Wednesday, October 26, 2011

Creepy-Crawly October: Spiders, Part 1

Hello readers!

It’s time for the first creepy-crawly installment, and what better arthropod to start with than spiders? Arachnophobia (the fear of spiders) is one of the most common phobias. It has been estimated that 55% of females and 18% of males in Western countries suffer from this particular fear (http://webs.wichita.edu/depttools/depttoolsmemberfiles/psychology/publications/Wagener%20&%20Zettle%20Paper.pdf). Despite this widespread fear, spiders are critical to life on Earth. Without spiders, the world would quickly become overrun with insects. Even I, as much as I love insects, can see that this would be a huge problem!

Spiders belong to the Order Araneae. They are a very diverse group, but have several unifying characteristics. They have eight legs, two body regions, no wings, and no antennae. Their relatives include mites, ticks, Daddy long legs (harvestmen), and scorpions. All spiders also have spinnerets and fangs, and all spiders are venomous. Most, however, pose little or no danger to humans.

All spiders (with the exception of a recently discovered species, see here: http://news.bbc.co.uk/2/hi/8302535.stm) are predators. Spiders are well-known for their web-spinning finesse. Spider silk is a remarkable substance, being both strong and very flexible, and is the envy of scientists and engineers. While many spiders spin webs, others rely on stealth and speed to catch their prey, such as many tarantulas. The Bolas spider uses its silk in a very unique manner to catch prey. Check out this video to see its amazing hunting behavior: http://www.youtube.com/watch?v=2UfMJJAzvbI

Spiders have many fascinating courtship rituals. For males, finding a mate can be a dangerous business. A female may decide he would make a better meal than a mate. In general, female spiders are much bigger than males, so a male’s best bet is to make a hasty retreat if things take a turn for the worse. To try to avoid becoming snack food, male spiders employ different methods for alerting a female to his intentions. Some males will tap a certain pattern on a female’s web to let her know he’s not there to be dinner. Jumping spiders have particularly unique courtships. The male spider is usually much more colorful than his female counterpart, similar to many birds. He will perform a complex series of “dance” moves, accompanied by abdomen vibrations. Usually the female can’t help but be impressed! See here for a demonstration of a jumping spider courtship dance: http://www.youtube.com/watch?v=sUypt5lMYUo

After mating, male spiders die shortly after, either by being eaten or naturally. Some males will actually allow themselves to be eaten by the female to help ensure she will produce healthy babies. In any case, the female is on her own when it comes to their offspring. Female spiders are actually very good mothers. Some will capture prey, bury it, and then lay an egg sac on it so her babies (known as “spiderlings”) will have a meal waiting for them when they hatch. Certain tarantula mothers will time their death to coincide with the emergence of their offspring, and the spiderlings will then eat her. Other spiders, such as wolf spiders, will carry their egg sac until the babies hatch. The spiderlings will ride piggy-back on their mom for several weeks. Their mother will protect them and feed them until they are big enough to fend for themselves. Go here to see a video of a mother wolf spider with spiderlings on her back (I think it’s really cute!): http://www.youtube.com/watch?v=axDpsLPhYSg&feature=related

There’s much more to say about these amazing creepy-crawlies, so check back soon for part 2!

Wednesday, October 5, 2011

October Update

Hello readers! Life has been keeping me pretty busy here recently, but new posts will be coming soon. Since it's October now, and Halloween is coming up, I've decided to post about arthropods people consider creepy and gross. Things like spiders, cockroaches, bed bugs, scorpions, and tarantulas. My Mom refers to these critters as "the stuff of nightmares." It should be fun!

Wednesday, September 14, 2011

Insect of the Week! Ambush bugs

These little guys are one of my favorite insect groups. My sister caught two of them earlier this month, and I was very excited! They are true bugs (from the order Hemiptera, which means “half-wing”), meaning they have piercing, sucking mouthparts which they keep tucked underneath their bodies when not in use. As Hemipterans, they also have wings which are half-covered by leathery, opaque wing covers. The uncovered parts of their wings, which they use for flight, are visible towards the end of their abdomen. They also have another unique feature which they share with their close relatives, the assassin bugs. Their abdomen (the region right behind their legs) extends out past their wings on both sides.

Ambush bugs are predatory insects. They are very well camouflaged and often blend right into whatever flower or plant they are sitting on. These bugs are very common on goldenrod, and as such most species are greenish-yellow, brown, and/or black. Here is a page with pictures of some common USA species: http://bugguide.net/node/view/4833/bgpage

Ambush bugs have several adaptations which make them excellent predators including big eyes and enlarged, powerful front legs. They use these to catch and hold their prey. In spite of their small size (about a quarter of an inch), ambush bugs are capable of subduing insects much larger than themselves such as bees, flies, and wasps. The bugs wait without moving for an insect to come too close, and then they quickly grab it. Once the bugs have captured their prey, they inject venom into their victims which both paralyzes them and liquefies their insides. The bug then enjoys its meal by sucking up this “insect soup.”  (Yum!)

Despite their venom and predatory habits, ambush bugs pose no threat to humans. They are too small for their bite to break the skin and can be handled safely. If you find one, try observing it for a while. You may see it catch an unsuspecting insect meal!

Also, feel free to check out this youtube video to see some of the habits of these amazing creatures: http://www.youtube.com/watch?v=ezDOrId-Tq4

Wednesday, September 7, 2011

New feature: Insect of the Week! The Polyphemus Moth

Well, I have already failed in my goal to update my blog once a week. That didn’t take long, but I’m getting back on track and starting a new feature, Insect of the Week!

Insect of the Week!  The Polyphemus Moth

Members of the Order Lepidoptera, which contains the Butterflies and Moths, are considered by entomologists and amateurs alike to be some of the world’s most beautiful insects. The Polyphemus moth is no exception. My Dad caught one of these beauties for me outside his office last Monday.

Check out a photo here: http://bugguide.net/node/view/136372

Polyphemus moths are members of the Family Saturniidae (Giant Silkworm and Royal Moths). This family contains some of the largest moths in the world and some of the most colorfully decorated. They prefer the leaves of trees and shrubs, and each species has their own particular favorites. Caterpillars can grow up to 4 inches long. When they are done munching, they spin a cocoon of silk. After several months, the adult moth emerges. The large eyespots on the wings are thought to be used as a defense against hungry predators by surprising the would-be snacker and giving the moth a chance to escape.

Although the adult moths are beautiful, they do not live long. Most species survive for only a few weeks. They have vestigial (useless) mouthparts and so cannot eat. The sole goal of their adult lives is to reproduce.

It’s very easy to tell the difference in gender of these moths, just look at their antennae! Male moths find females by following their pheromones, which are good-smelling chemicals (to the moths, anyway!). The males have very feathery antennae which allow them to smell the pheromones. Some male moths can detect a female moth from over a mile away!

Other well-known members of this family include the Luna moth (http://bugguide.net/node/view/523517/bgimage) and the Io moth (http://bugguide.net/node/view/172049/bgpage).

Needless to say, I’m thrilled to have a Polyphemus moth in my collection. Come back later this week to learn about one of my favorite insects, the ambush bug!

Thursday, August 25, 2011

The Lowdown on Legs


One of the best things about choosing invertebrates as my blog topic is that I’ll never run out of subject matter! But that also makes it challenging to pick what to write about now. So, today’s topic is legs.

Legs are one of the main characteristics scientists use to separate invertebrates into various groups. For example, all insects, without exception, have 6 legs. Spiders always have 8. Centipedes (the name means “100 feet”) have one pair of legs per body segment and millipedes (name means “1000 feet”) have two pairs of legs per segment. The number of legs found on crustaceans such as crabs and lobsters tends to vary, but usually they have 10 or 12.

All the invertebrates mentioned above are placed in the Phylum Arthropoda, which means “jointed appendages.” Despite having no internal skeleton, arthropods have movable, jointed legs somewhat similar to our own. Below is a link to a diagram of some insect legs and how they compare to human legs.

http://www.daviddarling.info/images/insect_legs.jpg

Arthropod legs are adapted for many different functions, in the diagram. Many insects’ hearing organs, known as tympanum, are found on the first pair of legs. These organs are sensitive to vibrations and are especially useful to insects that “sing” such as cicadas, crickets, and katydids.

I may post on this topic again as I learn more about insect anatomy in my general entomology class. It’s an area I’m looking forward to understanding better!

Wednesday, August 17, 2011

The Incredible Invertebrates


On planet Earth, 99% of all animals are invertebrates. These unique animals find themselves with the challenge of surviving without the bony support system we often take for granted. Now, I mean no disrespect to the faithful backbone. I myself am very grateful for my bony vertebrae.  But we as humans are part of the vertebrate minority. Bodies without backbones far outnumber us, and so in the Animal Kingdom, it seems backbones are somewhat overrated.

So what are some examples of invertebrates? The term covers a wide variety of organisms. Because invertebrates are animals, they meet several key classification requirements. All animals are multicellular, have a plasma membrane around their cells, reproduce sexually (many reproduce asexually as well), and are heterotrophic (they must consume other organisms for sustenance). Invertebrate animals include sponges, jellyfish, flatworms, roundworms, earthworms, centipedes, millipedes, crustaceans (crabs, lobsters, etc), mollusks (octopi, snails, clams, etc), spiders, scorpions, and insects. There are also dozens of less well-known and rather bizarre invertebrate groups.

Now while I find all invertebrates fascinating, I am particularly intrigued by insects. They are the most numerous animals on the planet. They exhibit an astounding variety of body plans, colors, and sizes. Insects have exploited every major ecosystem and are found on every continent (including Antarctica!). They can cause devastation and disease, but are also vital to our survival. Pollinators such as bees allow us to enjoy many varieties of fruits and vegetables. Many insects are predators of the pests that can wreak havoc on our agricultural system. Insects exhibit many fascinating behaviors seen nowhere else in the Animal Kingdom, yet they are often overlooked because of their size and alien (sometimes even scary!) appearance.

The purpose of my blog is to explore the amazing world of insects on a weekly basis. I also plan to highlight some other interesting invertebrates as well. My hope is to educate, inspire, and maybe even change a few minds regarding insects. But even if I never do persuade you to touch or even look at an insect, I hope you will gain a greater appreciation and respect for these remarkable six-legged creatures. And perhaps you may find yourself contemplating the overratedness of backbones.