Do you know the insect species that inhabit your backyard? What about a local park or nature preserve? How about your county? These are important questions to think about. If no one knows the animal diversity in their area, then why would they stop to think about protecting that diversity? Some of the most interesting animals are very specialized and need certain habitats to thrive; without those habitats, they'll disappear. I think we can all agree that nature is important, and having a knowledge of your local species (of insects, mammals, birds, plants, fungi...) is empowering. You can see ecological connections and gain a new-found respect for your fellow organisms, just from being able to identify species and know what's around you.
A Luna Moth (Actias luna) soon after emerging from the ground. Its wings aren't yet ready to fly--you can see how small they are.
With this topic in mind, I've been working for the past few months on gathering together pictures and information about arthropod species that occur at the Barbara A. Beiser Field Station (BBFS) near Marietta, Ohio. As I've written about before (here and here and in an article for the Marietta Natural History Society newsletter here [PDF]), I conducted a lot of my undergraduate research at the BBFS and found many species. I never quite had the time to identify and write down all the species I found while I was an undergraduate, so I put it off for a while.
Until now.
An Ichneumon wasp, Megarhyssa macrurus, drilling into a dead tree to parasitize a wasp larva.
After months of identification, I've completed the project! (I'm looking for a good way to put this list online.) This is the first biotic index (list) of species from the BBFS, and focuses only on arthropods (it will be expanded to plants and other groups in the future). All in all, I identified 181 species including insects, arachnids, and millipedes/centipedes. This is nowhere near a complete list, but it's a start. I only included arthropods whose identifications I was sure about, so I left out a few species I was unsure of, falling just short of my 200 species goal. But that's okay--the list isn't useful unless it's accurate, after all!
A pair of Euryurus leachii millipedes under UV light. Usually found in decaying logs, these millipedes fluoresce a pretty bluish-green color.
I gained a lot of experience with local insects while working on this project and feel pretty confident about being able to identify many of the insects in Washington County. I now have a much greater knowledge base about insect taxonomy and what a "species" really means. When it comes down to it, a species is someone's hypothesis, and sometimes the hypothesis isn't accepted by everyone. It can be based on tiny characteristics that are a real pain to hash out, especially when you're trying to identify an insect in a group that's not well-studied!
What did I learn after putting together this list? Most importantly, I learned that I still enjoy taxonomy after hours and hours of (sometimes frustrating) work. I also learned that we have some astounding arthropods at the BBFS, and in the county. Throughout this post I've included pictures of arthropods I found there that I never knew about before, with life histories that are seriously interesting and unfortunately too long to include in this post. There's a diversity of life in southeast Ohio I never would have known about before undertaking the research I've done and I'm lucky to have had that opportunity. It's taught me that you don't have to go to the rainforest to find beautiful and interesting animals; sometimes the forests of southeast Ohio can beat out the rainforest!
A male Marbled Orbweaver, Araneus marmoreus. This spider has many color forms, of which the black and yellow form is especially striking.
I hope to use my experience to encourage others to take a second look at the critters in the area and to truly take pride in them. Why not say "These things are astounding!" and put these animals on a pedestal? Arthropods like the Luna Moth, the Ichneumon Wasp, our UV-fluorescent millipedes, the Locust Borers, the Wheel Bugs: these "bugs" are crazy awesome and should be celebrated!
The Spicebush Swallowtail caterpillar, Papilio troilus. This unique caterpillar changes throughout its life stages--young caterpillars look like bird poop, while older ones (like this one) mimic snakes!
In order to accomplish this goal, I'm working on completing another biotic index--this time for Washington County, with some input from surrounding counties. I want to adapt this larger biotic index into a field guide to arthropods in the area, with pictures and information about each species. It will introduce people to these bugs and save them some time in trying to identify them. Essentially, I want everyone to have the same pride in our many-legged fauna as I do.
Narceus americanus, the gentle giant. This is the largest millipede in our area and eats dead leaves. Interestingly, it sometimes scales trees.
It doesn't help anyone appreciate our arthropods if I keep my knowledge locked up in my head, so I need to spread it! I have no idea about how long this project will take, nor when it will be done, but it hopefully won't take more than a few years max. If you can help out in any way, please contact me!
I've always had an interest in history and still enjoy it, though my main focus has shifted to natural history. Over the past few years I've discovered the richness of southeast Ohio's history. There's a rock etched with George Washington's initials in my hometown, mounds built by Native Americans are scattered throughout the area, and the first towns established in the Northwest Territory are in southeast Ohio--the first was Marietta in 1788.
It was during this research that I came across a true Renaissance Man: Samuel Prescott Hildreth. He was a doctor that lived in Marietta during the 1800s, but he also dabbled in history, politics, geology, natural history, and more. I've previously written about Hildreth here after finding a notebook of insect notes he wrote (with illustrations), and it's his writings on natural history that interest me most.
Hildreth's natural history research was particularly helpful to researchers of North America's periodical cicadas, which are classified in the genus Magicicada. His observations of the 1812 and 1829 periodical cicada emergence events were the first detailed and accurate reports of the cicadas' 17 year life cycle. Those reports, along with his verification of the 1795 emergence, provided the documentation to confirm the periodical cicadas' unique habit of emerging en masse every 17 years.
A snapshot of a more recent emergence: a 4-year acceleration of Brood V in Marietta, OH; May 2012.
I first learned about Dr. Hildreth's work in Dr. Gene Kritsky's book: In Ohio's Backyard: Periodical Cicadas, published by the Ohio Biological Survey in 1999 and available for order here. The book is a great resource and has an extensive bibliography, which has aided my research on Hildreth considerably. The last time Dr. Hildreth published a scientific paper was during the 1800s, so his papers aren't exactly easy to find. Thankfully, today we have the Internet and libraries that digitize their collections.
As I conducted research over the past few weeks (by both searching online and visiting libraries), I came across four papers published by Dr. Hildreth about periodical cicadas. I could have missed a few, as I wasn't able to find those published in German or French publications, but the ones I found seem to be the main four which are referenced in other publications. In these, he writes about the life cycle of the cicadas and their effects on the area's wildlife (including humans).
His first paper, Notes on certain parts of the state of Ohio, published in 1826, details the periodical cicada emergence of 1812 with the notes he wrote in his journal at the time. His journal notes describe the cicada emergence in late May until the cicadas are gone, by the end of June. He confirms the 1795 emergence in this paper.
Hildreth's next publication came out in 1830, entitled Notices and observations on the American cicada, or locust. This was his first paper focused solely on the periodical cicada Magicicada septendecim, known then as Cicada septemdecim. This is the most eye-catching publication of the batch, as it opens with a plate of illustrated cicadas.
Hildreth's cicada plate from Notices and observations on the American cicada, or locust, published in the American Journal of Science and Arts, 1830. Notice the watermark--Google Books helped me out here.
Hildreth begins his five page paper with a bold (and very true!) statement:
"No part of natural history more abounds in wonderful and
extraordinary productions, than that portion of it embraced in the study
of Entomology."
The paper goes on to cover the 1829 emergence that occurred during the previous
summer and gives an overview of the periodical cicada's natural
history. Hildreth mentions a "smaller form" of cicada in this paper--the first account of the species Magicicada cassini, formally described by J.C. Fisher in 1851.
Hildreth regales the reader with stories of how the local wildlife responds to the sudden buffet: by taking advantage of it like there's no tomorrow. Hogs, birds, squirrels, etc. "fatten on them," and birds are so focused on the cicadas that they don't even bother to eat the cherries in Hildreth's garden! Interestingly enough, some people even used the cicadas to make soap, taking advantage of the fact that the cicadas are "plump and full of oily juices." Maybe that was a kind of revenge against the creatures, as the males could be heard singing from morning until night and be heard from a mile away. I personally love the sounds they make, but not everyone feels that way. If you've never heard them before, skip to 1:39 in the video embedded below and Sir David Attenborough will help you out.
In 1847, Hildreth published two more papers: one included topics other than cicadas, such as a meteorological journal he kept in Marietta during 1846. The second article was a shorter reprint of the first, including only the pages about the periodical cicada. These articles document the periodical cicada emergence of 1846, making it the fourth emergence Dr. Hildreth wrote about: not too shabby!
Adult Magicicada septendecim
After spending many hours looking for old references just to learn about a bug, I appreciate historians a bit more now. I also have even more love for libraries. The Marietta College Legacy Library's Special Collections department in particular was very helpful during my search, and is the reason I found Hildreth's A Portfolio of Insects that I wrote about previously. Washington County's Local History and Genealogy Archives was also a great resource. Since neither of those libraries had these papers by Hildreth, I sent them copies for their collections, just in case anyone else in the area wants to learn more about Hildreth's work. There's no sense in keeping them locked up in my computer, after all.
You can expect more posts about Dr. Hildreth in the future--he wrote about much more than just periodical cicadas. I'm finding out more and more about his life; he was a very interesting guy.
I encourage you to do some research into your local history as well! You never know what you'll find. Maybe there was a person similar to Dr. Hildreth in your town.
For those of you who don't live near Marietta, Ohio, I've uploaded all four documents to Google Drive and they can be downloaded at this link. They're a great look into the scientific writing of the past, and Hildreth's writing is surprisingly readable. References: Hildreth, Samuel Prescott. 1826. Notes on certain parts of the state of Ohio. American Journal of Science and Arts. 10: 152-162; 319-331. Hildreth, Samuel Prescott. 1830. Notices and observations on the American cicada, or locust. American Journal of Science and Arts. 18: 46-50. Hildreth, Samuel Prescott. 1847. Abstract of a Meteorological Journal, for the year 1846, kept at Marietta, Ohio, Lat. 39° 25' N., and Long. 4° 28' W. of Washington City. American Journal of Science and Arts. 3: 212-222. Hildreth, Samuel Prescott. 1847. On the habits of Cicada septendecim. Annals and Magazine of Natural History. 20: 136-141. Kritsky, Gene. 1999. In Ohio's Backyard: Periodical Cicadas. Ohio Biological Survey Backyard Series No. 2. Columbus, Ohio. vi + 83 pp. [ISBN: 0-86727-132-9]
I had some extra time after work today, which I used to visit Marietta College's Special Collections. They keep scores of old documents, many dating back to when the Ohio Company of Associates first established Marietta in 1788 as the first settlement in the Northwest Territory. What I was after today, however, had an Entomological bent to it.
Samuel Prescott Hildreth, a doctor who lived in Marietta during the early to mid-1800s did some of the first work in Ohio studying insects. He was a naturalist and published the first observations of the periodical cicada's 17 year life cycle, which is what I was after. I didn't find any of his cicada papers, but the librarian did bring me a book he wrote and illustrated, entitled "Portfolio of Insects."
This book includes paintings by Hildreth of various insects from Marietta and elsewhere in Ohio. When I first opened the book, I was greeted with beautiful illustrations of the tobacco hornworm (Manduca sexta) during all of its life stages. I had an immediate visceral reaction to that page--the tobacco hornworm is one of the first insects I raised when I became interested in Entomology, and it was emotional for me to be confronted by this right after opening the book. It was a direct connection to a naturalist who had written this Portfolio 150 years ago.
That caught me by surprise. I was excited, but sheesh, that almost brought tears to my eyes.
I soldiered on, invigorated by each page and by the connection I felt with Hildreth. His book was a veritable menagerie of the most charismatic insects you can find around Marietta, and which are still around today--one of the perks of having a lot of woods and natural areas in the county.
The book is only about 40 pages long, and each page showcases a colorful new creature: a brilliant Luna moth, a royal walnut moth, a smattering of other large moths and butterflies, a giant water bug...even a red eft (Notophthalmus viridescens) and a sketch of what Marietta College looked like during his time! As for his handwriting, it was difficult to read. I could make out some descriptions and names of plants and insects, but that was about it. Fortunately, his labels for each illustration were neater. I recognized the scientific names for each species and even noted some that had changed during the previous 150 years. Imagine that, eh?
Hildreth was truly a Renaissance man: in addition to being a naturalist, he was a doctor, geologist, and historian. He was active in the community as well, and today has a street in Marietta named after him.
Sadly, I only had an hour to look at the book before I had to leave, but I'll definitely return soon. I have some more research to do vis–à–vis Hildreth's cicada research, which I hope will also feature some of his illustrations.
Hildreth's Portfolio of Insects is an achingly beautiful direct connection to the past. It means a lot to me, being a native to Marietta, and for me, it inspires a timeless feeling of camaraderie with Dr. Hildreth. I recognize these insects drawn so long ago and I can still go out and find them. Had we lived at the same time, I think he and I would be good friends.
I wish I had at least one picture from the book, but I'll have to speak with the librarian about any effects taking pictures would have on it. Who knows, maybe we can get it digitized. In lieu of any pictures, I will leave you with a quotation Hildreth used to begin a paper on cicadas he published in 1830:
"No part of natural history more abounds in wonderful and extraordinary productions, than that portion of it embraced in the study of Entomology."
I've been busy lately, in a good way. My current project is identifying all the species of insects, spiders, millipedes, and other arthropods I've found at the Barbara A. Beiser Field Station (BBFS) over the past few years as an undergraduate at Marietta College. I spent many hours at the field station and thoroughly explored much of it, taking many photos along the way. I have an article about my experiences coming up in the next issue of the Marietta Natural History Society's newsletter, which I'll link to when it comes out.
UPDATE!: You can read my article here (PDF warning). It starts on page 4, titled Beiser Browsings.
So far I've identified around 200 arthropods from BBFS. The timeline for my sightings and collections goes back to 2010 or so, when I first started going there for things like labs and work days, and the identifications have been a long time in coming. It feels great to have so many identified though, as there hasn't been a taxonomic inventory of BBFS since it was acquired in 2008.
I expect the final list of creepy crawlies to hover around 220, after accounting for duplicates. Some of them are only identified down to family, but I've identified the majority down to species, including some lesser-known groups (that is, those that lack readily-available identification resources) such as harvestmen and millipedes. I've collected many of the species, which are now in the Biology department's insect collection. I'm hoping that somewhere down the line, these collections will come in handy for future students, especially my assassin bug and millipede specimens.
I've found so many charismatic species that have blown me away at BBFS. Combined with the recently-planted patch of pawpaws at BBFS, I expect people to start flocking there in droves in the coming years.
A harvestman from BBFS, Vonones sayi. This pretty species lives under rocks and bark, and exhibits some of the diversity within the harvestmen: they're not all nondescript balls with legs!
It's been a few weeks since I had my last real post, so I wanted to update about that (and brag a little).
I graduated yesterday! I'm now a degree holder from Marietta College and am headed into the real world. (That's my roommate in the picture with me, by the way.) I will be working as an Americorps*VISTA with a local environmental organization, which I'm absolutely stoked about. I'll be able to continue my insect research while with them, so I have a feeling things will work out fine.
I'm working on a few new posts about millipedes and also some neat stuff about periodical cicadas, so I'll try to get back into my regular posting schedule ASAP. It should be easier now that final exams are done!
This past summer, as I mentioned a few times before on this blog, I had the opportunity to carry out a field survey for assassin bugs at the Barbara A. Beiser Field Station. This field station is used by the biology classes at Marietta College for lab sections, such as Zoology and Aquatic Biology.
I knew that I would have a good portion of free time during the summer, and I wanted to get a head start on my capstone project, and do some more research with insects. Out of that grew a project during which I would research the abundance, diversity, and ecology of assassin bugs (insects in the family Reduviidae). I wrote up an application for an Investigate Studies Grant for these types of student-led projects from the college, and I received one to carry it out.
It took place during six weeks in May and June, and I found a lot of different species--both assassin bugs and other insects. I focused on the assassin bugs most of the time, and presented on my findings (I'll elaborate on that in another blog post, but I found 7 different species of assassin bugs) in October. Since then, I've been focusing on all the other insects I found during the project. In order to save time and keep focused, I didn't collect every insect I found, but I did try to snap some pictures whenever I found something I hadn't seen before.
Like this, for example. A scarab beetle, the Emerald Euphoria - Euphoria fulgida.
Fast forward to this past week, and I've been focusing on identifying all the insects and other arthropods I saw. Assisting me with that has been Project Noah, an amazing website that anyone can submit their pictures of wildlife to, upload them to a map, and essentially crowdsource nature with others. (It will receive its own blog post in the future.) I just finished uploading all my pictures from my Investigative Studies Grant project, which gave me a lot of time to reflect on everything I encountered.
It also gave me a number: 137 separate species of insects, plants, spiders, fungi, slime molds, and miscellaneous other groups of life just from those 6 weeks.
That's not too shabby, if I do say so myself. Since it's the time of year to write reflections, I figured that now is as good a time as any to briefly highlight some of my favorite photographs and organisms I encountered. I'll limit myself to five to keep the length of this post reasonable.
This was the first insect I encountered--right on the gate leading to the field station. Unbeknownst to me at the time, I would be seeing A LOT of soldier beetles (family Cantharidae). This particular one is Podabrus tomentosus, which I didn't see many of in the interior of the forest. You know what I did see a lot of? Firefly mimics. Firefly mimics EVERYWHERE. It wasn't even until I was reviewing my photos that I even figured out that most of what I thought were fireflies were actually soldier beetles in disguise. That being said, that is some amazing mimicry. (Consider that paragraph a cliff hanger, I'll cover these mimics in another post.)
Serendipity is better than skill! I got lucky on my first day at the field station and stumbled upon (literally, I almost stepped on it!) a luna moth (Actias luna) that had just emerged from its pupal stage and was crawling along in the grass. Adult luna moths only live for a week and do not only: they only live to reproduce. I had never encountered a luna moth before, so I was excited out of my mind when I found this male (notice how large the antennae are, that's how you can tell the difference between males and females). Not wanting to step on him, I picked him up and placed him on a tree so that he could pump up his wings in peace. I returned every so often over the course of three hours to watch and it was just a beautiful sight. It's a real privilege that we have such a majestic moth in Ohio.
This is the Orange-patched Smoky Moth (Pyromorpha dimidiata), a rare case in which the common name describes the organism extremely well. At first glance you might be reminded of a net-winged beetle in the family Lycidae. It's suspected that this moth is a mimic of those beetles (check out the genus Calopteron for comparison), but may also have its own chemical defenses. Due to this, the mimicry exhibited by this moth and the net-winged beetle is characterized as Müllerian mimicry.
Since both species are toxic and have similar aposematic (fancy word for bright warning color) patterns, the mimicry works to the advantage of both organisms: predators leave them alone since they're distasteful. This is opposed to Batesian mimicry, in which a model toxic species is imitated by other non-toxic species, which obtain the same benefits without needing to be toxic themselves. It's the insect equivalent of putting your purchase on someone else's tab. For more information about this species, you can check out Ted Macrae's entry at Beetles in the Bush.
Next up is a beautiful firefly I found crawling on a decaying log.
Or is it?
Fireflies must be awesome beetles to mimic: even the click beetles (family Elateridae) are getting in on the action! Here we have Denticollis denticornis. Sorry, no common name here, but for simplicity we can refer to it as the firefly mimic click beetle. I mistook it for a firefly when I first saw it, but upon closer inspection, the flared pronotum that fails to cover the head gives it away as a click beetle. Simply a beautiful specimen, I wish I had taken the time to get some more pictures and see where it was going. Now, which mimicry would this click beetle be exhibiting: Müllerian or Batesian? For a nice discussion about mimicry's benefit to this species, check out this link to BugGuide.
Finally, we come to one of my favorite beetles: the pleasing fungus beetle Megalodacne heros. It's in the family Erotylidae and looks as if it should be coming out around Halloween. Unfortunately, this beetle is on the wrong calendar and is restricted to the summer months.
As you can guess from the common name, the beetle feeds on fungus. In this case, I found it chewing on some bracket fungus as night was falling. It's a large beetle (two centimeters long) and its elytra are quite smooth. After I captured it and took it back to the lab, I was watching it move around under the microscope. As I watched it move its leg (it had flipped itself on its back), I was awed by how smooth its movements were.
Truthfully, this beetle showed me how beautiful insects could be, just by something as simple as their movement. It was a "Eureka!" moment for me, and has ensured that this beetle will stay at the top of my list of favorite insects.
Too often we recoil at insects and other small arthropods because they look ugly or creep us out. Casting them down in judgement is ignorant and quite offensive to how elegantly they go about their lives, however. Not until you take the time to immerse yourself in their world (that is, what life is like for organisms that are measured in inches at most) can you truly appreciate the beauty and real magic that nature exhibits.
If you're interested in seeing more of my photographs from the Beiser Field Station, you can find my collection on my userpage at Project Noah.
In Ohio, there's a delightfully gregarious caterpillar known as Manduca sexta, or the tobacco hornworm. It's placed within the Sphingidae family, which is composed of the hawk moths. Take a look at the Wikipedia page for the hawk moths: they're all spectacular. Some of the adult moths resemble birds or bees, they're just amazing. To get back on topic, the tobacco hornworm feeds on tobacco (obviously), as well as other plants within the family Solanaceae, which includes tomatoes. This makes them pests to gardeners, which is pretty unfair. Tobacco hornworms develop into some beautiful moths and are quite large, so they're truly a sight to see once they reach maturity. Luckily for me, they also feed on Datura wrightii, a plant within the same family as tobacco and tomato, which grows near my house.
I had the fortune of finding a few of the caterpillars on the Datura plant, so I plucked them along with some leaves and placed them in a container in my room. They were still in their early instars (An instar is simply a stage in the life of a caterpillar. As it grows, it will molt and enter a different instar, gradually getting bigger as it enters each successive instar.) and so were relatively small, as you can see from the pictures. Of course, they did not stay small for long. I ended up plucking five or more leaves each day for each caterpillar in order to give them enough food, and I still wasn't sure if that amount was enough. They would eat through all the leaves in short order, and sometimes I found myself getting even more leaves for them throughout the day.
And so, they each progressed through their instars, growing larger and larger. I was surprised at just how big they were getting: these aren't small, inch-long creatures. If you're creeped out by large worms or snakes, then you won't like these guys (but you should anyway). Taking a look at the pictures now, you can start to notice their stripes and small eye-like spots on their sides. The stripes are one way to distinguish them from a similar species, the tomato hornworm, which also feeds on tomatoes. It has eight V-shaped markings, while the tobacco hornworm has the seven diagonal stripes*. The stripes serve another purpose as well: camouflage. The stripes break up the hornworm's pattern while it's feeding on leaves, helping it to blend in with the overall shape and color of the plant. If you encounter a plant with skeletonized leaves, it's a good indication that a caterpillar has been feeding on the plant, but even if the caterpillar is still on the plant while you're looking at it, it's no guarantee that you'll find it. They're remarkably hard to find, even when you know they're there (which is remarkably frustrating).
Now, the orange eye-like spots on the hornworm's side are its spiracles. Spiracles are how insects breathe, simply put. It probably doesn't hurt the insect's chances of survival that its spiracles look like eyes, either.
In the picture below, one of the caterpillars has undergone ecdysis (molting), and has entered its next instar. Tobacco hornworms usually have five instar stages, but can have more depending on growth conditions. Near the caterpillar's posterior end, you can see the remains of its previous molt. The caterpillar proceeded to eat these remains. When a kid is growing and needs nutrients, they're forced to eat vegetables. When you're a caterpillar, you eat what used to be your skin. Except for the head case. That part is too hard, so it just pops off and is left alone.
Pictured: a delicious gourmet meal
You can tell that the caterpillars have grown much larger than they used to be. The most mind-blowing fact about it is that these pictures were all taken over the course of about a week. Caterpillars can grow pretty quickly.
Caterpillar excrement is known as "frass." It fertilizes plants and all that good stuff. Also, you can hear it falling down the leaves of trees and other plants like rain sometimes.
The small reddish brown object is the pupa of another caterpillar, Ceratomia catalpae.
Still eating.
At a certain point during the hornworm's fifth instar, it starts undergoing physiological changes signaling its body that it's time to pupate. Different hormones start being produced, and the hornworm's behavior changes. Effectively, it's puberty, but with less pimples. One of the behavioral changes is quite pronounced, and results in the caterpillar entering a so-called "wandering stage." The caterpillar descends from its plant and starts walking around on the ground, looking for a good place to burrow into the dirt. Or, if the caterpillar is in an insect cage, it will walk around the enclosure and stomp on everything. (Various sources recommended that I remove excess frass to avoid a messy situation. It was a very helpful recommendation, and saved me a lot of cleanup time later on. If you decide to raise a hornworm, you would do well to heed the same advice.) After a little while of wandering and being much more active than it was during its feeding stages, the hornworm will start to dig into the soil. It's a fascinating process: the hornworm uses its body as a shovel. It doesn't so much as dig a burrow as pulverizes its way down into the dirt and decides "Yep, this'll do." I found I had new respect for my hornworm after watching it go underground.
Lateral view, the hornworm at work.
The problem with not having quite enough dirt in the insect cage.
A fascinating visual cue that the hornworm has entered its wandering stage is the presence of its aorta (its heart). On the "back" of the hornworm (its dorsal side, for those of you anatomically inclined), the hornworm's aorta pumps its blood (technically hemolymph, I do believe), which is quite conspicuous.
The hornworm's aorta, hard at work.
After the wandering and digging, the hornworm settles in for some huge changes to its anatomy and physiology.
Also notice how the posterior end of the hornworm looks a bit like a face. Some mimicry, perhaps.
While that hornworm is busy pupating, let us catch up with the other hornworm.
.....or not.
And now it is time to learn about one of the most interesting natural phenomena in the animal kingdom: Parasitoidism. You may know about parasites: nematodes, flatworms, and according to some, politicians (we won't get into that argument here). Parasitoids are similar to parasites in that they also live inside of a host and feed from it. However, parasitoids take parasitism one step further. Parasites live and feed off of a host, yes, but they do it in a way that doesn't kill the host. If the host dies, the parasite also dies since it loses its food supply. Parasitoids, on the other hand, have little concern for the well-being of the host. In a parasitoid-host relationship, the parasitoid feeds off the host in such a way that the host dies. The parasitoid has special adaptations that allow it to survive after the death of the host, so to the parasitoid, the final result for the host doesn't matter.
So what does that mean in the context of Manduca sexta?
Manduca sexta has the misfortune of being prey for some species of wasps in the family Braconidae, which contains a variety of parasitoid wasps. These wasps seek out various caterpillars, and when they find them, they lay their eggs inside of the caterpillar. This is bad news for the caterpillar, as its defensive options are limited. The plants it feeds on contain toxic chemicals, and there is evidence that some caterpillars can ingest more leaves containing these chemicals to self-medicate against parasitoid infection**, though such a study has not been researched specifically for Manduca sexta. However, it is not too much of a leap to hypothesize that the hornworms could make use of toxic chemicals in an attempt to kill the parasitoids.
As a side note, such parasitoidism is obviously beneficial for the host plant of the caterpillar, as it can suffer severe skeletonization of its leaves due to the caterpillar's voracious appetite. The plant is not entirely defenseless, however, and is able to release chemicals to attract such parasitoids to rid itself of the caterpillars. To learn more, check out this wonderful article from Scientific American.
So, the hornworm has had the misfortune of being parasitized. What can it look forward to? Aside from the hope that the eggs won't hatch, not much. Its future is pretty bleak. First, the eggs will hatch. The wasp larvae will start eating the insides of the caterpillar. Since they are parasitoids, not parasites, they won't have much respect for the normal, healthy functioning of the various organs and systems of the caterpillar. The little respect for the caterpillar's health that the wasp larvae will have will simply be not eating the vital organs first, allowing the caterpillar to live so that the larvae will have a safe place to develop. Once they have grown sufficiently, the larvae move on to phase two.
The larvae eat their way through the caterpillar's skin. If you go back to the picture of the larvae coming out of the hornworm, you will notice a few dark circles on the caterpillar. Those are wasp larvae eating their way out, almost breaking through the skin. Once the larvae have made it out of the caterpillar, they will immediately start spinning cocoons. They will stay in the cocoons for about a week or two, and then emerge as adults. During all this time, the caterpillar is still alive. Depending on nature's mercy, the caterpillar may die soon after the wasp larvae have burst from its body, or it may stay alive until the adult wasps emerge from their cocoons, and even for a few days after. I imagine the caterpillar curses its existence if it is in that predicament.
Adult braconid wasps emerging from their cocoons.
The cocoons look like small white egg sacks. There can be as many as 50 or more on one caterpillar, depending on its size and unluckiness.
These adult wasps will each seek out other caterpillar targets.
The resulting caterpillar.
For an even more gruesome lesson on parasitoidism, National Geographic has you covered.
Now, time to move on to a healthy hornworm.
Pupal stage.
The caterpillar has undergone quite a change while underground, resulting in its pupal stage (also known as Metapod, to Pokémon fans). The most outstanding feature is the curved tube at its anterior end, which its tongue grows in. The pupa is not entirely defenseless. When touched, it will jerk its posterior end violently, which is quite startling if you do not expect it (I speak here from personal experience). The pupal stage also takes place while buried a few inches underground, which isolates it from many predators.
As the moth gets closer to eclosion (emergence from the pupal stage), the pupa will get darker and more translucent.
It will turn almost purple in some areas.
Finally, the moth will emerge from the pupa. I assume the orange-brown liquid to be hemolymph, though I haven't found a source identifying it for sure.
The pupal stage lasted a little over two weeks, and the final result was...
It's quite a beautiful moth, very "furry." It's also quite large, to the degree of a small bird. Knowing the size of its caterpillar and pupa, it's no surprise.
Check out those eyes! Also notice the tongue curled up into a ball. The adult feeds on nectar.
A full view of the body and wings. Notice the series of orange spots on its abdomen, absolutely stunning. There are six on each side, twelve in all. I assume these are what the sexta (Latin for six) in the species name refers to.
View of the closed wings. The newly emerged moth cannot fly, but must first pump hemolymph into its wings.
Ventral view, with ruler for scale.
It has quite the wingspan.
Truly, it's a beautiful moth. It's a shame they're seen as pests.
This particular specimen is now located in the collections at Marietta College.
For more information about Manduca sexta, check out the following websites:
