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.

White-whiskered Grasshopper

One of the most abundant, yet inconspicuous grasshoppers in North America is the little White-whiskered Grasshopper, Ageneotettix deorum. Easily overlooked as just another drab grasshopper, it can be easily recognized by its white antennae and red or orange hind tibia ("shin" segment on the hind leg).

This species is a member of the family Acrididae and the subfamily Gomphocerinae, known as slant-faced grasshoppers. The head of the White-whiskered Grasshopper is not as acutely sloped as its relatives, but it shares other subtle characters in common.

While most slant-faced grasshoppers are found clinging to grasses in the vertical plane, A. deorum is perhaps most often seen on the ground. When flushed from its hiding place it may leap into the middle of a trail where it could either hunker down, hop away again, or crawl rapidly into nearby grass tussocks. Only when it is walking do you easily see those bright red hind legs.

This is not a particularly large grasshopper, males ranging from 11-28 millimeters, female 15-28 millimeters. It is one of the few species in which both genders are nearly identical in size.

The White-whiskered Grasshopper occurs from the Great Lakes (Michigan, south and west to Indiana, Minnesota, and Illinois) through most of Missouri, western Arkansas, and Texas, all the way to the Pacific coast (southeast British Columbia, eastern Washington and Oregon, and much of California). Adult specimens can be found commonly from mid-July through early October.

Ageneotettix deorum frequents dry grasslands with short grasses, so I find it abundantly here in Colorado Springs on the fringe of the Great Plains. I still get confused periodically because of the variability of this species in terms of size and markings. Larger individuals can certainly be mistaken for grasshoppers of other genera. Other grasshoppers can have white antennae, and the White-whiskered Grasshopper can occasionally have darker antennae. The hind tibia is usually hidden under the edge of the hind femur when the insect is at rest, and there are simply few other consistent markings to go by.

The sheer abundance of this species puts it in the category of a rangeland and crop pest. During outbreaks there can be up to 25 adult specimens per square yard; and the species can account for fifty percent or more of the grasshopper fauna. Wheat is particularly vulnerable, but A. deorum also enjoys Kentucky Bluegrass and other kinds of music...I mean....forage. It will even feed on dried, fallen grassblades, seeds, dung, and deceased insects.

Eggs are laid in the soil in the summer and fall, hatching the following spring. Nymphs progress through five instars before reaching adulthood, roughly 40-48 days after emerging from the egg. The adults fly well, but flights are generally short (3-6 feet), and mere inches over the ground.

Sources: Bland, Roger G. 2003. The Orthoptera of Michigan. East Lansing: Michigan State University Extension Bulletin E-2815. 220 pp.
Capinera, John, L., Ralph D. Scott, and Thomas J. Walker. 2004. Field Guide to Grasshoppers, Katydids, and Crickets of the United States. Ithaca, New York: Comstock Publishing Associates (Cornell University Press). 249 pp.
Helfer, Jacques R. 1972. How to Know the Grasshoppers, Cockroaches, and Their Allies. Dubuque, Iowa: Wm. C. Brown Company Publishers. 359 pp.
Pfadt, Robert E. 1996. "Whitewhiskered Grasshopper," Wyoming Agricultural Experiment Station Bulletin 912

The Big-headed Grasshopper

It’s “OrThoptera Thursday” once again, and time for another grasshopper. My go-to place for grasshoppers here in Colorado Springs is a vast open space just up the street from my home. It is a shortgrass prairie in the literal sense in most spots, with extremely short, sparse turf in a mostly dusty, sandy, hilly plain that is dotted with scattered elm trees, sunflower, yucca, cacti, invasive weeds, and other low-growing herbs. This year it is even less lush.

Grasshoppers are usually abundant and diverse, but they are confined to only a few areas with herbs this year. Surprisingly, the dominant species I found yesterday was the Big-headed Grasshopper, Aulocara elliotti. It is technically one of the slant-faced grasshoppers, but it can easily be mistaken for one of the band-winged grasshoppers. It is easily identified by the very bright blue hind tibiae (“shin” segment on the hind leg), and large, rounded head.

I was still baffled initially, until I realized that last year I saw and photographed females, and what I was looking at yesterday were mostly males. One especially photogenic specimen, depicted here in the top- and bottom-most images, was also thermoregulating. Relying on camouflage and stillness is fine, unless the ground temperature is over 90° Fahrenheit like it was yesterday. Then you stand on tiptoe and even alternate which feet are in contact with the soil.

The Big-headed Grasshopper is fairly large as an adult, males ranging from 16-25 millimeters in length, females 22-35 millimeters. The species ranges across the entire western half of the U.S., north into the Prairie Provinces of Canada, and south well into central Mexico. While it prefers mostly shortgrass prairies and desert grasslands with sparse vegetation, I have encountered it at higher elevations (~8,500 feet) in coniferous woodlands. The adult insect can be found from June to September.

Nymphs emerge in mid-spring, having overwintered in the egg stage. They grow quickly, completing development to adulthood in 36-42 days. This may give them a head start in competing with other rangeland species. Males have only four instars (an instar is the period between molts), while females have five, so males mature sooner.

Aulocara elliotti feeds mostly on the green blades of grasses and sedges, but will also consume dry, cut grass, seeds, bran, and other ground litter it encounters while foraging. This species can occasionally reach pestiferous population levels and become damaging to crops and rangeland. Historical survey records show that it may reach densities of 20 specimens per square yard in mixedgrass prairie habitat, and up to 40 per square yard in desert grasslands. Not only does the feeding of the grasshoppers reduce available forage for livestock, but it can expose the soil to wind and water erosion.

The Big-headed Grasshopper is also capable of migrating, but apparently only for short distances. Observations in Arizona show that populations may move from one to seven miles in a season.

The continuing extreme drought in eastern Colorado would seem to guarantee that the Big-headed Grasshopper will continue to prosper while other species struggle. It will be interesting to follow the progress of this species in my neighborhood prairie patch.

Sources: Branson, David H. and Bethany Redlin (eds.). 2004. Grasshoppers: Their Biology, Identification, and Management (2nd Edition). US Department of Agriculture, Agricultural Research Service (PDF citation).
Capinera, John L., Ralph D. Scott, and Thomas J. Walker. 2004. Field Guide to Grasshoppers, Katydids, and Crickets of the United States. Ithaca: Comstock Publishing Associates (Cornell University Press). 249 pp.

Speckle-winged Grasshopper

It is “OrThoptera Thursday,” and time to introduce you to a common springtime grasshopper, the Speckle-winged Grasshopper. It goes by Arphia conspersa in scientific circles.

Ordinarily, I would be seeing fair numbers of this insect by now, and indeed they are slowly becoming more abundant as the weather warms from an unseasonably cold early spring here along the Front Range of Colorado. Warmer enclaves have more activity, such as around Pueblo and Cañon City. Last year I saw adults of this species on February 29, but then again we hardly had a winter.

Arphia conspersa is very widespread in its distribution, occurring from the Great Plains westward, north to central Alaska and south to central Mexico. It exploits a variety of habitats, from meadows up to 11,000 feet in elevation to desert canyons. Pastures, open fields, and vacant lots are where one is most apt to encounter it, even in highly urbanized areas.

Identifying the Speckle-winged Grasshopper can be surprisingly difficult because there is so much variation from one individual to the next. The overall color may be brown or grey with varying degrees of darker mottling. Many specimens sport a bright yellow “racing stripe” down the back when the wings are folded at rest. The tibia (“shin”) of the hind leg is often bright yellow (as can be the abdomen of males), but the tibia is usually concealed under the edge of the femur (“thigh”) unless the grasshopper is walking.

This species is one of the “band-winged grasshoppers,” named for the pattern on the hind wing. Unfurled, the hind wing is brightly-colored at the base, with a dark submarginal band across the outer reaches. The hind wing of Arphia conspersa may be colored yellow, orange, red, or even pink, but is only visible during the short flights made by the insect.

Males of the Speckle-winged Grasshopper are more likely to be heard than seen. Part of the courtship involves what are called “appetitive” or “crepitation” flights. The male purposely flies a short distance, making a loud crackling sound at will in the process. This visual and audible display apparently attracts the attention of the female.

A male can detect a female from a distance of at least two feet when both are on the ground. Considering how incredibly well camouflaged these insects are, that is no mean feat. He will approach by running, stopping and stridulating, and then repeating the process until he is next to his prospective mate. Stridulating is accomplished by rubbing the inside of the hind femur against ridges on the folded front wings. A faint chirping noise is generated by stridulating. Once in close proximity, the male orients to the female face-to-face, and they wave their antennae at each other. More complexities then ensue before she decides whether to accept his advances.

Mated females select patches of bare earth in which to lay their eggs. The abdomen of the female is capable of telescoping at least two inches while inserted into the ground. At that depth she deposits a pod of about twenty eggs.

female ovipositing in soil

Nymphs of Arphia conspersa begin hatching from the eggs in about mid-July, and go through a total of five instars (an instar is the period between molts) before reaching adulthood. The nymphs typically get to that fifth instar in late autumn, then overwinter. Exactly how they manage to survive is something of a mystery, but experiments have shown at least some specimens can withstand temperatures of -16°C for short periods.

nymphs

The fact that this is one of the few larger grasshoppers to be found as an adult in early spring makes its identification a bit easier. There are simply fewer similar species to confuse it with. Thankfully, this insect is never abundant enough to be a pest, either, even though it certainly consumes a fair amount of forage in the form of grasses and sedges.

Source: Branson, David, et al. 1994. “Speckle-winged Grasshopper, Arphia conspersa Scudder,” Wyoming Agricultural Experiment Station Bulletin 912.