If you hear the phrase “monkey slug”, your first thought is probably not of a caterpillar. But that is indeed the common name for Phobetron pithecium, a caterpillar/moth in the family Limacodidae.
Limacodidae are collectively known as the slug caterpillars due to their reduced legs and slimy looking underbelly. They even crawl by means of a liquified silk trail that they glide effortlessly across. So that is where the “slug” part of the name comes from. But “monkey”? No one is quite sure. The adults are called hag moths, which doesn’t sound very flattering, though they are adorable little moths.
I have never seen one of these caterpillars in the wild, however a friend of mine (Sam Jaffe of The Caterpillar Lab) was kind enough to part with a few of his fuzzy little charges. I have no use for them in my research, but they have been fun pets.
A few more facts:
They can cause allergic reactions in some people (I have not tested myself yet, but just look at those hairs and spines!). However they have glided across my hands with no reaction, so it would probably require rubbing the hairs into your skin.
They do have a head, but it is usually hidden.
They feed on a variety of trees and shrubs, mine are feeding on oak.
The “arms” can come off, the hairs are in fact embedded in a scaffold of some sort of slime that covers the body. This is a feature common to many limacodids.
Here are some photos I took of these guys today.
I mentioned The Caterpillar Lab in an earlier post – earlier this month I finally got to see them in action at a show. I went up to VINS (Vermont Institute of Natural Science) on August 2nd to visit my friend/college roommate Alyssa, as she has been working there for the summer. She was a year ahead of me at McGill, and had just decided to switch to studying entomology when she met me. I love coincidences like that! We became inseparable weird-os who love bugs, working out, and shopping for shoes. Grad school (and life in general) has a way of wrenching people apart, but whenever we’re in the same region of North America we try to visit.
August 2nd was also the date of the Incredible Insect Festival hosted at VINS, featuring The Caterpillar Lab and a whole day of insect themed activities. I couldn’t pass up that opportunity to see parts of my world collide. And I figured it wouldn’t hurt to have another entomologist on hand for an insect festival.
Here is part of the Caterpillar Lab set up – tables decorated with bouquets of plants, each hosting a handful of caterpillars. Most were content to stay on their plants, while others were kept confined to cages (due to a propensity for wandering away). It’s really amazing that people get to see and interact with the caterpillars like this, and with such a huge variety! Yes the large cecropias are cool, but they also have daggers, monkey slugs, prominents, decorator caterpillars… the ones overlooked in more typical outreach programs and museums. There is also an army of dedicated workers/volunteers who keep the show humming.
One really neat feature is their video camera set up – whenever something cool is happening at the tables (there’s always something happening), they can show the live feed on large screens. Could be a caterpillar molting, pupating, feeding, or even with wasp larvae emerging from its body and spinning their cocoons (below).
I got to help with story time, games, and (my favorite), a bug hunt in a meadow. We had an amazing time teaching the kids (and their parents) how to catch butterflies and flies and beetles and ambush bugs (even some caterpillars!), and we had so many stories to tell. We were armed with butterfly nets and vials and field guides, answering questions and catching some insects ourselves.
Overall the festival was a great success. It also included demos on how to make nest boxes for native bees, lectures on pollinators, and other crafts and games. It was encouraging to see so many people attend, and to see such interest and excitement from the children. You never know who might get inspired enough to pursue entomology as a hobby or a career. I know I would have loved a program like this as a kid.
I’m hoping to do more outreach like this, especially through the Connecticut Entomological Society. Probably not this fall, as the semester is about to start (signalling the end of what little sanity I have at the moment), but I’m doing some brainstorming for the spring and next summer. If you have any ideas/suggestions for outreach events around CT, let me know!
There are caterpillars called “slug caterpillars” due to their, well, slug-like appearance. They are the Limacodidae, and they are some of the most beautiful and bizarre caterpillars out there.
Not to be outdone, there are a few species in the genus I’m studying, Acronicta, which resemble the infamous slug caterpillars. Blobby green things that hide their heads while at rest.
These caterpillars were raised from eggs laid by a few females I captured in Boerne, Texas. I am uncertain whether they are Acronicta vinnula (common throughout the eastern US) or Acronicta lepetita (native to southern Texas, and so closely resembles A. vinnula that I am unsure how to tell them apart). As far as I can tell, the caterpillars are identical to the A. vinnula I have raised in the past.
It appears that no-one has raised A. lepetita before. Someone please correct me if I am wrong.
The most information I can find is that “the larvae feed on various plants”. Thanks Wikipedia, that’s quite helpful.
What might be more helpful is a look at the adult. Here is one of the mothers.
My caterpillar season is starting to gain momentum. Caterpillars are hatching, eating, growing, pooping. Getting eggs in the mail from collaborators. Running around campus to collect plants. And some of the caterpillars from my Texas trip are approaching pupation.
I was somewhat in denial of this fact until I saw the size of this guy.
That is a FAT caterpillar! I’d never seen an Acronicta caterpillar look quite so much like it’s going to pop. It also wasn’t in a terribly good mood.
Today I found out why. I checked on Mr. Angry Sausage Caterpillar and it looked a bit… different.
The bright reddish orange coloration and jet-black head were an impressive change. I have only seen this sort of change in one other species, Acronicta lobeliae, which also gains a black head and darker coloration before digging a pupal chamber.
I realized this caterpillar had stopped feeding and was ready to pupate. Poor thing was waiting for the right substrate!
I put a piece of soft, spongy wood into the container, since most Acronicta pupate in wood. It found the wood within minutes, and within an hour had chewed a tunnel into the wood. It’s currently sealed up, where it will remain for a couple months until it is ready to emerge as an adult.
I’m still not entirely sure which species this is. It was collected in Fort Davis, Texas. My guesses are either A. afflicta or A. brumosa. What do you think?
To keep costs down, Ben and I decided to camp for the entirety of our Texas trip (aside from two nights at a colleague’s house). This made our trip feel even more adventurous. We’re used to showing up to a research station with dorms, a kitchen, and a laboratory with supplies. This trip was quite different! We brought my tent, and bought some cheap sleeping pads and sleeping bags at Walmart when we arrived. We also bought some batteries to run our lights, and parts to build a light trap.
We arrived in Dallas, loaded up the car with supplies and food, and drove out to Abilene State Park. I truly did not believe we would fit all of our supplies into a compact rental car, but we did.
The area seemed scrubby, a little dry, and an odd mix of forest, scrub, and almost-desert habitat. The air was hot and humid. There were only a few other people in the campground, as this is not an ideal time to be camping in Texas. As soon as the tent was set up, we set off to explore.
We saw a few caterpillars just by walking around – like this little notodontid.
Our daytime caterpillar search wasn’t terribly fruitful though, so we held out hope for the night. We weren’t too impressed with what the light brought in (our campsite had electricity!), but we did have fun (and strained our necks) looking for caterpillars. We were spooked by a few raccoons, but otherwise didn’t run into any trouble.
Our first big find turned out to be an Acronicta caterpillar! I spotted it sitting on a branch just above my head. I instantly recognized its fuzzy gray body as belonging to Acronicta lobeliae.
But I wasn’t prepared for what happened next. After taking this photo, I reached toward the caterpillar to pick it up. It instinctively dropped to the ground, where it landed directly into an antlion pit! It thrashed around as the antlion tried dragging it under the sand. I quickly scooped up the caterpillar but it appeared paralyzed or dead – frozen into a half curled position.
I kept the poor guy anyway, and within about an hour it was back to normal. Whew!
Here are some other pretty caterpillars we came across:
We weren’t blown away by our first night, but I was quite happy to have an Acronicta caterpillar in hand. We stayed one night, and the next day continued our journey west, to Fort Davis.
Joe Acronicta had had enough of us poking and prodding him, and decided to pupate.
I know that most Acronicta species pupate by tunneling into soft, dead wood. But usually this is a shallow groove, covered by bits of wood and silk. Sometimes they burrow in deeper, but you can see the hole behind them.
Joe decided to be a bit like some other Acronictines (species in different genera, but still closely related to Acronicta). Genera like Comachara, Polygrammate, and Harrisimemna all dig deep tunnels into wood. Then they crawl out and back into the tunnel rear-end first, sealing up the entrance with silk and bits of wood.
That’s exactly what Joe did.
The cleverly disguised entrance.
I’m not sure how long it will be before he emerges, maybe a few weeks or months? When caterpillars pupate early in the season, it usually (but not always) means they will emerge in time to start another brood before cold weather arrives. If they pupate late in the season, they will usually (but not always) overwinter as a pupa.
While we are pretty sure that we have these caterpillars matched up with the correct adult, we are excited to have an adult emerge so we are 100% sure. I’ll post pictures when Joe makes his appearance as a moth!
While at the Smithsonian National Museum of Natural History, (see previous posts here and here) I did manage to tear myself away from the collections long enough to browse some of the public exhibits. I did not go into the butterfly house (didn’t have my wallet with me, you have to pay to enter), but I did see some caterpillars!
There was a whole section of the museum devoted to insects and invertebrates, with many live organisms on display. There were a lot of the usual suspects (mantids, tarantulas, roaches), but they also had some hornworms (Manduca sexta). There was a display with a multitude of pupae, a few caterpillars, and one freshly emerged adult. It was being nibbled by a persistent, and apparently violent, caterpillar. I do not know why.
There was also a display where you could see some pupae of various species hanging – waiting for their chance to emerge and become part of the butterfly house. There were not just butterflies, though. I could see many moth cocoons, the fuzzier looking ones at the bottom.
And I really liked the displays! The blatant emphasis on evolution in almost every single display and description is refreshing (the hall of human origins is wonderful). Whenever I start to despair and worry that there is not hope for humanity to accept science, I should go visit a natural history museum. They don’t hold back.
Now I just need to start planning my next trip back. Hopefully within the next few months! (and maybe I’ll schedule some time to be a tourist)
I have determined that a friend of mine, who works in another lab, has access to materials I could use for inflating caterpillars. I can’t wait until the collecting season starts and I can start on my own specimens.
While some inflated caterpillars are curated within the main collection, and some of them are grouped by family in the larval cabinets, there are many “miscellaneous” drawers with arrangements like this.
All sorts of caterpillars! The nice green color of the swallowtail caterpillars (bottom right-ish) was not preserved though. This seems to be one limitation of caterpillar inflation – patterns remain, but colors become lost or distorted. Most inflated caterpillars are some shade of tan/brown. This could be due to the heating process or simply by fading over time due to light exposure.
One thing I did not expect to see – everted osmeterium! Swallowtail caterpillars (Papilio) have an eversible gland called the osmeterium which is normally held inside the body. When threatened, the caterpillar sticks out the two forks and tries to touch the attacker – wiping them with smelly defensive chemicals. Just the smell could be enough to deter a would-be predator, but I’m sure the taste is pretty bad too.
Many of the geometrid caterpillars were preserved in their usual hunched position. I wonder if this was induced somehow during the heating process, or if they simply inflated into the most natural position?
I couldn’t help but include a photo of the megalopygids (fuzzy guys on the right). Preserving them must have been a delicate task, hopefully carried out with gloves – they can give quite a vicious sting! They look more like little mice than insects, and each hair can leave a welt on your skin. I was tempted to test whether old preserved specimens would still sting, but decided not to try.
Have any of you ever inflated a caterpillar specimen before? If yes, do you have any advice?
One of the great things about being an entomology graduate student is that going behind the scenes at natural history museums is not only a perk – it is virtually required. Visiting a museum collection means new professional contacts, new collaborations and inspiration, examining specimens, and sometimes borrowing specimens to study at home.
Last week, during “spring break” (grad students might get breaks from classes, but never a real break from work) some members of our lab took a trip to the Smithsonian National Museum of Natural History. We drove from CT to DC, stayed overnight at a cheap hotel, and spent the next two days frolicking amongst the insect cabinets. Well, maybe I was the only one frolicking.
Plenty of room to frolic. Carefully.
I actually only spent about an hour, on the second day, exploring the public exhibitions. It was much more fun being behind the scenes, especially with the vast amount of specimens available to explore.
The Smithsonian NMNH holds over 35 million insect specimens in drawers, vials of alcohol, and slides – making it one of the largest insect collections in the world. You can read about the History of the United States Entomology Collections here.
I went to the museum with one major purpose – to see which caterpillars in the genus Acronicta they have preserved in alcohol, and if there are any species I have not yet examined and could borrow for further morphological study. Caterpillars are not often kept in collections (at least not in the same numbers as the more popular adult butterflies and moths) but luckily, the NMNH had what I was looking for.
There were 24 jars of ethanol holding Acronicta caterpillars, each jar containing up to a few dozen small vials with preserved specimens. I looked at every single vial, feeling the familiarity of old friends and the excitement of species I had not yet seen. Some specimens were collected by the authors of a seminal work on Acronicta published in 1898, Smith and Dyar. How cool is it to examine specimens collected by your heroes? I was amazed by the dates on some specimen labels – the oldest I found was collected in 1886.
This caterpillar is 127 years old.
With a spot to sit and look at specimens, the first day absolutely flew by. The entire evening of dinner and sight-seeing in DC felt like wasted time – I wished I could have stayed at the collection. Maybe if I had curled up to sleep under a desk, no one would have noticed?
Science is happening here.
The caterpillars were not just in jars, though. There were also a few drawers of inflated Acronicta larvae from around the world. I took lots of photos, but the memory card from my good camera is currently misbehaving. Hopefully I can recover the photos, though I could always retake the photos on another visit.
Some of the inflated Acronicta caterpillars.
I also met some wonderful people at the museum, and caught up with colleagues I have not seen for months or years. We had some great conversations about field collecting and project ideas. I learned a lot about collecting cave insects while walking through mountains of bat guano – did you know that rabies can be spread through the air? Sometimes entomology can be quite hazardous.
At one point I noticed a toy caterpillar on a shelf in the work room, and gushed over its accuracy and adorable-ness. Later in the day when I returned to my work station, I noticed it sitting on my laptop. My lab members told me I was given a new friend!
Cerura vinula, the puss-moth caterpillar, family Notodontidae. It now happily lives in my office.
The second day was as wonderful and short-lived as the first. I took many more photos of inflated caterpillars, which I will detail in another post. I felt so honored to be allowed to visit and explore such a historic institution, and hopefully will have many more visits over the course of my career.
There are several ways to preserve caterpillars for study. You can boil them and drop them into a jar of alcohol, you can freeze dry them, or you can inflate them.
The photos in this post are all of inflated caterpillars, in the genus Acronicta, found at the Cornell University Insect Collection (CUIC).
Inflating (or “blowing”) caterpillars is a traditional technique that is no longer taught or commonly used, however it can produce fabulous results. The caterpillar remains dry and can be kept in a drawer along with adults, which makes them easier to study than specimens in alcohol. Their external features are usually well maintained – specimens from the early 1900s don’t look much different from modern specimens.
However they are lacking their internal organs, and the last couple of segments are destroyed in the preparation process. The technique is also quite labor intensive and requires unusual equipment. So how does it work?
I have talked to a few entomologists who have inflated caterpillars, but not since their undergraduate or graduate school days. I have found a few resources which describe the process. Here is a description from the University of Minnesota Agricultural Experiment Station:
Basically you cut a slit into the posterior end of the caterpillar, and using a pencil, roll out the guts (starting at the head end). You must be careful to not destroy the hairs and other features of the exterior. Then you insert a glass tube and inflate the caterpillar, and keep the caterpillar inflated as you heat it in a small make-shift oven. One colleague described using a coffee can over a bunsen burner for this purpose.
Once the caterpillar is dry, the glass tube is removed and the caterpillar can be prepared for pinning. Either a wire or stick can be inserted, or the caterpillar can be glued onto the wire or stick by its prolegs underneath the body.
A box of Acronicta americana adults, caterpillars, and pupae
Late (above) and early (below) instars of Acronicta morula
Another benefit of inflating caterpillars is that the body shapes are extended and not distorted by being kept in a liquid. The important bumps and hair positions are kept as their were in life. However the body may be a bit overextended depending on how well it was squished and inflated.
One reason I particularly enjoy the inflated caterpillars is that they are easy to transport and trade – so there are many European species in collections here in the USA. Caterpillars are not often kept in collections to begin with, so to have these specimens available to me for study is quite exciting.
As you can probably guess, I’m going to set up my very own caterpillar inflating oven as soon as I can! And I’ll have another post soon on even more inflated caterpillars I have found at other collections.
University of Minnesota, 1908. 16th Annual Report of the Agricultural Experiment Station. Bulletin #105. How to Collect and Preserve Insects. Pages 119-146.