Posts Tagged ‘insects’

Insect Minute – The Arctic Woolly Bear Moth

Friday, July 13th, 2012

As a kid in North Carolina, many of us grew up with the notion that banded woolly bear caterpillars could be used to predict the severity and length of the coming winter. If the band around the center of the caterpillar’s body was wide, we knew we were in for a winter full of snow days and sledding! I am sorry to report that this is, indeed, a wives’ tale. There can be a lot of color variation within one clutch of banded woolly bear caterpillar eggs and the band width typically grows with age. Disappointed? Me too.

Banded woolly bear - Photo by graftendno1

Never the less, there is a woolly bear caterpillar that does have a very interesting relationship with winter. It is called the Arctic woolly bear caterpillar. Although their names are similar and they superficially look alike, these two are very different. The banded woolly bear caterpillar is in the family Arctiidae and is common in all of North America. The arctic woolly bear is member of the family, Lymantriidae, and is found in the Arctic Circle.  This is where is gets really interesting, folks.

The banded woolly bear has two broods in the summer, the first of which pupates and emerges in the same year, the second will pupate over winter and emerge the following spring. The life cycle is very different in the Arctic. Due to the brief growing season, the caterpillar has to feed for several summers to achieve the critical body mass it needs to pupate. As the arctic woolly bear awaits the coming summers it overwinters as a caterpillar, hiding in a hibernacula, allowing the body to freeze, relying on cryoprotectants, such as antifreeze compounds, to minimize permanent tissue damage caused by temperatures nearing -60°C. When the summer returns the caterpillar thaws, reanimates and returns to feeding. This cycle can repeat up to 14 times, meaning 14 years (!) of freezing and thawing and eating, before it pupates and becomes an adult. However a 1998 study by Morewood and Dean showed that it is more common for the cycle to continue for 7 years before pupation. Still, quite impressive!

Arctic Woolly Bear from Discovery documentary, Frozen Planet

Transcript of Insect Minute 2 – Arctic Woolly Bear:

Hi this is Heather with your Insect Minute brought to you by WKNC and the NC State Insect Museum.
The Arctic circle is an unlikely place to find an insect, right? WROOONG! Insects are everywhere and have adapted cool strategies for contending with harsh conditions. The Arctic Woolly Bear Moth is native to this extreme environment. Upon emerging from its egg, the caterpillar begins to eat voraciously. As summer comes to an end it finds a rock to hunker down on and as the arctic freezes over, so does the caterpillar. When the thaw returns the following June, the caterpillar reanimates and returns to its frantic feeding schedule. The cycle is repeated 7 times, which means this moth lives as a caterpillar for 7 years, freezing and defrosting every year. It survives by producing a kind of antifreeze in its blood which protects vital areas from freezing. In the final year the caterpillar develops into an adult, mates, lays eggs and the cycle for the next generation begins.
If you’d like to learn more about the arctic woolly bear visit the museum’s website at insectmuseum.org where you also find out information about the museum and read our blog where we talk about interesting stuff going on in the world of entomology.

Want to read more?

  1. Morewood, W. Dean & Richard A. Ring (1998). “Revision of the life history of the High Arctic moth Gynaephora groenlandica (Wocke) (Lepidoptera: Lymantriidae)“. Can. J. Zool. 76 (7): 1371–1381. DOI:10.1139/cjz-76-7-1371
  2. ARCTIC WOOLLY BEAR WEBSITE (!!!) – http://www.arcticcaterpillars.org/Site/Arctic_Woolly_Bear/Arctic_Woolly_Bear.html
  3. Bennett, V.A., Lee, R. E., Jr., Nauman, J.S. and Kukal, O. (2003) Selection of overwintering microhabitats used by the arctic woollybear caterpillar, Gynaephora groenlandica. CryoLetters 24(3): 191-200.

Insect Minute – The Wonderful World of Bees!

Thursday, June 21st, 2012

Furry, colorful and industrious bees radiate a charisma that people are naturally drawn to. After all, they produce the celebrated product, honey, and pollinate crops and gardens. Like most people, I knew there were three kinds of bees: the honey bee, the bumblebee and the carpenter bee. What I did not realize until I started studying bees, is that there are over 20,000 species of bees world wide and that these represent only a small portion of the bee diversity out there. There are over 3,500 species in the United States!

Bees are in the order Hymenoptera which also includes wasps, ants and sawflies. Bees and wasps are commonly confused with one another or perceived as names that are interchangeable. Bees and wasps share some attributes; like a similar body plan and they are both holometabolous insects. (A much cuter explanation of metamorphosis) There is one very big thing that sets them apart, their diets! Bees are strictly vegan, preferring to forage on pollen and nectar, whereas most wasps mix other arthropods into their diets.

Common Misconceptions:

  1. Bees bite: Well, not usually. Bees have mandibles but they do not typically use them in defense. The main mode of defense is the stinger, a modified egg-laying structure, found only in females. Males are largely defenseless.
  2. Bees and Wasps are the same thing: It’s true that they are related and very similar anatomically, but there are some major differences. As mentioned above, their diet. Most bees are much fuzzier than wasps, having branched hairs that help them collect pollen.
  3. All bees live in hives: Honey bees do, but most bees are solitary which means they live on their own provisioning their brood cells with pollen and nectar. They typically rest on the backs of leaves, in crevices, or in their unfinished brood cell.
  4. Bees attack people: When a honey bee hive is disturbed the bees may give chase, but most bees will not. In this instance the bees are defending their hive and are attempting to scare off a perceived danger to the colony. Typically bees, including foraging honey bees, are quite docile and are unlikely to react to your presence. In my studies working with bees, I have petted a bee on it abdomen while it foraged and it responded by simply flying away.
  5. Bees are only black and yellow: So not true!! Many are black with some hue of yellow, but they come in a rainbow of colors. Check out this beautiful metallic green sweat bee. Gorgeous!

photo by bob in swamp

Transcript of Insect Minute 1 – Bees:
Hi this is Heather with your Insect Minute brought to you by WKNC and the NC State Insect Museum.
When you think of bees you may immediately think honey bee or perhaps the fuzzy bumble bee or a wood loving carpenter bee that is boring holes into your back porch as I speak.
BUT BEES ARE SO MUCH MORE DIVERSE!
You may be surprised to find out that there are over 20,000 different species of bees in the world! and that there are over 3500 here in the United States. Most bees are not social like honey bees. They may live as solitary insects or in small groups with a queen and a handful of female offspring to assist in collecting pollen and nectar for the next generation.
Bees also come in a myriad of colors…
We are all familiar with yellow and black bees, but they also come in green, blue, purple, and even rainbow! It is their diversity that makes them able to occupy many different habitats and act as effective pollinators!
If you’d like to learn more about the diverse world of bees visit the museum’s website at insectmuseum.org where you find out about our museum and read our blog where we talk about interesting stuff going on in the world of entomology.

Podcast to come soon!

Insect Morphology Seminar – Hindgut & Malpighian tubules

Sunday, March 4th, 2012

The Alimentary Canal, please note the hindgut and Malpighian tubules. (From The Insects: Structure and Function, By Reginald Frederick Chapman)

This week Trish gave an enlightening presentation about the hindgut, its function and the importance and variability of the Malpighian tubules. The hindgut is the terminal segment of the insect’s alimentary canal and is comprised of the Malpighian tubules, the pylorus region, the ileum and the rectum. Reabsorbing water and salts from the excrement of the insect before it is excreted is the primary function of the hindgut. The most anterior section of the hindgut, the Malpighian tubules, look like vermicelli noodles that are attached at one end to the hindgut, the pylorus region, and are free-floating in the hemocoel at the other end. They are responsible for absorbing the nitrogenous waste from the hemolymph, which is then transported into the hindgut to be excreted. The number and presence of Malpighian tubules can be extremely variable throughout Arthropoda. Schistocerca has 250 (!!) and at the other end of the spectrum Coccidae have two. Then there is Collembola, which doesn’t have any!

Colin presented a paper about Reticulitermes flavipes, the common wood-eating termite in the southeastern United States. Wood-eating termites have carbon-rich diet but are deficient in nitrogen.  The termites synthesize uric acid but lack the enzyme, uricase, to brake it down into the usable form of nitrogen that they need. By using multiple tracer experiments the researchers were able to follow the path of uric acid through the termite’s system and they found that the uric acid is absorbed by the Malpighian tubules and transported to the sac in the ileum filled with symbiotic but bacteria. The bacteria brake down the uric acid into two parts, nitrogen and ammonia. The ammonia is excreted and the nitrogen is reabsorbed.

Keith presented a paper that explained how Chironomid larvae use their hindgut and Malpighian tubules to protect them from high levels of cadmium in their environment. Cadmium is a heavy metal that is highly toxic to living organisms because it is similar to calcium and will block calcium receptors causing bone softening in vertebrates, but many aquatic insects are insensitive to cadmium. The researchers in this paper found that Chironomids are capable of withstanding 25,000 to 500,000 times the LC50 values recommended by the United States Environmental Protection Agency. How do they do it?! Aquatic insects that are able to withstand such a toxic brew utilize at least one of three strategies. They may form a physical barrier (limits the uptake of the metal), excrete the metal through the fecal matter or urine, and metal detoxification. In detoxification the metal is sequestered by proteins and/or incorporated into inorganic crystalline concretions which makes the metal incapable of exerting its toxic effects. The researchers in this paper found that sequestration through the midgut and Malpighian tubules was very important method for Chironomid larvae. The cadmium would be pulled from the hemolymph by the Malpighian tubules and transported to the hindgut and eliminated. The most fascinating thing about this system is that if there is too much cadmium in the larva it will store it in the Malpighian tubules and not pass it into the hindgut. When the insect pupates, to make room for the adult tubules, the larval tubules are eliminated and the cadmium goes with it. How cool it that?

These two papers are a tie for the best of the week, cadmium sequestration vs. waste recylcing, it is just too difficult to pick one!!

Other papers of note:
1. How do mosquito larvae survive when the salinity concentration in their body is so much higher than that of their environment? Here is a nice photo she drew for us to help explain.

2. Malpighian tubules have stand alone pacemakers?! In Drosophila they do!
3. We know water is reabsorbed in the hindgut, but how does it happen. READ IT HERE!