In My New Skin

Yao Ming
Creative Commons License photo credit: Keith Allison
Yao Ming –
The guy just didnt stop growing.

I bet you’ve never thought of growth in as much detail as I have. As an Entomologist, I think about it a lot! It’s very simple for vertebrates. You eat, drink and sleep - and your body grows. Do you tell your body to grow? Do you try to grow? No, it just happens, slowly at times and quickly at other times. Sometimes we grow up and unfortunately, sometimes we grow out! The point is that it is an involuntary action that our body undergoes, just like breathing, blinking, salivating and blood pumping! I am so grateful to be a human and have this happen effortlessly and without many bumps along the way.  Arthropods, on the other hand, got the short end of the stick! Arthropods have to go through a serious ordeal to get from one size to another, known as molting or more scientifically, ecdysis.

Insects and other arthropods are not like us, obviously! Whereas we have an endoskeleton, or skeleton that supports our body from the inside, they have an exoskeleton, or a hard shell covering the outside of their bodies. This exoskeleton functions much in the same way as ours does. It supports the arthropod, as well as acting as a point for muscle attachment. Additionally, it protects them from certain predators and parasites and helps to keep terrestrial arthropods from desiccating or drying out. It also contains certain sensory structures that are very important to insects and their many relatives.

Exoskeletons are formed by a long chain polymer called chitin. This compound is very tough and resilient and is also found in other animal structures such as the beaks of octopi and squid. When I’m teaching kids about exoskeletons, I like to compare it to a suit of shining armor that a knight would wear. Now, if it was a young knight, he would have to grow, so he could not always wear the same suit of armor. He would have to trade it in for a new, larger one. This is the case with arthropods and their exoskeleton. In order to grow and get larger, they must shed their exoskeleton and grow a new one.

This is where things get a bit hairy! In order to shed their exoskeleton, arthropods have to go through a scientific process called ecdysis. I’ll spare you the boring scientific details, but basically, they excrete a liquid that separates their old skin from their bodies. This process is called apolysis. They then form a new skin. They excrete another chemical which digests the innermost layers of the old skin and they crawl out of what’s left. What’s left behind turns into a dry crunchy empty shell. Shortly before this process, arthropods stop eating, start swelling up a bit, and eventually stop moving or being able to function at all. If anything at all goes wrong during this process, they are finished!

katydid 012

Creative Commons License photo credit: emills1
A katydid nymph molting,
getting a little help from a friend!

Many insects have to hang upside down and let gravity help pull them out of their old exoskeletons. If they fall from their perch before they are done, they will not be able to get everything out and will either die or be severely deformed. To make matters worse, they are super defenseless during and after this process, making them prime targets for predators! If an arthropod is able to successfully complete their molt, they are stuck with this brand new, super soft exoskeleton. They can neither walk nor fly. They are completely vulnerable for at least a couple of hours. Have you ever eaten soft shell crab? Well, it’s not some cool different species of crab you’re eating, it’s just a regular crab that has been harvested right after molting. They cook it while it is still soft, so you’re eating the whole crab, shell and all. I can’t ever bring myself to eat them, it kind of grosses me out! The most commonly used crab for this, in the United States, is blue crab.

Feb2010 069

Creative Commons License photo credit: emills1
A deformed katydid due to a failed molt

If the arthropod is able to successfully remove all body parts and limbs from the old skeleton and find a safe place to rest until their new skeleton hardens, they can go on living their little bug lives, until the next time they have to molt! This process gets even more complicated in insects that have what we call complete metamorphosis, such as butterflies, beetles, flies and bees. Insects like grasshoppers, cockroaches and praying mantises go through incomplete metamorphosis, so every time they molt, they have relatively little changes in their bodies. They mainly get bigger and some grow wings. As we all know, a butterfly starts out as a caterpillar, it gets bigger as it molts, but when it’s time for it to pupate or form a chrysalis, the process of molting involves the insect changing its body completely. This makes it even MORE of a challenge for them.  It’s very interesting to note that similar chemicals that digest the insect’s old exoskeleton, digest most of the actual cells of the larva, leaving only some cells alive. These remaining cells reform the organism into a completely different looking organism, like the adult butterfly!

Feb2010 084

Creative Commons License photo credit: emills1
The Exuvia of a Giant Prickly Stick,
a walking stick from Australia.

The cast away skin of an arthropod is called the exuvia or exuvium. When it’s first removed from the animal, it’s soft, like the new skin, but as it dries out, it becomes very crunchy!

I bet almost everyone has seen one of these. You know those empty insect shells you can sometimes find stuck on trees? I grew up calling them locust shells and I used to love scaring my siblings and friends with them. Then I’d get a lot of pleasure out of crumbling them up! Well, they are not locust shells; locusts are a type of grasshopper. These exuviae belong to cicadas.

Tibicen Cicada
Creative Commons License photo credit: jasonb42882
A cicada molting.

Cicadas are those funny looking insects you hardly ever see but always hear in the summer. You can hear the rattling noise they make during the hottest hours of the day. The immature cicadas can spend anywhere from 2 to 17 years feeding on tree roots underground, depending on the species. They emerge at night, start climbing a tree, and complete their final molt to adulthood on the way up. The next day we find the shells, but the actual cicadas are high up in the tree tops by then!

Every arthropod on the planet has to go through metamorphosis that involves molting. Insects, spiders, centipedes, millipedes and crustaceans. Interestingly, millipedes are born with only a few segments and legs. Each time they molt, they add another segment and 4 more legs.  I could go on and on about the amazing molting process. The point is, next time you are getting down about anything in your life, think about how easy we have it compared to the bugs of the world. Be thankful that we have easy access to resources we need to survive, we have no real predators and we don’t have to molt! The whole process terrifies me really, so I’m very thankful!

Until next time, happy bug watching!

Ghosts in the Trees

Last night, I was reminded of how unusual some of the insects we raise here in the Cockrell Butterfly Center are to most people. I had set up a table in the grand hallway of the museum to promote our outreach program, cleverly titled “Bugs on Wheels.” As soon as I left the Butterfly Center’s doors, I had drawn a crowd that didn’t seem to subside for the entire evening!

I think what grabs most people’s attention are our exotic walking sticks, which we have been displaying for several years. As soon as people see our giant prickly stick, they commence with “what on earth is that?” type of comments, and I love to educate them!

Walking sticks belong to the insect order Phasmatodea or Phasmida. This name comes from the Latin word phasma, which means ghost. It refers to their amazing camouflage skills, which in the right setting, can make them vanish right before your eyes! These insects are all herbivorous and harmless, having no venom or large mandibles for biting. This makes them an easy target for insectivores! So they have come up with some pretty fantastic ways to protect themselves from predators. These insects have simple metamorphosis, so the immature nymphs, look like tiny versions of the adult. Here at the butterfly center, we raise 5 different species of exotic walking sticks. I’d like to share a little about each one with y’all!

Blog 027

Creative Commons License photo credit: emills1 
an immature female

The Giant Prickly Stick, or Extatasoma tiaratum, is one that really draws the crowds! The females are very large, 6 to 8 inches in length, and very fat! They range in color from light peach to dark red-orange. They are often – almost all the time, actually - mistaken for a scorpion. This is no accident, this species is native to Australia, the venom-capital of the world! They spend their entire lifetime hanging in eucalyptus trees feeding on the yummy foliage and easily folding themselves to resemble a dried up leaf.

If they are spotted by a potential predator, they will curl their abdomen to look remarkably like a scorpion. This warns predators that if they don’t want a nasty sting, they should stay far away. What a clever defense! Since they are, of course, completely harmless. They have a very soft exoskeleton which keeps them confined to the safety of the tree tops. If they need to do anything like lay an egg, they drop it to the leaf-covered ground. The females have small vestigial wings, but are incapable of flight. They can lay up to 1,000 eggs in their lifetime and can live a little over a year. The males are quite a bit smaller, very thin, and excellent fliers. They are equipped with much longer antennae than the female, which they use to sniff out a mate.

BOW 024
Creative Commons License photo credit: emills1
Spiny Devil

The Spiny Devil (Eurycantha calcarata), is a close neighbor of the prickly stick; they are native to New Guinea. These adorable stick insects have very different habits. They are equipped with a very hard exoskeleton that is covered in hard spines, especially the legs! Since they are a harder egg to crack, they are not as attractive to eager insect-eaters, plus, they put up quite a fight! They can use their legs as a weapon by squeezing with all of their strength. I can speak from experience and say, it hurts!

When threatened, they can put on quite a show, raising their abdomen and back legs. We like to call it “the handstand of pain!” Since the female has the freedom of reaching the ground, she uses the pointy tip of her abdomen (her ovipositor) to lay her eggs deep in the soil. The male and female look quite similar, both are wingless and they are nearly equal in size. Both sexes can live for about a year and a half as adults – not bad! The male does have one distinguishing characteristic, a single very large spine on his hind femur.

Blog 061
Creative Commons License photo credit:
emills1 Ouch!

They are very territorial and use this spine for fighting. They can seriously injure or even kill another male during combat. Still want to mess with these guys? Well, the males can also emit a very foul chemical that smells just like a skunk. However, they are usually pretty laid back.

The Phyllium celebicum or moving leaf insect is a breath of fresh air. These leaf mimics are petite, dainty, have no spines or smells, and are 100 percent cute! They inhabit the rain forests of Malaysia.

Blog 033
Creative Commons License photo credit: emills1

Since they have no other defense mechanisms, their camouflage has to be absolutely perfect, and well, see for yourself! They also spend their entire lives in the canopy, dropping their eggs to the ground haphazardly. The female, pictured right, has larger wings than the Giant Prickly Stick, but their only function is camouflage. The male is half the size of the female and he’s an amazing flyer! These live a little under a year and we love to have them around.

I actually noticed something very interesting from observing them. The outer 1/2 inch of the female’s body is only a layer of skin, and all of the organs are arranged down the very middle of the abdomen. This is important because I started seeing a couple of them missing chunks of their abdomen, but they didn’t appear to be injured. I’m sure they get nibbled on by several herbivores in the wild - it’s a pretty cool adaptation.

Blog 043
Creative Commons License photo credit: emills1

Sharing the same rain forest is the Giant Jungle Nymph (Heteropteryx dilatata). They are spectacular, very large and beautiful. The females are bright green and usually 7 inches in length with a wide abdomen. They have small wings which they rub against their bodies to produce a hissing noise. Their thorax, abdomen, and legs have rows of sharp spines. When disturbed they thrash around violently and they also do “the handstand of pain.”

They spend most of their time in the trees and only travel to the ground to lay their eggs. The male is brown and only about 4 inches long. They have bright crimson hind wings and are very showy. They are always very nervous and thrash around a lot! This species is harder than the others to raise. They need high humidity and they take a long time to develop.

Blog 057
Creative Commons License photo credit: emills1
a male

The eggs take around 17 months to hatch and the nymphs take over a year to develop into adults. This species can be very aggressive, but we always end up with a few that can be handled, they are very curious and active. 

The last resident of southeast Asia is the Annam stick insect (Baculum extradentatum). These look very similar to our native walking sticks. They are very slender and really resemble a twig. These are interesting little creatures. When disturbed, they will essentially go limp and flop to the ground. It’s really the only option for them since they are so defenseless.

The most interesting thing about this species is that they can be completely parthenogenic. This means that the females can reproduce without males. We do have males in our populations and it is a full time job making sure we don’t have too many individuals. They are egg-laying machines. Their life span is about a year and males and females look very similar, but the males are much smaller.

These walking sticks are some of the most amazing insects I’ve worked with. I’m so impressed with their diversity and beauty. Next time you see them in the Entomology Hall or in the Grand Hall, come by and see them, you’ll certainly be amazed!

Blog 041
Creative Commons License photo credit: emills1
male
Baculum





Tunicates & Taxonomy

Next month, I will be teaching a class about animal groups, families, & taxonomy. Taxonomy shows us how animals (or other objects) are related to one another in a hierarchical structure. There are 7 major groups which we regularly classify animals into, but there are also a wide variety of sub- or super- categories. The major groups of biological classifications are listed below with two examples written out:


American Crow
American Crow
  American Crow North American Giant Octopus
Kingdom Animalia Animalia
Phylum Chordata Mollusca
Class Aves Cephalodpoda
Order Passeriformes Octopoda
Family Corvidae Octopodidae
Genus Corvus Enteroctopus
Species C. brachyrhynchos E. dofleini

Depending on whom you ask, you may find there are 30-38 phyla, the major categories of animals based on their general body plan and developmental or internal organizations. These phyla can vary from containing only one species (Placazoa) to well over a million (Arthropoda).

Coming from a Zoology background, I found that I really like taxonomy and seeing the order and relationships between animals helps me to make sense of how a rock hyrax and an elephant could possibly be close cousins. They are connected in a group called Afrotheria, a superorder of Eutheria (placental mammals) whose relationships have been shown through molecular & DNA anylases.

Here are their classifications:


Rock Hyrax
Rock Hyrax
  Asian Elephant Rock Hyrax
Kingdom Animalia Animalia
Phylum Chordata Chordata
Class Mammalia Mammalia
Infraclass Eutheria Eutheria
Superorder Afrotheria Afrotheria
Order Proboscidea Hyracoidea
Family Elephantidae Procaviidae
Genus Elephas Procavia
Species E. maximus P. capensis

An article came my way about very unusual sea animals found in Antarctica. When I saw the beautiful picture of the tunicates (also known as sea squirts), I wanted to remind myself what these interesting creatures were and who they were related to in the big tree of life.  Although they may look more like “glass tulips” than an animal, these creatures do eat & grow like other animals.  In fact, tunicates are in the same phylum as ourselves, Chordata.  Tunicates, ourselves, hagfish, fish, and other chordates all go through similiar developmental stages that include a notochord (provides support), pharyngeal gill slits (used in feeding), and a tail (helps with locomotion). 

When born, tunicate larvae are similar to small tadpoles, swimming about until they find a suitable rock to settle down on as an adult, cementing themselves to their new home.  Next, they go through many physical changes before fully becoming an adult.  Some tunicates will continue to stay afloat in the ocean their entire lifespan, going through similar metamorphosis as their sedentary cousins.  Tunicates are filter feeders, with in- and out-current siphons.  Food and water is filtered in through their these siphons, then expelled out along with any waste products. 

Here are a few unusual and interesting facts about tunicates:

  • Tunicates are the only animals capable of producing cellulose – produces cell walls in green plants.
  • Tunicate blood contains a high concentration of the metal, vanadium – a metal used to make Lacrosse shafts and simulated Alexandrite jewelry.
  • Tunicate fossils go back as far as the early Cambrian – about 540 million years ago.
  • Tunicates are said to “eat its own brain” during metamorphosis - the tunicate body digests the cerebrial ganglion – a mass of nerves that have a role similar to a brain.
  • Some Tunicates have recently been descovered as invasive species, sometimes hitching a ride on the hulls of ships from one ocean to another.
  • Tunicates are the vertebrates closest living relative.
  • Tunicates are currently being studied in science for certain chemical compounds useful in fighting cancer.


Royal Blue Tunicate
Royal Blue Tunicate
  Royal Blue Tunicate
Kingdom Animalia
Phylum Chordata
Subphylum Urochordata
Class Ascidiacea
Order Enterogona
Suborder Phlebobranchia
Family Diazonidae
Genus Rhopalaea

Big BEETLE Bonanza!

Last week I was wondering around the containment room looking for something to do. It’s not like I had nothing to do, but I was just looking for something different that day. I decided to tackle the 24 containers full of dirt and grubs. About a year ago right after we opened Erin got an exciting phone call. A guy had LIVE beetle grubs in a wood/compost pile in his back yard and he didn’t know what to do with them, so he decided to call us. We jumped on this one and told him to bring them our way. Phone calls like that are normal around here, but they are extra special when it involves a large live insect that we get to keep. He brought the grubs in a large trashbag with lots of dirt and wood. It was like opening up a huge Christmas present with lots of little presents inside. We found 24 grubs. We weren’t sure what type of beetle they were, but we knew they could either be the Ox Beetle or the Eastern Hercules Beetle.

Erin and I were fortunate enought to raise a few Dynastes hercules grubs a few years back, but it was only a few, not 24. We decided to give each grub an individual container. We kept the dirt they came in and mixed in some potting soil, ecoearth, and lots of rotten wood. After that we sat back and waited. About once a month we would make sure they were all still alive and add new dirt and wood if needed. We would also check the moisture in the containers every now and then and added water as needed.

So . . . last week I thought I would add all new dirt and wood to all the grub containers. Erin and I had collected some rotten wood the week before just for that purpose. I was a little nervous to dump out all the dirt from each container because there was a possibility one of the grubs had pupated. Beetles have complete metamorphosis in which they have an egg, larva, pupae, and adult stage. The grubs enclose themselves in a cell of dirt and saliva before they go into the pupae stage and the last thing I wanted to do was bust open that enclosure.

This is what happened . . . I got the first container with great anticipation. I read that it takes about 12 months for the grub to grow, pupae, and become an adult. Maybe, just maybe we would have adults. I slowly and carefully dumped out the dirt and to my surprise there was NOTHING. I was very puzzled but Erin soon informed me that she had found a wandering escapee and put it into another large dirt bucket we had. So, I moved onto the second containter and found a grub. I added all new dirt and fresh rotten wood and went to the next one. I think I found 4 grubs and then my luck changed. I dumped out all the dirt and discovered an ADULT! I’m pretty sure Erin thought I was crazy because I screamed and was so estatic. We had a female ox beetle, Strategus aloeus. We really wanted the eastern hercules beetle, Dynastes tityus, but this was still cool. I found a total of 8 adult females but no males. Fortunately, we have a male that we collected last summer, so maybe we will get babies. On the last container that I opened I busted open a pupal cell and found a wiggly pupae. I decided to just leave it in the containter on top of the dirt. I kept checking on it last week and yesterday I found that a female had emerged from it. It always makes us feel like such good parents when we successfully raise baby bugs. All the beetles are on display in the insect zoo so you should definitely come and check them out.

One more quick story that happened last night after I wrote this blog. My husband, Nick, called me outside because he thought our dog had caught a snake or something and he wasn’t about to investigate it himself. I crept out into the grass and saw something moving. After I got a flashlight I discovered that is was in fact an Ox beetle, just what I had written about that day. Fortunately, it was still alive so I released it into my front yard away from my dogs. It must be the time of year for Ox beetles so keep an eye out in your yard for these amazing creatures.

If you can see this, then you might need a Flash Player upgrade or you need to install Flash Player if it's missing. Get Flash Player from Adobe.