Orthoptera Thursday: The Katydid's Menu

Carnivorous katydids? That might come as a shock, but in reality, many members of the order Orthoptera, which includes katydids, grasshoppers, and crickets, are omnivorous to at least some degree. This broad diet is one reason these insects are so successful. Let’s take a closer look at one subset of katydids in particular.

A female Orchelimum sp. meadow katydid.

Katydids are also known as longhorned grasshoppers, for their exceptionally long, thread-like antennae, in contrast to true grasshoppers that have shorter, thicker antennae. Katydids are in the family Tettigoniidae. Most katydids are green, brown, or gray in color, though tropical species can be stunningly colorful.

Meadow katydids and conehead katydids form the subfamily Conocephalinae. They are among the most abundant of orthopterans in the eastern United States and adjacent Canada. At this time of year they have reached maturity and are seeking mates. Taking a stroll through tall grass, especially in wetlands, lush meadows, or prairies will flush countless individuals.

A female conehead katdid, Neoconocephalus sp.

A substantial portion of the diet for these katydids is grass seeds, and they have mandibles (jaws) powerful enough to crack them. Conehead katydids are the largest, some members of the gens Neoconocephalus exceeding seven centimeters (nearly three inches). I can tell you from personal experience that you do not want to get bitten by one of them.

A male conehead katydid peers from dense grass.

Meadow katydids and coneheads also feed on forbs, defined as any flowering herbaceous plant that is not a grass, sedge, or rush. The insects feed on the leaves and flowers of those plants.

The impact of katydids on plant communities is not negligible. One study revealed that a population of three meadow katydid species turned nearly 16% of the biomass of a rush species (Juncus) into katydid biomass (Parsons and de la Cruz, 1980).. Damage to seeds developing in flowers resulted in a 30-50% decrease in in seed production of rushes and grasses, too.

A female lesser meadow katydid, Conocephalus sp., feeds herself a grass seed.

Watching a katydid eat is a delightful experience. They are surprisingly nimble, and will use their front tarsi (the “feet” on their front legs) like hands to direct the morsel into their mouths. It is very much like any mammal feeding itself, using its paws.

A male Orchelimum eating an acanoloniid planthopper.

Plant matter has relatively little protein and fat, so those compounds need to come from elsewhere for a katydid to prosper. Consequently, some species, especially the meadow katydids, have evolved to become opportunistic predators on other insects, especially if those insects are injured.

The insects usually encountered by katydids are other species that are herbivorous in the same habitats occupied by the katydids. This includes leafhoppers, planthoppers, and even smaller katydids.

A female Orchelimum feeding on a female smaller meadow katydid, Conocephalus sp. The victim had just mated.

Female katydids need extra protein to nourish the development of eggs, and they get a surprising assist from males. During copulation, the male delivers a sperm packet called a spermatophore. The spermatophore consists of the sperm container (ampulla) and a gelatinous mass called a spermatophylax. This is an expensive gift for the male to produce, but it is less likely that a female will mate again once she is provided this nutritious investment. This is especially true for larger meadow katydids, genus Orchelimum.

The spermatophylax consists of protein, water, some carbohydrates, but few lipids (fatty acids). The female consumes this after mating occurs, along with the rest of the spermatorphore, which protrudes from her genital tract after its insertion by the male.

A pair of meadow katydids, Orchelimum sp., just beginning to mate.

The spermatophore is perhaps one step away from sacrificing yourself entirely to your mate. Science weighs the concrete costs and benefits of such transactions, but perhaps something more meaningful is lost in the translation. The more we learn about the insect nervous system, the shorter the distance between “them” and “us.”

The jelly-like spermatophore forming where the pair are joined.

Sources:Gwynne, Darryl T. 2001. Katydids and Bush-Crickets: Reproductive Behavior and Evolution of the Tettigoniidae. Ithaca: Cornell University Press (Comstock Publishing Associates). 317 pp.
Parsons, K.A., and A.A. de la Cruz. 1980. “Energy flow and grazing behavior of conocephaline grasshoppers in a Juncus roemerianus marsh,” Ecology 61: 1045-1050.
Thornhill, Randy and John Alcock. 1983. The Evolution of Insect Mating Systems. Cambridge: Harvard University Press. 547 pp.

OrThoptera Thursday: Eastern Ant Cricket

Between allergies to grass pollen, windy and/or stormy weather, and periodic depression, I have not been getting out in the field very often lately. Consequently, I was delighted when an unusual insect came to me. Leaving our bathroom for our bedroom the other night, I caught movement out of the corner of my eye. A small insect was running along the edge of the bathtub. My initial thought was "oh, shoot, a cockroach nymph." Closer examination revealed it to be something much more exciting and not at all a pest.

It was an adult male Eastern Ant Cricket, Myrmecophilus pergandei. How it came to be in our bathroom I have no idea. This species, like others in its genus, is supposed to be found almost exclusively in association with ants. Ironically, ants may consider these diminutive crickets to be pests inside their colonies.

Myrmecophilus have been observed actively "licking" ants, and the walls of underground ant nests, presumably feeding on oily secretions from their hosts' exoskeletons. The ants barely tolerate this unwanted attention, and may attack or even kill and eat the crickets. Still, the cricketes are remarkably agile, able to run away quickly from danger. I was surprised that I managed to successfully usher this one into a vial so I could take better images in the casserole dish that is our "studio" for insect and spider subjects.

Carpenter ant, a potential host species for our ant cricket

Ant crickets vary in size, usually in accordance with the host ant species, but none exceed 4.7 millimeters. The smallest adult specimens recorded measured less than 1.5 millimeters.The one imaged here is a relative giant. I suspect it may have come from a nest of carpenter ants, of which we have several around our home, one satellite nest in the frame of our back door, not terribly far from the exterior wall of the bathroom.

Among their adaptations to life in subterranean ant colonies, ant crickets have no ocelli (simple eyes), and their compound eyes are reduced to a small collection of facets. What they lack in vision they make up for with long, sensitive antennae. They also have oversized cerci, the pair of flared, tail-like appendages at the rear of the abdomen. The cerci are covered in sensory hairs that, as in roaches, other crickets, and related orthopterans, detect otherwise imperceptible air currents generated by approaching predators.

Eastern Ant Cricket is found from Maryland south to Florida, and west to southern Iowa, eastern Kansas, Oklahoma, and Texas, but there are recent records from New York and New England. There may be other species where you live. Oregon Ant Cricket, Myrmecophilus oregonensis, ranges west of the Cascade Mountains from southern British Columbia through Oregon and Washington, and most of California. Mann's Ant Cricket, M. manni, has a similar range, but from southern Washington state through Oregon, California, most of Nevada, and Arizona. Nebraska Ant Cricket, M. nebrascensis, occurs from southern California to Texas, and north through eastern Colorado, and most of Nebraska, Kansas, and Oklahoma.

Sources: 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: Cornell University Press. 249 pp.
Bugguide

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.

The Great Grasshopper Hunt II

I am terribly behind in chronicling field experiences I have participated in this summer, including the second annual(?) "grasshopper hunt" co-sponsored by Mile High Bug Club and the Aiken Audubon Society. Our first one was held last year at Homestead Ranch Regional Park near Peyton, Colorado. This time we opted to head farther south and a little farther east to Chico Basin Ranch; and we were led by grasshopper expert Bill Maynard.

Our intrepid participants © Bell Mead

The ranch is a sprawling 87,000 acres that straddles the El Paso and Pueblo County line. Its wide array of habitats, from sandhills to artificial wetlands, makes for high biodiversity, especially among insects and grasshoppers in particular. In only a few hours our party of roughly ten people observed forty (40) species of grasshoppers, plus many other insects and arachnids.

Pink form of the Broad-banded Grasshopper, Trimerotropis latifasciata

Bill is rather new to the study of grasshoppers, but he quickly masters many aspects of natural history. He is already recognized as a leading authority on birds and dragonflies, with many state and county records to his credit. It is only a matter of time before the same can be said of his expertise in the order Orthoptera to which grasshoppers belong.

Rather than overwhelming you with images here, I will direct you to the Mile High Bug Club Flickr Group where you can peruse the image collection at your leisure.

Snakeweed Grasshopper, Hesperotettix viridis

We would be remiss if we did not also acknowledge the hospitality of the Chico Basin Ranch staff, especially Tess Leach and her family. Her two children were especially curious, and remarkably patient and gentle in their approach to the many grasshoppers we saw.

Three-banded Grasshopper, Hadrotettix triafasciatus (foreground), signaling to a Broad-banded Grasshopper (background) to get out of its territory

The intense heat of that August 6 day sent some members of our party packing by about noon, but who could blame them? The Plains Harvestfly, a type of cicada, made it seem hotter still with its loud, oppressive buzz. All in all, the "expedition" was a resounding success, and no vehicles or people were injured during the odyssey.

Plains Harvestfly, Neotibicen dealbatus

While plains and deserts are prime habitats for grasshoppers, you can find them nearly everywhere. You will be surprised by the number of species you can discover in your own backyard, neighborhood park, vacant lot, or any other patch of wildness. Even now, with the first frosts approaching, grasshoppers are among the few insects left in any abundance. Go take a look for them.

Tree Cricket Courtship

Tree crickets, genus Oecanthus, are having quite the year here along the Colorado Front Range. Last month I went to Garden of the Gods park in Colorado Springs and could hardly go twenty feet without hearing a male tree cricket singing in the tall weeds or from a yucca blade. I even managed to capture videos of their singing and courtship.

Male tree cricket singing

There are five species of tree crickets in Colorado: the Prairie Tree Cricket, Oecanthus argentinus, Western Tree Cricket, O. californicus, Snowy Tree Cricket, O. fultoni, Black-horned Tree Cricket, O. nigricornis, and the Four-spotted Tree Cricket, O. quadripunctatus. Determining the species of a given individual is difficult to say the least because identification frequently hinges on the markings present (or absent) on the first two segments at the base of the antenna. I know! The whole insect is only about twenty millimeters maximum.

It is much easier to tell which gender is which. Females are very slender, with the front pair of wings hugging the body tightly. The short, stout ovipositor, used to insert eggs into berry canes and other plant stems, is easily visible.

Female tree cricket

Males on the other hand have the front wings greatly expanded into paddle-shaped musical instruments that make them look more like green lacewings than crickets. The intricate pattern of veins is all about lending support to the membrane that generates, amplifies, and projects the male's song. He lifts his wings into a heart shape at a 90-degree angle to his body in order to sing.

Tree cricket singing

The song is produced when a "scraper" on one wing is drawn across a "file" on the other wing, near where the wings join the thorax. The rapidity with which this happens cannot be captured by ordinary video cameras. Some male tree crickets align their wings with gaps in foliage, or even chew holes in leaves, to reduce acoustic interference and further intensify their call.

Singing male tree cricket with exposed metanotal gland in center of thorax

Like most crickets and other members of the order Orthoptera (grasshoppers, katydids, crickets), males have more than one kind of song. Once a male successfully lures a female, he switches to a softer song to help her orient to him. His raised front wings also expose a metanotal gland in the center of his thorax, which secretes a substance that the female feeds on. This is something of a distraction so that he can transfer a spermatophore, or "sperm packet" to her genital opening. The packet appears as a small, pearly blob near the tip of her abdomen in the video and images below.

Female tree cricket feeding from male's metanotal gland

The spermatophore takes time to drain sperm into her oviduct, and the female would undoubtedly eat it if she did not have the more attractive metanotal secretion to lick instead. She is sufficiently addicted that she feeds for several minutes after mating.

Tree crickets are omnivores, feeding on plants and small insects like aphids. Some species are truly arboreal, living in shrubs or high in trees, but a surprising diversity can be found in grassy fields, meadows, and similar habitats.

Male tree cricket at rest

There are many wonderful online resources to help you appreciate and identify tree crickets. One of the best is Singing Insects of North America, which covers grasshoppers, katydids, and cicadas along with crickets. Oecanthinae.com was created by Nancy Collins, a citizen scientist who has become a leading authority on tree crickets, even discovering a species new to science. Lisa Rainsong writes and illustrates the blog "Listening in Nature," which covers all kinds of acoustic phenomenon in the outdoors.

Male Prairie(?) Tree Cricket singing

Enjoy listening to, and looking for, tree crickets in your own neighborhood. Finding them is a challenge, but your patience will be rewarded. Above all, have fun.

Sources: Collins, Nancy. 2014. All About Tree Crickets. Parker, Colorado: Outskirts Press. 48 pp.
Dethier, Vincent G. 1992. Crickets and Katydids, Concerts and Solos. Cambridge, Massachusetts: Harvard University Press. 140 pp.
Elliott, Lang and Wil Hershberger. 2007. The Songs of Insects. Boston: Houghton Mifflin Company. 228 pp.

The Grasshopper Hunt

The Aiken Audubon Society here in Colorado Springs asked me to speak at their September monthly meeting, and to lead a field trip beforehand. I chose the topic of grasshoppers since there is so much diversity here. The field trip was to Homestead Ranch Regional Park near Peyton, Colorado (El Paso County). I was surprised and delighted by the turnout, and the interesting animals we encountered.

Carolina Grasshopper basking

We were fortunate to have two young men, Seth and Zach Vogel, and their father, Tim, along for the trip. The boys helped find many more animals than we would have were we left to my own devices. They have a keen eye, endless stamina, and great enthusiasm. Tim employed a GoPro® camera to record parts of the expedition in this video.

© Tim Vogel

The Mile High Bug Club was represented by Bell Mead and myself; and Aiken Audubon by Jeannie Mitchell, Leslie Holzmann, and Bill Maynard. Alison Kondler even came down from the Denver area. Thankfully, the weather was sunny, but not too hot.

Plains Lubber grasshopper

We had not even made it beyond the playground and picnic shelter before we saw Carolina Grasshoppers basking on the pavement, and the boys had found an enormous Plains Lubber Grasshopper, Brachystola magna. The latter brought out the "'hopper-razzi," cameras clicking away.

Plains Lubber grasshopper draws a crowd

Further along the trail through grassy habitat on a gentle slope, we encountered several species of spur-throated grasshoppers in the genus Melanoplus, plus Pallid-winged Grasshoppers (Trimerotropis pallidipennis), and the Northwestern Red-winged Grasshopper, Arphia pseudonietana.

While I was explaining how to identify a particular species, the boys brought over a really nice find: a male Mormon "Cricket." The Mormon Cricket, Anabrus simplex, is not a true cricket, nor a grasshopper, but a kind of shield-backed katydid.

Mormon "Cricket" male

Seth and Zach located these large insects by homing in on their "song," a kind of buzzing sound produced by the males rapidly rubbing their short wings together.

We entered a narrow zone of pine trees near the summit of the slope we were traversing, and that brought us another species of grasshopper, apparently confined to that wooded habitat. The Kiowa Grasshopper, Trachyrhachys kiowa, is another of the "band-winged grasshoppers" named for the dark band on the colored hind wing. The hind wings are only visible when the insect flies, and most grasshoppers fly only short distances before landing and once again becoming nearly invisible owing to their superb camouflage.

Kiowa Grasshopper with hind wing spread

Band-winged grasshoppers can make noise in flight. This is called "crepitation," and is a rattling or crackling sound, presumably as front and hind wing rub together....but the sound can be produced at will, so it is something of a mystery how it is produced.

The hill terminates in a rolling plateau, and the grassland changes a bit in composition. Here we heard slant-faced grasshoppers, hidden from view. Slant-faced grasshoppers cling to vegetation in the vertical plane rather than crawling on the ground like band-winged grasshoppers usually do. They produce sound not by crepitation but by "stridulation." The male grasshopper rubs the inside surface of his hind femur ("thigh") against veins of the folded front wing. The result is a "zip-zip-zip" kind of song.

We ended our hike at a circular water trough for horses and cattle, fed by a well with a windmill pump. The water looked awful, but was full of life. It took no time at all for Zach to spy a Barred Tiger Salamander (Ambystoma mavortium), one of at least two inhabiting the pool.

Barred Tiger Salamander

There were also water striders (insect family Gerridae), backswimmers (Notonectidae), diving beetles (Dytiscidae), and a Giant Water Scavenger Beetle, Hydrophilus triangularis (family Hydrophilidae). Various dragonflies circled as well.

Giant Water Scavenger Beetle

Everyone appeared delighted by the whole adventure, and I am very happy to see what is apparently a growing demand for field outings geared to organisms other than birds, or at least in addition to birds. I would very much like to do more of this kind of thing, all over the U.S., so keep those invitations coming!

How Insects Sing

Observing the insect world requires one to use not just their vision, but their hearing, too. Many insects use sound to communicate with each other, or to ward-off enemies by startling them with a sudden, audible noise. How do insects make such a racket, anyway?

Male field cricket, Gryllus sp., Arizona

Stridulation

Most insects produce sound by rubbing one body part against another, a phenomenon known as "stridulation." The most accomplished stridulators are, of course, the members of the order Orthoptera. Most male grasshoppers, katydids, and crickets have modifications of the body that allow them to create, amplify, and broadcast auditory signals to attract mates and/or ward-off competing males.

Male larger meadow katydid, Orchelimum sp., singing in Nebraska

Short-horned grasshoppers in the family Acrididae rub special pegs on the inside surface of the hind femur ("thigh") against raised veins on the front wings while the insects are at rest. Slant-faced grasshoppers (subfamily Gomphicerinae) are especially accomplished at this and their soft zip-zip-zip songs are easily heard during daylight hours. Below is a video of a male Psoloessa grasshopper stridulating vigorously. Unfortunately, the incessant prairie winds on the eastern Colorado plains overwhelm the 'hopper's song.

Male Psoloessa sp. grasshopper stridulating

Band-winged grasshoppers (subfamily Oedipodinae) also stridulate, but not as loudly. You are more apt to see two males sizing each other up instead of a male courting a female. In the video below, two male Carolina Grasshoppers stridulate aggressively, side-by-side, until the loser leaves the stage.

Male Carolina Grasshoppers, Dissosteira carolina, stridulating aggressively

Katydids and crickets are the most accomplished of all stridulating insects, in part because the wings of the male insect are highly modified to produce sound; and the insect often stations itself in a circumstance that enhances the projection of sound, such as the mouth of a burrow, or between leaves.

Male tree cricket, Oecanthus sp., singing, Colorado

Male tree cricket at rest

Most male katydids are "left-handed," meaning that the left forewing overlaps the right forewingwing. Contrastingly, most male crickets are "right-handed." In both cases, the edge of one wing is equipped with a "file" of fine teeth, while the other wing has a bladelike "scraper" that is drawn rapidly over the file to create the song.

Singing male field cricket, Gryllus sp., Colorado

The songs we hear most often are "calling songs" designed to attract females; but, crickets in particular produce two other types of songs: a "rivalry song" that is directed at another male during and/or after a confrontation, and a soft "courtship song" to entice a female into mating.

Male Drumming Katydid, Meconema thalassinum, Ohio

Percussion

A surprising variety of insects, from treehoppers to stoneflies, to beetles actually smack body parts against a substrate such as a leaf or twig to generate vibrations that are received by potential mates. Sometimes these body-slamming signals are also audible. The Drumming Katydid, Meconema thalassinum, and "wing-tapper" cicadas in the genus Platypedia do not produce sound the way most other members of their clan do. Instead, they strike a blow against a branch, leaf, or twig to call to the opposite sex. This is still audible to us, too.

Wing-tapper cicada, Platypedia putnami, Colorado

Males of most cicada species have a pair of built-in percussion instruments. Large pits take up most of the volume of the abdomen and are covered by "lids" called opercula (singular: operculum). Inside each chamber, a strong muscle pulls and releases another organ called a tymbal. The tymbal buckles under the muscle's tug, generating a noise, then snaps back when the muscle relaxes, making another noise. The muscle twitches at such a high rate that we hear one continuous sound, and a very loud one at that.

Underside of male Tibicen sp. cicada showing operculum

Hearing

How do the insects hear each other? Insects do not have ears, per se, but they do have auditory receptors called typmana located in peculiar places. Short-horned grasshoppers have an opening on each side of the abdomen, near the base. Cidadas likewise have their typana located in the front section of the abdomen. Katydids and crickets have a slit located on the front surface of the tibia ("shin") on each front leg. The tympana is usually represented as a thin, oval membrane located inside the "ear" opening.

Greater Anglewing Katydid, Microcentrum rhombifolium, showing "ear"

Resources

Many singing insects can be identified reliably only by differences in their songs, so it helps to familiarize yourself with their calls. Thankfully, a variety of resources are available to do just that. The "Singing Insects of North America" website is particularly useful. Examples of songs are available as audio files for most species.

Male conehead katydid, Neoconocephalus ensiger, singing, Massachusetts

Lisa Rainsong's superb scientific blog "Listening in Nature" covers bird songs, frog choruses, and other sounds of nature as well as insect songs.

Several books exist that address insect songs, but my two favorites are The Songs of Insects by Lang Elliott and Wil Hershberger (2007, Houghton Mifflin Company), and Crickets and Katydids, Concerts and Solos, by Vincent G. Dethier (1992, Harvard University Press).

You should be hearing field crickets any time now, if you aren't already, along with the daytime calls of some acridid grasshoppers. Enjoy the symphony.

Insidious Insect Fungi

The Walking Dead is a popular television show these days, but reality is perhaps even more sinister. Did you know that there are fungi that hijack the brains of insects causing them to behave in ways that benefit the fungus? It's true, and you have probably seen evidence of this macabre life cycle without knowing the answer to the mystery.

Fly infected with fungus attached to a leaf (Massachusetts)

Cheryl Harner, a naturalist and writer at Weedpicker's Journal, asked me about this bizarre phenomenon a couple of years ago, and I always meant to learn more about it myself. You owe it to yourself to check out her blog, and I'll try to complement her post rather than compete with it. She did an excellent job of researching and linking, though.

Dead grasshopper nymph that has climbed a grass stem due to funal infection (Massachusetts)

It is not just grasshoppers and ants that are victimized by what are called "entomopathic" fungi. Flies are among the most conspicuous of hosts. You have probably seen flies clinging to foliage or twigs in odd, contorted positions, with bloated abdomens. The spores of the Entomophthora muscae fungus have their hosts literally bursting at the seams, the membranes between the abdominal segments.

Meanwhile, grasshoppers and related orthopterans are plagued by Entomognatha grylli, and lady beetles are often afflicted with Laboulbeniales fungi.

The life cycle of fungi in the order Entomophthorales begins when a spore lands upon an insect. However, many of the fungi are very host-specific, so if a spore lands on the "wrong" bug it is likely done for. Should the spore contact the correct host, it soon germinates, penetrating the cuticle of the insect and growing internally, absorbing the host's nutrients, eventually killing it. Before the doomed creature perishes, the fungus does something remarkable. In many cases it stimulates the host to seek a high point, either by climbing or flying, whether or not the insect normally performs such behavior. This phenomenon is sometimes referred to as "summit disease."

Headless grasshopper corpse in wake of fungal infection (Colorado)

Once the host insect ascends a grass stem, for example, the fungus sends out special structures called rhizoids that are white, thread-like filaments. These fibers often emerge from the insect's tarsi ("feet") or mouthparts, anchoring the bug to the substrate such that it is not easily dislodged after death. Now the spores erupt, sometimes in the form of fruiting bodies like other fungi, or simply exuding from holes in the host's cuticle.

Carolina Leafroller ("cricket") showing fungal rhizoids penetrating its feet and anchoring it to the leaf (Ohio)

Grasshoppers are among the most conspicuous victims if only because of their size, but most types of insects, and spiders, too, are vulnerable to fungal infection. The typical appearance of fungus victims are stiff, dessicated specimens that are essentially mummified.

Harmonia axyridis with perithecia of Hesperomyces virescens at the tip of its wingcovers (elytra)

Fungi in the order Laboulbeniales affect beetles in particular, and are very different in their mode of dispersal and effect on the host. Hesperomyces virescens apparently afflicts only the Multicolored Asian Lady Beetle, Harmonia axyridis, at least here in North America. It is microscopic, and is essentially a sexually transmitted disease since the overwhelming means of infection occurs during mating of the host. Spores can also transfer when large groups of overwintering lady beetles force the insects to rub against each other.

Mating pair of Harmonia axyridis in Illinois exhibiting symtoms of Hesperomyces virescens

Most adult beetles exhibit symptoms in the form of tiny, yellow, scale- or flake-like protrusions from the cuticle, especially at the tip of an elytron (wing cover). These are the fruiting bodies, called perithecia, from which spores are issued, if I comprehend the literature and language of mycology correctly. Interestingly, the fungus has little or no effect on the host, but depends on it for reproduction.

When one thinks of mortality factors that affect insects, or most other animals, we tend to forget the impact of fungal organisms. Maybe I have seen one too many episodes of the television show Monsters Inside Me, but I have a whole new respect for fungi now. It helps to remember that fungi are often very host-specific, so handling a fungus-ridden bug is not going to pose a health threat to a human. As far as we know.

Fungus-infected fly corpse on leaf (Colorado)

Sources: Eiseman, Charley and Noah Charney. 2010. Tracks & Signs of Insects and other Invertebrates. Mechanicsburg, Pennsylvania: Stackpole Books. 582 pp.
Parker, Abigail M., et al. 2010. "with Labioulbeniales fungus," Bugguide.net.