28 August 2009

Tree Crickets

Thanks to Carl Strang of Nature Inquiries, I will never hear the peaceful silence of a clear midsummer day or night the same way again. In fact, I'm not sure how I have lived so many years without realizing that instead of silence, an unappreciated symphony of harmonious chords plays daily and nightly as male Orthoptera attempt to charm their female counterparts. Back in February, Lindsay and I attended the 2009 Wild Things conference in Chicago, where Carl gave an insightful presentation on singing insects that will forever change how I use my senses when afield. I am thankful that I decided to attend that presentation and grateful to Carl for opening my ears.

Singing insects are made up of Crickets, Katydids, Grasshoppers, and Cicadas. Each of these groups is further split into sections; for example, the Crickets are further divided into Field and Bush Crickets, Ground Crickets, Tree Crickets, Mole Crickets, and Trigs. Each of these sections is made up of numerous species. The Tree Crickets, which are up to about an inch long, are a particularly interesting group made up of two genera (Oecanthus and Neoxabea) in the United States and Canada. In the recording below, I am pretty sure that the long, melodious trill in the background (much like the song of the American Toad) is one or two species of Tree Cricket, while the louder "dee-did" is the characteristic call of the Common True Katydid (Pterophylla camellifolia). I've just started learning these insects, so if anyone disagrees with my assessments, please let me know. I apologize for the poor sound quality.

While some singing insects, such as Grasshoppers, call during the day, Tree Crickets call primarily in the evening and at night. Their purpose, as is the purpose in most cases of song in nature, is to attract a mate. Tree Crickets "sing" by holding their wings upright and rubbing together ridges on their forewings. Once a male has attracted a female and she approaches, the male begins to secrete a sweet liquid from the metanotal glands (also descriptively called "honey pots") on his back. The unsuspecting female climbs onto his back to eat this tasty treat, and as she is doing so, the male sneaks a spermatophore onto to the female. The longer she stays to consume this "love juice," the better chance there is that he will be successful in reproducing.

In the photo above, I have a Tree Cricket in the genus Oecanthus in the palm of my hand. Several of the species in this genus can be told apart from one another by the number and organization of black spots at the base of their antennae. By clicking on the photo to expand it, you can see black spots, but I can't tell for sure how many are present. Possibilities for this species include Snowy Tree Cricket (Oecanthus fultoni), Four-spotted Tree Cricket (Oecanthus quadripunctatus), Davis's Tree Cricket (Oecanthus exclamationis), and Narrow-winged Tree Cricket (Oecanthus niveus).

Above is a member of the other genus of Tree Cricket; this is a Two-spotted Tree Cricket (Neoxabea bipunctata), the largest tree cricket in North America. Two-spotted Tree Crickets are found throughout most of the eastern half of the United States. Be sure to click on the photo above to expand it for more detail.

I am just beginning to learn about singing insects, but I am quickly becoming obsessed with them. Much of the information in this post is from The Songs of Insects, a wonderful and beautiful book by Lang Elliot and Wil Hershberger that can also be found online at http://www.musicofnature.com/songsofinsects/index.html.

Now I just need to learn how to find and recognize more of these incredible creatures!

24 August 2009

An Undeniably Showy Sedge

"Sedges have Edges." That's the saying that all budding botanists learn in their first college botany course to help them remember how to differentiate a sedge from a grass or a rush. This saying is referring to the fact that the culms, or stems, of most (but not all) sedge species are triangular in cross-section. While there are several better ways to distinguish between the monocot families, this is apparently the character that academics thought would be easiest to teach, as the others often require use of a handlens and some patience. For example... Grass (Poaceae) flowers are modified into glumes subtending lemmas and paleas, within which the pistil and stamens are located. Rush (Juncaceae) flowers are comprised of tepals (petals and sepals) surrounding the stamens and pistil, with the structure one expects of a typical flower. Sedge (Cyperaceae) flowers are modified into scales subtending pistils, stamens, or both, sometimes with a corolla modified into bristles. When the ovary of a sedge flower matures to fruit, it is called an achene. In Carex, the largest genus within the Cyperaceae, the flower and later the achene are surrounded by a papery sac, called a perigynium, which is thought to be a highly modified bract.

Bristlystalked Sedge (Carex leptalea)

Unfortunately, the general public doesn't see sedges as anything more than "grass." The perigynia are often brown or green and small, and most often go unnoticed by the untrained eye. The most conspicuous portion of the plant is often the long, narrow, grass-like leaves. Personally, I disagree with the general public, and think that most sedges are quite intriguing and beautiful, once you get to know them.

Northeastern Sedge (Carex cryptolepis)

Yellowfruit Sedge (Carex annectens v. xanthocarpa)

While some will argue that most sedges are not showy, there is one sedge in North America that truly stands out from the rest. Instead of having brown or green perigynia, Golden Sedge (Carex aurea) has round, fleshy, orange perigynia (when mature) that look like tiny pumpkins! It is unknown why the perigynia of this species have evolved to this form, but some speculate that this may assist the plant in being dispersed by birds.

Golden Sedge (Carex aurea)

Golden Sedge can be found growing in wet, alkaline soils throughout most of the continent, with the exception of the southeastern United States and extreme northern Canada.
Who could think that this unique little plant is not attractive?

14 August 2009

Fruit of the Gods? I Don't Think So!

I often hear people, when talking about a non-native plant species, say, "I hate that plant." To this, my response is always, "Don't hate the plant, hate the people who brought it here." Plants obviously don't have the ability to know that they are invading an area to which they are not native, so why hold them responsible? Even today, when invasive species are well known and discouraged in landscaping and erosion control projects, some people still intentionally introduce them. Is it the plant's fault? I don't think so.

This being said, there is one genus that I truly hate. Well, hate is a strong word, and I do still have a degree of respect for this genus, so let's just say that I dislike this genus. The genus to which I am referring is Ambrosia; the Latin name refers to the fruit of the gods (why, I have no idea). In this part of the country, there are two common species of ragweed: A. artemisiifolia v. elatior and A. trifida. Here, I will discuss the latter.

"It isn't attractive," you say, "but Scott, why do you dislike it so?" Here's why... Ambrosia trifida is known more commonly as Giant Ragweed (or Great Ragweed). I learned at a young age, when I thought that ragweed was the yellow-plumed plant covering old-fields and blooming in August and September, that I was severely allergic to the pollen of ragweed. I later learned that this yellow-flowered plant that I saw flowering when hay-fever was setting in, is actually goldenrod (Solidago spp.), which has heavy pollen that is spread by insects rather than by the wind, as the pollen of ragweed is spread. There were many late afternoons in my youth that I was laid out on the couch with a wet washcloth on my eyes to reduce the swelling, struggling to suck in every precious breath. Even as recently as 10 years ago, before I was introduced to the miraculous nasal spray Flonase, I would go to bed on a humid August night wondering if I would be able to breath until I woke up in the morning. Yeah, ragweed and I don't get along.

All of this said, it is still quite an impressive plant. Giant Ragweed, a member of the Sunflower Family (Asteraceae), can reach heights of nearly 20 feet tall, dying back annually and doing it all again by starting as a new seedling the next spring. The rough-textured, deeply 3- to 5-lobed opposite leaves can also produce a short-lived rash if you walk through enough of them, which I certainly have. The flower structure is also unique in Giant Ragweed. Most of the flowers are staminate, meaning that they are only male flowers. The pistillate, or female, flowers, are few and at the base of long spikes of staminate flowers. The flowers lack petals, causing them to be unattractive to insects as pollinators. That's alright... the wind has no problem dispersing the tiny, lightweight pollen grains. Giant Ragweed often forms large near-monoculture colonies in disturbed and alluvial soils, and grows in 47 of the continental United States (how did Nevada get so lucky?). It is said to be native throughout much of its range.

Above, you can see the individual staminate flower heads, consisting of green phyllaries and yellow pollen-covered clusters of stamens, representing disk flowers. Below is a typical leaf of Giant Ragweed.

After walking through a field of Giant Ragweed, my clothes are often yellow as a result of being covered in pollen. I also often see puffs of yellow raining down from the plants when I bump into them. The result can be seen below, as pollen grains cover anything with which they come into contact.

More impressively, below is a photograph of a pollen grain of Giant Ragweed under a scanning electron microscope. This photo is from http://pro.corbis.com/Enlargement/Enlargement.aspx?id=IH056326&ext=1, © Lester V. Bergman/CORBIS. You can see the mace-like appearance of the individual pollen grain. The spikes allow the grain to cling onto anything it touches, and also severely irritate the inside of my nose. I'm sneezing just thinking about it!

Even though Giant Ragweed causes me and countless others so much discomfort, hopefully you can see why it is still difficult for me to truly hate this species.

09 August 2009

A Sunday Walk in the Park

Our friends Mike and Ben came to visit this weekend, and we spent Sunday morning at Potato Creek State Park.

Along the trails, Lindsay found a small white and black-striped caterpillar with long, white hairs. The caterpillar was crawling on Canadian Clearweed (Pilea pumila). As you can see, Ben was excited to see this little creature.

I believe that this is a Hickory Tussock Moth caterpillar (Lophocampa caryae), but I don't see the long tufts of black hairs that are commonly found on this species. Hickory Tussock Moths feed on a variety of tree species, including hickory and pecan (Carya spp.), walnut (Juglans spp.), American Hornbeam (Carpinus caroliniana), ash (Fraxinus spp.), elm (Ulmus spp.), oak (Quercus spp.), and willow (Salix spp.). A rash can sometimes form on people who touch this caterpillar, and it has also been said to inflict a sting.

A bit later, Lindsay saw an Eastern Box Turtle (Terrapene carolina) with a beautifully patterned shell scurrying across the trail. The Eastern Box Turtle is one of only two turtle species in Indiana that spends most of its life outside of the water; the other is the Ornate Box Turtle (Terrapene ornata). Amazingly, there are records indicating that Eastern Box Turtles can live up to 120 years old! While this species is not uncommon, studies show that their numbers are decreasing as a result of habitat destruction and collecting.

Near the end of our walk, I spotted a large orange and black butterfly, and was able to get a few photos before it flew off. I think this is a Great Spangled Fritillary (Speyeria cybele), a common species of woodlands and meadows. Great Spangled Fritillary caterpillars overwinter, feed on violets (Viola spp.), and develop into an adult butterfly the following summer. They have been found alive until late September, making them a long-lived butterfly species.

02 August 2009

Weekend Insects

While botanizing this past weekend, I ran into an array of interesting insects, including one yellow jacket that wasn't too happy to be stuck under my shirt sleeve. Below are some photos of the more docile and cooperative species that I saw.

This gorgeous fluorescent blue and black-striped damselfly is in the group called bluets. The best that I can tell, this is a Tule Bluet (Enallagma carunculata). As always, help with identification, if I'm wrong, is much appreciated. This individual was observed at Merry Lea Environmental Center, close to Bear Lake, in Noble County, Indiana. Take a gander at the look he is giving me in the photo below. I think he's had enough of me chasing him around.

At the pannes north of Miller Woods in Lake County, Indiana, I saw the female Eastern Amberwing (Perithemis tenera) pictured below. This small, orange-tinged dragonfly, which is typically less than an inch long, can be confused for a wasp because of its size and the way that it moves in flight. Males of this species don't have the spotted wing pattern that the females do, but instead have solid amber-colored wings. Eastern Amberwings are most often found over lakes and ponds.

Also in one of the pannes, I ran into this crazy creature...

Ever seen anything like it? I sure hadn't. This white and black-checkered member of the long-horned beetle family is a Cottonwood Borer (Plectrodera scalator). The pattern on this beetle reminds me of a Rorschach inkblot test. Cottonwood Borers have a body that is over an inch and a half long, with spiny antennae that alone exceed that length! As the name implies, this species relies on Eastern Cottonwood (Populus deltoides), willows (Salix spp.), and other members of the willow family (Salicaceae) for multiple stages of its life cycle. In the photos above and below, the adult Cottonwood Borer is feeding on Bayberry Willow (Salix myricoides).

Have a close look at those mandibles. It's amazing that they only eat leaves and young twigs! After mating, the female lays eggs in pits at the base of a Salicaceous tree. The larvae hatch and burrow further into the tree, feeding as they go. This process can take up to two years. The larva then pupates in a root below ground, metamorphizes into an adult, and digs its way out from the ground. Because it doesn't leave from the tree itself, it leaves no exit hole in the tree.

With colorful insects that have life cycles like this, it's amazing I am still able to focus on the plants!