"Arach" is Back!

One of the things I look forward to each autumn is the annual Flickr event known as "Arachtober". It is a Flickr group which slumbers between November and the following September, but remains a tradition among arachnophiles and macro photographers. There are always mesmerizing images posted from all corners of the globe.

Marbled Orbweaver, Kansas

Arachtober manages to recruit several new participants each year through word of mouth, blogs, and sheer curiosity. Not only spiders, but scorpions, ticks, mites, harvestmen, and all other arachnids are eligible for inclusion. Don't forget the artistry of spider webs, too, whether dew-adorned or dry.

Apache Jumping Spider male, Colorado

The only hard and fast rule of Arachtober is that the images you post to the group must not have appeared on your own Flickr photostream previously. Allowed quantity of images per day varies at the discretion of the group administrator.

Banded Garden Spider female, Colorado

Overall, interest in spiders seems to be increasing among the general public, and arachnids are achieving a much higher profile than ever before. This is great news, for there is still a great deal of work to be done to combat myth, superstition, misinformation, and fear.

Wolf spider, Alopecosa sp., Colorado

Please consider contributing to "Arachtober" on Flickr, or find another way to dedicate some time to sharing your spider observations, questions, or images. There are many groups on Facebook devoted to spiders and their identification, for example; and presumably, the same applies to Instagram. There is much you can contribute to our collective knowledge by doing so. Thank you.

Grasshopper or Locust?

A person on a Facebook insect identification group recently asked a very good question about the difference between a grasshopper and a locust. You would think it is pretty straightforward, but not so fast.

The American Bird Grasshopper, Schistocerca americana, is related to some grasshopper species in Europe and Africa that can become locusts; and it sometimes migrates beyond its usual geographic range in the U.S.

Most of us think of locusts in the context of Biblical plagues in Africa and parts of Europe, in ancient times. Such plagues still happen, and they are almost apocalyptic in their destructiveness. They even occur in North America on occasion, as well as other parts of the world, so there must be more than one species of locust, right? Yes, and no.

Two-striped Grasshopper, Melanoplus bivittatus, has been overwhelmingly abundant in recent years along the Colorado Front Range

Locusts are not a species of grasshopper, they are the result of overcrowding in the nymph stage of many kinds of grasshoppers. Under favorable conditions, there is an extraordinary survival rate of young grasshoppers, which are called nymphs. When they are literally so abundant and concentrated that they are rubbing elbows (well, "knees" is probably a more appropriate term), this friction causes them to detour from their normal route of metamorphosis.

Instead of maturing into the usual grasshopper, the adult stage features longer wings and other body modifications that permit them to fly greater distances, remain airborne for longer periods, and to undertake these migrations from one food source to the next over long distances. They also may be aided by winds ahead of storm fronts.

The Clear-winged Grasshopper, Camnula pellucida, is prone to population outbreaks in the American West

This is something of a simplification of the physiology of locusts versus normal grasshoppers, but a surprising number of species have the potential to morph into locusts when conditions are right. Then they overwhelm the landscape, defoliating every plant in their path.

Locust swarms will devour plants they would not normally eat. I recall a presentation about a locust epidemic in Oregon where the scientist showed slides of juniper trees (yes, juniper trees) that had been reduced to skeletons by grasshopper swarms. The locusts have even been known to eat garments on clotheslines. Grasshoppers are also omnivores, and will not hesitate to eat dead members of their own species, or gnaw on injured or even healthy ones. It is late in grasshopper season here now in Colorado, and I regularly see grasshoppers with wings reduced to stubs thanks to hungry comrades.

A victim of the grasshopper-killing fungus Entomophaga grylli

Fortunately, for us at least, grasshoppers face many mortality factors. While it has been a banner year for grasshoppers this year along the Colorado Front Range, huge numbers have succumbed to the entomopathic fungus Entomophaga grylli. The insidious fungus grows inside the insect, eventually commandeering its brain and forcing it to behave abnormally. The grasshopper, through no will of its own, climbs to the top of a tall weed, assumes a death grip embracing the stem, and dies. The fungal spores then erupt and rain down on healthy grasshoppers below to begin the cycle again. The spores may even decapitate the dead grasshopper as they exit.

Grasshoppers are the chief grazers of the prairie, even more impactful than livestock, deer, pronghorn, elk, and bison. Natural rangeland can usually withstand their feeding, but ranchers obviously see them as competition and exercise chemical controls when necessary. Since grasshoppers are mostly generalist feeders (a few specialize on only certain broadleaved plants), they pose a threat to agricultural crops, too.

A specimen of the extinct Rocky Mountain Locust
© Bugguide.net

Ironically, the Rocky Mountain Locust, Melanoplus spretus, once the most abundant and devastaging insect pests ever to occur in North America, is now extinct. The book Locust, by Jeffrey A. Lockwood, chronicles the rise and dramatic fall of the species, which ultimately vanished from the U.S. landscape by the early 1900s. I will not spoil the solving of the mystery, as Lockwood's account is far more riveting than anything I could craft if I was even prone to writing historical fiction. Let us just say it is a cautionary tale.

Historical range of the Rocky Mountain Locust

We can certainly be grateful that we seldom experience such traumatic explosions of grasshoppers here on American soil, but we should be empathetic to other nations that do. Entire economies can be on the verge of collapse in the wake of such devastation.

Source: Lockwood, Jeffrey A. 2004. Locust. New York: Basic Books (A member of the Perseus Books Group). 294 pp.

A Funny Story

More content will be coming to this blog, more regularly, in October, but I wanted to share a humorous experience from our last bioblitz at Ute Valley Park in Colorado Springs. It was Saturday morning, September 16, and I'd already been up earlier than I usually am, so I will blame my assumptions on being a little tired.

I happened to spot an interesting syrphid fly, Ferdinandea sp., right in the middle of the trail. The park gets a lot of foot and mountain bike traffic, so I hurried to take pictures. My camera was not focusing well on this mostly overcast day, so I maneuvered to the side of the trail and kept trying....

Sure enough, I heard a trail runner pounding down the trail, and then stopping abruptly. I thought that was quite considerate and polite, but I hurried even faster to get a respectable image. I said "thank you for stopping" to the obliging jogger, but there was no reply. I finished shooting, and turned to continue on the trail. When I looked up, this was the "trail runner."

Naturally, when I related this story to others back at base camp, everyone had to offer their own punchlines. "But what did the buck say?" in reference to the song "The Fox" (What Does the Fox Say? "No, the buck stopped there," punned another individual. Yeah, yeah, hilarious.

I do not intend to be quite so assuming in the future, lest the next trail runner be a bobcat, mountain lion, coyote, or bear. Even our urban neighborhoods here can be dangerous to those who are not aware of their surroundings. Happy trails, folks.

Ammophila nigricans Revisited

I wrote about this species back in December, 2010 when I had only one image of a sleeping female in South Deerfield, Massachusetts on July 5, 2009. Recently, I had the privilege of imaging another female in Leavenworth, Kansas, on August 24.

These are large, beautiful insects, velvety gun-metal blue with a red band across the abdomen, and black wings. It can be confused with no other member of the genus Ammophila. This particular specimen spent the night in a patch of weeds and flowering mint, eventually waking up to visit many mint blossoms for nectar. This wasp is known to visit many kinds of flowers, in Illinois at least. I collected one specimen from Swamp Milkweed in Cincinnati, Ohio.

Females need to fuel themselves so as to be able to carry out the tasks of providing for their offspring. Each wasp is solitary, digging her own vertical or angled burrow in clayey or sandy soil, terminating in a horizontal chamber at the bottom. Once the nest is excavated, it is off to find a large caterpillar. Known hosts include the larvae of underwing moths (Catocala spp.), the locust underwing (Euparthenos nubilis), and zale moths (genus Zale). Those are hefty caterpillars, but then they are destined to feed the larva of a very robust wasp.

This YouTube video may or may not depict A. nigricans, but the searching behavior must be very similar at the least. The female wasp is not likely to locate a caterpillar based on movement or color, as the caterpillars are very cryptic and usually resting stock still, feeding at night to avoid predators like the wasp. So, she must find her prey by touch.

Ammophila nigricans ranges over the entire eastern United States, from Kansas and Texas to New England, and south to Georgia, Florida, and Louisiana. It does not appear to be nearly as common as most other members of its genus, so I consider myself lucky to have had a few hours observing this one specimen.

SourcesDiscover Life
Krombein, Karl V. and Paul D. Hurd, Jr. 1979. Catalog of Hymenoptera in America North of Mexico vol. 2 Apocrita (Aculeata). pp. 1199-2209.