm.
I’ve been looking for you
I was really hoping to get Acronicta hasta eggs this summer. I missed the first brood, but there should be another round of mating/egg laying this summer. That’s the nice thing about Acronicta, most of them have two broods per year. It’s a nice safety net if I mess up the early spring window for collecting.
Two weeks ago we came across this big guy… Acronicta hasta. There is no way this species should be in its final instar already! The female must have emerged in April when we had some of those crazy warm days… and somehow the caterpillars managed to survive a long stretch of cold nights with only a little vegetation starting to grow.This might explain why some species were hard to get this spring – the strange weather threw off a lot of insect life cycles.
The early instars are all green with a red stripe down their back. They sit on the upper surface of leaves, flaunting themselves to birds. It is not know if they are chemically defended, or if the red stripe serves as aposematic warning coloration. They feed on cherry, which is not exactly a poisonous plant. This is why I would love to experiment with them! A study by Singer et al. (in press) has shown that birds tend to leave this species alone.
The last instar, however, is black with yellow spots and a maroon red stripe down its back. It prefers to rest on twigs or bark, as seen in this photo (this was its natural resting position when we found it):
And here it is in the sunlight:
Since this species burrows into wood to pupate, it makes sense that they would don a darker appearance – you probably do not want to be a bright green caterpillar on bark. If they are really only bluffing with their red warning stripe, it would be a good idea to try hiding some of the time.
“Poke nature” is a phrase taught to me by one of my professors at McGill, and a philosophy I have lived by my whole life. Not everyone may agree with it (many environmentalists think we should leave nature alone completely), but I believe that interacting with nature is one of the best ways to learn about it. Keeping something in captivity for a little while, or photographing it, can bring behaviors to light you wouldn’t otherwise observe. I have been greatly inspired by watching and poking at the Acronicta caterpillars I am studying.
Here are a few shots of cute creatures we came across at Hurd State Park. Of course I had to scoop them up.
We think this little caterpillar might be an Acronicta species. It was probably in its first instar.
I spotted this elaterid beetle in flight while we were eating lunch. I could tell it was an elaterid (click beetle) by the way it held its elytra while flying. It wasn’t until it landed that I realized how large it was – it was an eyed elater (Alaus oculatus)! I had never seen one in the northeast before, only in Texas and Arizona. It turns out this species would prefer to play dead, as opposed to clicking to right itself. It clicked once (only got a couple inches into the air) and then decided to sit still for the next hour.
Not an insect, but still awesome. A grumpy little american toad (Bufo americanus). It peed on me.
Over the years I have gotten better at controlling my “must catch it” instincts in order to make observations of natural behavior. And I have learned that it isn’t always worth it to catch a snake and smell like musk for the rest of the day. But there is a reason I don’t take up bird watching as a hobby – it’s no fun (to me) if you can’t catch the birds to get a closer look.
I have learned that toads will pee if you pick them up, frogs can scream like a baby, slug slime is almost impossible to get off your hands, different species of snakes have different strategies for musking, great spangled fritillaries are one of the hardest butterflies to catch, ambush bugs can bite hard, click beetles only click as a last resort, some caterpillars will fall off a leaf on purpose while others will cling tightly, wolf spiders are gentle and can be loving mothers, snapping turtles smell gross, giant water bugs will eat goldfish… you get the idea.
What have you learned from bothering nature?