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.

Fork-tailed Bush Katydid

I vividly recall an episode in my childhood that perhaps cemented my fascination with insects. I must have been somewhere between eight and eleven years old. One afternoon in late summer I heard an insect calling at regular intervals from a rhododendron bush outside the front door of our Portland, Oregon home. I finally tracked down the creature and discovered it was a male Fork-tailed Bush Katydid, Scudderia furcata. What happened next I shall relate later in this post.

I did not know at the time what kind of katydid I was observing. Years later I discovered E. O. Essig’s book Insects of Western North America in our public library and found the species there. Indeed, it was virtually the only option for western Oregon, Washington, and southern British Columbia.

Eight species of bush katydids in the genus Scudderia are now recognized in the United States and southern Canada. The Fork-tailed Bush Katydid is by far the most widespread, being transcontinental in its geographic distribution. Still, in most regions it is next to impossible to separate from other species.

The only reliable way to differentiate Scudderia species is by the shape of the “dorsal process” or “supra-anal plate” in adult male specimens. This horn-like feature juts out of the top of the abdomen at the rear. Another structure, the “sub-genital plate” curves up from below to meet the supra-anal plate. The sub-genital plate may at first be mistaken for an ovipositor, an organ found only in female katydids.

Not surprisingly, the shape of the dorsal process in the Fork-tailed Bush Katydid is, well, fork-like. It looks like a miniature tuning fork, as revealed in the image above. Images of wild, living male bush katydids are usually impossible to identify to species because the folded wings usually conceal the supra-anal plate.

Males also possess the “file and scraper” modifications on the “shoulders” of their front wings. These are the structures they rub together quickly to produce songs. Bush katydids typically rasp a short, intermittent call: s-s-s-s-s-S-S-S-T. This discontinuous song no doubt helps prevent predators from pinpointing the location of the insect.

Back to the opening story. I saw the male katydid produce its song, and in short order a female flew in to join him. Both genders, once close to each other, will talk in soft “ticks,” but I do not recall them having such a conversation. The next thing I knew, the two were in copula, “tail-to-tail.” I watched in horror as I saw a white, gelatinous mass oozing from between the two. When they finally separated, it appeared the female had been torn open and was losing her innards.

I learned much later in my life that the male was the source of this mass. Male katydids and related orthopterans transfer a protein-rich spermatophore in the process of inseminating a female. She consumes this object while the male’s sperm enter her oviduct.

Scudderia sp. female

Fertilized female bush katydids use their curved, knife-like ovipositors to insert eggs between the layers of a leaf, at the leaf’s edge. The result is a kidney bean-shaped bulge in the leaf. A female can lay up to 175 eggs, but deposits a small quantity at each location. The following spring, a tiny katydid emerges from each egg.

Scudderia sp. nymph

Nymphs go through six instars (an instar being the interval between molts), gradually accruing wing pads and both internal and external reproductive organs. They are general feeders on the foliage of shrubs. They are sometimes considered a pest in orchards and citrus groves when populations build to high levels (Bentley, 2002 and Headrick, 2000).

Adult S. furcata are 36-40 millimeters from the head to the tips of the folded wings, so they are not small insects. Still, they are incredibly well camouflaged. Most specimens are wholly green, but late-autumn specimens are correspondingly brownish, reddish, or even pink. They are most active at night, and are sometimes drawn to outdoor lights. Both sexes fly well.

Katydids in general are among my favorite insects, and I can’t help but wonder if that mating pair forever endeared them to me. Keep a listen for katydids in your own yard, garden, or neighborhood park. See if you can tell different species apart by their songs. Search with a flashlight and you will eventually find one of these amazing insects.

Sources: Bentley, Walt. 2002. “Researching Biology and Control of Forktailed Bush Katydid (Scudderia furcata Brenner) and Western Spotted Cucumber Beetle (Diabrotica undecimpunctata howardi Barber) in Stone Fruits,” California Tree Fruit Agreement Research Report 2002 .
Bland, Roger G. 2003. The Orthoptera of Michigan – Biology, Keys, and Descriptions of Grasshoppers, Katydids, and Crickets. East Lansing: Michigan State University Extension, Extension Bulletin E-2815. 220 pp.
Elliott, Lang and Wil Hershberger. 2007. The Songs of Insects. Boston: Houghton Mifflin Co. 228 pp (and a CD).
Headrick, David. 2000. “Fork-tailed Katydid Studies,” Citrus Research Board 2000 Annual Report.
Helfer, Jacques R. 1972. How to Know the Grasshoppers, Cockroaches, and Their Allies (Second Ed.). Dubuque, IA: Wm. C. Brown Company Publishers. 359 pp.

OrThoptera Thursday: California Angle-wing Katydid

In previous weeks I have written about the Greater Angle-wing Katydid and the Lesser Angle-wing Katydid, but there are four other species in the U.S. One of these, Microcentrum californicum, is found commonly in Arizona, and the length of California west of the Sierras.

The California Angle-wing Katydid is the smallest member of its genus, adults ranging from 41-52 millimeters. Note that the male has a brown stridulation area (its “shoulders”) like the Lesser Angle-wing, but its geographic range leaves no room for confusion.

The specimen shown here was attracted to a blacklight set up in Peppersauce Canyon in the Catalina Mountains of Pima County, Arizona on September 2, 2011. There was also a female Greater Angle-wing found in the same location on the same night.

The remaining Microcentrum species include M. louisianum, the Louisiania Angle-wing, found from Louisiana and Mississippi north through parts of Arkansas and Tennessee to the bootheel of Missouri. Microcentrum minus, the Texas Angle-wing, is found only in extreme south Texas; and the Southwestern Angle-wing, M. latifrons, is recorded from the Big Bend area of Texas and the southeast corner of Arizona.

>Sources: 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.
Eades, David C., Daniel Otte, Maria Marta Cigliano, and Holger Braun. 2013. Orthoptera Species File Online. Version 5.0/5.0
Walker, Thomas J. and Thomas E. Moore. 2013. Singing Insects of North America. University of Florida.

OrThoptera Thursday: Lesser Angle-wing Katydid

Last week I wrote about the Greater Angle-wing Katydid, a common species over much of the U.S. While reviewing images for that post, I discovered I also had images of its cousin, the Lesser Angle-wing Katydid, Microcentrum retinerve, from the same location in south-central Ohio.

The Lesser Angle-wing, as its name suggests, is a smaller animal, adults ranging from 44-53 millimeters in length compared to the 52-63 millimeter Greater Angle-wing. Males of Microcentrum retinerve have the stridulatory area consistently brown in color, a sharp contrast to the bright green of the rest of the insect. I also find that Lesser Angle-wing Katydids have the veins of the front wing more explicitly defined than in the Greater Angle-wing, making the creature even more convincing as a leaf mimic. This rougher texture is not always a defining character, but it helps.

The key character in separating these two species of Microcentrum would naturally be the most difficult to capture from images of wild, living specimens. The front edge of the pronotum (top of thorax) is smooth and straight in M. retinerve. This front margin has a very small, central tooth in M. rhombifolium.

Both species occupy the same kind of deciduous forest habitat, but the Lesser Angle-wing Katydid has a more restricted range. It occurs from Long Island and New Jersey south to northern Florida and west to Missouri and extreme east Texas and Oklahoma.

Locating a singing male can be highly frustrating, as the interval between songs is even longer than in the Greater Angle-wing; and they don’t have a “courtship song” of repeated tics. Each call is a rapid series of 3-5 pulses, too fast to count (but revealed visually in sonagrams), repeated about once per second for a short period.

Look for the adults at the tips of branches on trees at night. It is actually easier to see them in a flashlight beam than during the day because they are more active, and stand out vertically against the otherwise horizontal plane of foliage. Moving katydids are always easier to spot than stationary ones.

The Lesser Angle-wing Katydid will also fly to lights at night, which is how I obtained these few images. I am still not absolutely certain that the female is not actually a Greater Angle-wing specimen. It was climbing high on the wall and windows of a building and I could not gauge its size accurately, let alone note whether there was a tooth on the front edge of the pronotum.

Adults are most commonly encountered between late July and mid-October, but depending on latitude they may reach maturity as early as May. Other facets of behavior and life cycle are essentially identical to those of the Greater Angle-wing Katydid.

Sources: 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.
Elliott, Lang and Wil Hershberger. 2007. The Songs of Insects. Boston: Houghton Mifflin Company. 228 pp.

OrThoptera Thursday: Greater Angle-wing Katydid

One of the joys of summer nights in North America, at least east of the Rocky Mountains, is the songs of katydids. Among the more abundant and widespread of our many native species is the Greater Angle-wing Katydid, Microcentrum rhombifolium.

This is a very large insect, adults reaching 52-63 millimeters from head to folded wingtip. Females in particular are also very heavy. Let one crawl across your hand and you will feel how weighty she is. Both genders are uniformly green throughout, somewhat mottled on the legs and face. This species is among the most “leaf-like” of our katydids and is found mostly in deciduous trees.

The Greater Angle-wing ranges from Pennsylvania and New Jersey south to Florida, west to southeast Minnesota, Iowa, southeast Nebraska, Kansas, and Texas. It also wraps around the southern tip of the Rockies and Sierras, north to San Francisco Bay and throughout Arizona and much of Utah.

Adult males of this species produce two kinds of songs. The first is a “calling song” that consists of a loud “lisp” repeated an average of every two to four seconds. Producing an intermittent song like this probably prevents predators from easily locating the insect. I know it has frustrated me on a number of occasions and I have better than average hearing. Once a female is attracted, the male switches to a “courtship song” that is a series of “ticks.” The female is capable of answering this call, though she does not have the well-defined sound-producing structures the male has. The male eventually moves to find the female via this “conversation.”

Contrary to popular culture, katydids do not generate their song by rubbing their legs over their wings. The front wings of the male are modified at the “shoulders” to include a file on one wing and a scraper on the other. The file is composed of a row of peg-like teeth over which the scraper is stroked rapidly. This method of sound-production is termed “stridulation,” and the part of the wing modified is called the “stridulatory area.” Both genders hear the songs through slit-like openings on the front legs.

Once male and female are together, mating may take place. This involves the transfer of a sperm packet known as a spermatophore, produced by the male. The spermatophore is a fairly substantial ball of gelatinous protein surrounding the sperm sac itself. Once the pair disengages, the female will eat the protein mass while the sperm enter her oviduct.

The first time I witnessed mating in katydids, I thought something horrible had happened to the female, that her internal organs were oozing out of her body! The edible gift provided by the male may help foster the development of her eggs, and/or encourage her to rebuff subsequent suitors, thereby insuring it is his DNA that is carried through to the next generation.

One additional, odd note. I observed a trio of Greater Angle-wing Katydids in south-central Ohio in August of 2011 that puzzled me. One of the two females appeared to be licking the back of the male’s abdomen (see image above). I am aware that male tree crickets produce glandular secretions from the thorax near the base of their wings, but I am not familiar with an analogous situation in katydids. However, I did find other references to this behavior (Fulton, 1933; Gwynne, 2001), likewise without explanation.

Mated females deposit their eggs single-file along a twig or the edge of a leaf, each ovum overlapping the last like shingles on a roof. The eggs are vulnerable to parasites, chiefly tiny wasps in the family Eupelmidae.

The nymphs that hatch feed generally on foliage, and molt four times before reaching adulthood. While it is difficult to identify most katydids in the nymphal stage, the robust body shape, relatively short hind legs, and mottled green appearance of Microcentrum nymphs helps them to be easily separated from other North American katydid genera.

Both large nymphs and adults can be preyed upon by a number of other animals, and especially by sphecid wasps like the Great Black Wasp. Adults can fly when pressed to do so, but generally creep about slowly so as not to draw attention to themselves in the first place.

Look for the Greater Angle-wing Katydid along forest edges, in gardens and yards, even in lone trees in open fields. They are also attracted to lights at night, though not in great numbers. The best way to find them is at night, with your ears and a good flashlight. Good luck.

Sources: 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.
Elliott, Lang and Wil Hershberger. 2007. The Songs of Insects. Boston: Houghton Mifflin Company. 228 pp.
Fulton, B.B. 1933. “Stridulating Organs of Female Tettigoniidae (Orthoptera),” Entomol. News 44: 270-275
Gwynne, Darryl T. 2001. Katydids and Bush-Crickets: Reproductive Behavior and Evolution of the Tettigoniidae. Ithaca: Comstock Publishing Associates (Cornell University Press). 317 pp.