Posts Tagged ‘insect’

Insect Minute – Cicadas

Friday, July 27th, 2012

If there is an insect that represents the feeling of summer, I would argue it is the Cicada. At an afternoon baseball game or cook out, a chorus of male cicadas are there providing a soundtrack, doing their most animated singing at the warmest point of the day. This association between summer and cicadas is not unique to North Carolina or North America for that matter. Cicadas are found on every continent, with the exception of Antarctica.  In fact, there are 2,600 described species in the world ranging from very large (110 mm) to relatively small (14 mm), most of which are members of the family Cicadidae. The other family of cicadas, Tettigarctidae, is a very small and relictual group that is represented by two species present only in Australia. These Australian cicadas are known as the hairy cicadas and communicate by transmitting vibrations through vegetation instead of singing like the Cicadas we are familiar with.

The members of the family Cicadidae sing using organs called tymbals which are located on the abdomen of the males. The tymbal is like a drum. A complex membrane with taenidia-like striations running parallel along the surface and as the membrane vibrates and the enlarged chambers within the trachael system in the insects body act as a resonating chamber.

Image from Cicada Mania

Image from what-when-how

The males use the tymbals to attract females and have distinctive calls to ensure that they attract the females in their species. Males and females have tympana on the underside of their abdomen which the females use to hear and orient toward potential mates, while the males use the tympana to identify competeing males.

Image from Cicada Mania

The life cycle of cicadas is pretty neat, a female cicada will lay eggs into the twigs of a woody host plant using a lance-like ovipositor. When the nymph hatches it drops to the ground and, using it’s fossorial legs, burrows into the soil where it spends the majority of its life feeding on juices it sucks from tree roots. The cicadas we are that we hear every summer are known as the dog-day or annual cicada. The latter name is actually a misnomer. Many believe that the dog-day cicada has a one year life cycle when in fact they live under ground for up to 8 years before they emerge. Because they emergence patterns are asynchronous they do not make as big of an impression. When it is time for cicadas to come above ground the nymph will dig to the surface, climb part way up the tree and molt into its adult form.

The periodical cicada get the most attention because of the grand synchronized emergence that occur every 13 to 17 years. These cicadas are in the genus Magicicada, which looks a lot like magic cicada. That is not too far off when you consider that no one knows exactly how they time their appearance. What is it that signals all the members of a brood to emerge at the same time? Some researches have hypothesized that it is a temperature shift, others believe it could be that the cicadas are tracking the seasonal changes in their host plant until they reach 13 or 17 cycles. It could be a combination of both or something else entirely but because they are so long lived it is hard to pinpoint the reason.  Regardless of how they do it, it makes an impact on anyone who is lucky enough to experience it.

photo by billy liar

If you would like to learn more about cicadas there are plenty of websites dedicated to them. They are such enigmatic little creatures it is no surprise!

  1. DrMetcalf database http://www.lib.ncsu.edu/specialcollections/digital/metcalf/cicadas.html
  2. Cicada Mania http://www.cicadamania.com/cicadas/
  3. Track brood emergence of Magicicadas at http://www.magicicada.org/magicicada_i.php

Transcript of Insect Minute 4 – Cicadas

Hi this is Heather with your Insect Minute brought to you by WKNC and the NC State Insect Museum.
Do you love the sound of cicadas singing on a warm summer night? Typically the serenaders you hear are Dog Day Cicadas, which have broods that emerge every year. But, if you were in Wake County in the summer of 2011 you may have heard a different sound. The sound of hundreds of thousands of periodical cicadas singing in unison! These infrequent visitors are in the genus MAGICICADA. Magicicadas have an amazing life history. They live underground as nymphs for 13-17 years feeding on the juices they suck from tree roots. Then, in a synchronized emergence they take to the trees where they molt into their adult forms, feed and mate. Magicicadas have black bodies, orange wing veins and striking red eyes. The dog day cicada has green wing veins and lack red eyes, making the red eyes a key distinguishing character.
Guess what is coming in 2013? You got it; North Carolina will see another grand emergence of magicicadas. So keep your eyes to the trees and your earplugs at the ready!
If you’d like to learn more about the cicadas visit the museum’s website at insectmuseum.org where you find out more about the museum and read our blog where we talk about interesting stuff going on in the world of entomology.

Insect Minute – What is the biggest insect?

Wednesday, July 18th, 2012

When you are in a specialized career, like entomology for example, you are bound to get many questions. Some of the common questions we get are “What is the most dangerous insect?” “Which has the worst sting?” or “Who would win in a fight between place two large insects that would never cross paths here?” We’ll save these questions for future Insect Minutes. The question that we seek to answer this week is, “What is the biggest insect?”

Aggggghhhh!! That is one big insect!!

To answer this question we need clarification, how do you quantify “biggest”? Insects are very diverse and they come in many shapes which means that the longest is not the heaviest.  So to answer the question of what is the “biggest” completely there are two answers.

The longest insect is the Chan’s Mega Stick from Borneo. Phobaeticus chani is a member of the stick-insect order Phasmatodea. Our native species, Diapheromera femorata, is 3 to 4 inches long. Phobaeticus chani is 14 inches long, if you include the legs the length extends to 22 inches!! Despite its large size very few people have seen one, in fact if you searched all the insect collections in the world you would only find that 3 have been collected. All stick insects are masters of camouflage living up to the order’s prefix which comes from the Greek, phasm, meaning phantom. It may be that the Chan’s megastick is even more elusive because they typically reside in canopy of the rainforest.

Phobaeticus chani, or 'Chan's megastick,' mounted and displayed.

Image from FoxNews.com

The aptly named Goliath beetle is arguably the heaviest insect, based on the bulk of the five beetles included in this genus. The Goliath beetle, Goliathus regius, found in western equatorial Africa is the largest of the group weighing in at 3.5oz! This beetle is about the size of a small apple or bar of soap. Not big by vertebrate standards, but huuuge for an insect.

image by opacity (Anne Petersen)

People find the look and docile behavior of these beetles very attractive and keep them as pets. The grubs, or larvae, of the Goliath beetle require a lot of protein while they develop but once the beetle reaches adulthood it relies on high-sugar foods like sap and fruit making them quite easy to care for. The Goliath beetle is also often used in insect fights; a spectator sport that capitalizes on the male beetle’s natural tendency to fight other males when a reproductive female is present.

So, as you can see, these insects couldn’t be more different from one another and yet they are both contenders for the title: The WOOOORLDSSS Biggest Insect!

Transcript of Insect Minute 3 – The Biggest Insect

Hi this is Heather with your Insect Minute brought to you by WKNC and the NC State Insect Museum.
“What is the biggest insect?”  Well that depends, is the longest or the heaviest
The longest insect is the Chan’s mega stick found in Borneo.  The walking stick can be over 1 foot in length! Can you imagine finding an insect the same size as your foot-long sub? Chances are slim any of us will see one, even if we do make it to Borneo because they are well camouflaged, looking just like the limbs of the trees they reside in.
The heaviest insect is only 4 to 5 inches long but what he lacks in length he sure makes up for in mass.  The aptly named Goliath beetle weighs 3.5 oz which makes this beetle about the same size and weight as a bar of soap. Imagine trying to lather up with this guy, the last thing you’ll be is squeaky clean.
If you would like to see pictures of these insects and find out more about them please 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.

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!