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.

Courting Robber Flies

It must be spring. Love is in the air, on twigs, on the ground....at least if you are watching insects. They are courting and mating everywhere. My last couple of outings afield on the plains here in eastern Colorado have given me the opportunity to witness some insect romance up close; and I remembered to use the video function on my camera, too.

Male Ablautus(?) robber fly with leafhopper prey

One particularly abundant insect in early spring is a small robber fly, family Asilidae, possibly in the genus Ablautus. Adults of this dipteran measure only about 6-7 millimeters, and they are sand-colored, so rather difficult to see. They prey on insects smaller than they are. The one in the image above has killed a leafhopper.

I discovered that the males are slightly smaller and more slender than females, with bright white hairs on their faces. Females have gold or ochre-colored hairs on their faces.

Female Ablautus(?) robber fly

Males are very energetic, and once engaged in courting a female, they are not easily frightened away. So, once I discerned there was a pair of the flies on the ground in front of me, I stopped and watched. This is the amazing result. The male alights near the stationary female, then flies and alights again, sometimes sidling into a different position. Eventually, he waves his front legs in front of her and rocks up and down. It is quite a display.

This next video is of a different pair of flies, perhaps a little farther along in the process, because it has an, uh...."happy ending." The male is the one with the smile on his face.

Many flies have elaborate courtship rituals, but asilids (robber flies) have some of the fanciest. I was lucky enough to also capture video of the aerial display of Heteropogon macerinus in Ohio a couple of years ago.

Robber fly "wedding photo"

I urge you to find your own examples of "bug love," and document them with your camera, even your smartphone. There are plenty of places to share the results online. Maybe your video will even go viral on YouTube. In any event, we stand to learn a good deal more about insect behavior through the efforts of curious citizen scientists.

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.

Bugs in Love

Happy Valentine’s Day! No matter whether you, or any other person, loves insects, there is no question that they love each other. There are few things arthropods are better at than procreating, so on this day of love why not celebrate their courtship and mating?

True bugs like the Eastern Boxelder Bugs above, often mate “tail-to-tail.” It is one way to differentiate them from beetles, which usually mate stacked up, the male on top. Take the two tiger beetles below, for example.

The video below shows a pair of blister beetles (genus Epicauta) that I found here in Colorado Springs. The male is in the rear, rocking back and forth and literally tickling the fancy of the object of his affection with his antennae. You’ll have to add your own sound track, maybe Barry White or Marvin Gaye. Ooooooh....yeah.

Butterflies, like most insects, rely heavily on pheromones to attract the opposite sex. Pheromones are species-specific volatile chemicals produced mostly by the female, but sometimes the male. The picture below depicts a pair of Heliconius hecale in the “Butterfly Magic” exhibit at Tucson Botanical Gardens. The female is perched on the leaf while the male hovers above.

In this case, he is wafting his own pheromones toward her. Unfortunately for him, the posture of the female is the Lepidoptera equivalent of flipping one’s middle finger. Nice try, guy. Better luck next time.

Some male insects have a “hit-and-run” mentality, literally. Male European Woolcarder Bees, Anthidium manicatum, stake out territories around resources used by the females. They will rout any other males, and any other bee species, from a patch of flowers, for example. When a female lands on a flower and tries to go about the business of harvesting pollen….BAM! The male bee forcibly accosts her, mating with her whether she wants to or not. The session ends after only a few seconds.

Among the more gymnastic of mating rituals occurs in the Odonata: the damselflies and dragonflies. It still may not be much fun for a female, as the male grasps her tightly around the neck with the claspers on the end of his abdomen. Some dragonflies even end up puncturing the eyes of their mates with the prongs and spurs on their claspers.

A compliant female will, however, bend her abdomen up to meet the base of her mate’s abdomen, as his sperm duct is located there. A pair of mating damselflies or dragonflies thus forms a “wheel,” often in the shape of a heart. What a fitting image for Valentine’s Day.

King of the Dung Heap

Some of the most beautiful insects in the world are found under the most disgusting of circumstances. Take, for example, the subject of this week’s “Fly Day Friday.” The Golden Dung Fly, Scathophaga stercoraria, is a common species, especially in early spring and autumn. Unfortunately, it is most abundant around cow and horse manure.

The male fly, about 7-9 millimeters in length, is covered in long, bright yellow or golden hair. The insect positively glows when the sunlight strikes its body at just the right angle. Females are often smaller, and rather dull brown or gray. Males are quick to colonize a fresh heap of dung, many individuals descending on the meadow muffin. The flies are predatory on other, smaller flies that try and compete with their monopoly on the dung.

Females covet fresh scat as food for their offspring, but they first have to endure a mob of bachelors attempting to mate with them. Larger males are usually more successful at copulation than smaller individuals, but in the frenzy they sometimes mistake others of the same gender for females. Males repel such unwanted advances by pushing themselves up on their front and hind legs and kicking the would-be suitor off their back with their middle legs.

Even after mating a female is usually accosted by other males trying to “get in the last word,” so to speak. The kicker is that the female has three, sometimes four, spermathecae, internal storage chambers for sperm within her abdomen. So, not only is there external competition between male flies, but competition among their sperm, inside the female. Still, the last male to mate with a given female will fertilize about 80% of her eggs.

He often guards the female while she deposits her eggs. According to one study it takes her an average of forty-five minutes to complete oviposition. Manure that dries out, forming a crust, is nearly impossible for the flies to penetrate when laying their eggs, so there is a premium on freshness.

There is a surprisingly voluminous amount of information about the mating habits of this species, which any Google or Google Scholar search will reveal. There are even some online videos, and not all of them R-rated. The flies are easy to observe in the field, and easy to propagate in the laboratory, so they make good subjects for students and scientists, no doubt.

When not engaged in sexual behavior, or searching for poop, dung flies can be found peacefully sipping nectar from flowers, especially in early spring. I often see them on willow catkins, where they will also prey on smaller flies (see photo above). There are several generations of these insects throughout the warmer months, but they seem to be most conspicuous in spring and fall.

The Golden Dung Fly has a nearly worldwide distribution, and is not surprisingly most abundant in habitats frequented by livestock and large, wild mammals. So, forest edges, meadows, fields, farms, and ranches are good places to find them in great numbers. Not that you would want to go out looking for feces or anything….

Sources: Preston-Mafham, Rod and Ken. 1993. The Encyclopedia of Land Invertebrate Behaviour. Cambridge, Massachusetts: The MIT Press. 320 pp.
Ward, Paul I. 2000. “Cryptic Female Choice in the Yellow Dung Fly Scathophaga stercoraria,” Evolution 54(5): 1680-1686.

Wasp Wednesday: Wasps in Love

It seems the theme lately has been insect sex. Seriously, I don’t think I’ve ever seen and photographed so many f*ing “bugs” (literally!) as I have in the past week or two. Wasps have been no exception. It is one of those behaviors for which they tend to sit still for a change. It is also a situation in which you can finally tell the subtle differences between the genders (or not so subtle differences in some cases).

Take the example of the pair of Ammophila thread-waisted wasps shown above. The male is the one on top. The tip of his abdomen is rather blunt, and that he is deploying his, um, “hardware.” The female doesn’t seem to like this very much, though. Notice how her abdomen tapers to a point.

One may logically ask how can mating take place when a female wasp has a stinger. Wouldn’t that hurt the male? How can he get his sperm into such a small, sharp opening? Well, the stinger is not involved in copulation. In the evolution of wasps, the egg-laying organ (ovipositor) has in some cases become modified into a retractable stinger that is now used to paralyze prey, and as a weapon of last resort in self-defense. The female’s sex organs are located near the same opening from which the stinger is thrust, but again, the stinger does not participate in mating activities.

While the sexes are very similar in most kinds of wasps, this is not always the case. Above we have a pair of pollen wasps, Pseudomasaris vespoides, the male attempting to court a female that has her head stuck inside a Penstemon flower. Many male wasps are, shall we say….opportunistic in this way. To his credit, he is petting his potential mate, tapping his “chin” on her back. I wish I had video to demonstrate that, but I don’t. The male is larger than the female, with various hooks and other external anatomical features on his abdomen that help him latch onto his mate. Pseudomasaris males also have much longer antennae than the females, terminating in segments that form a club. She has clubbed antennae, too, just much shorter.

Male wasps may have other body parts modified as well. Males of crabronid wasps in the genus Astata have enormous eyes that meet at the top of their heads: all the better to see passing females as he sits atop an elevated perch. He will also chase off competing males.

Above is a male wasp in the genus Crabro. He has the tibial segment of his front leg modified into a broad shield. Scientists speculate that these plates function in displaying to females and other males, and/or as stimulation to the female during courtship. The shields glisten in the sun, reflecting light brightly and perhaps disclosing the location of the perched male to passing females and competing males. During courtship, the male perches atop the female and covers her eyes with his shields. The shields are translucent and create patterns of light perceived by the female (Low and Wcislo, 1992).

There is much competition among males for available females. This was made graphically clear to me earlier this week when I received an image from someone via AllExperts.com, asking me “what behavior is going on here?” The picture showed three male Black and Yellow Mud Daubers, Sceliphron caementarium, stacked on top of a single female. Well, two of the males were stacked on each other, actually.

Females of Eremnophila aureonotata, a thread-waisted wasp, don’t let mating keep them from other activities. The pair shown below is resting, but “engaged” pairs can often be seen flitting from flower to flower just like single wasps. This species is common throughout the eastern U.S. and adjacent southern Canada, so keep a lookout for tandem couples.

In the interest of maintaining my current followers, and in the hopes of recruiting still more, I shall refrain from any comparisons between wasps and Homo sapiens when it comes to sex. I encourage voyeuristic behavior only when it comes to watching insects and arachnids, thank you.

Sources: Bohart, R. M. and A. S. Menke. 1976. Sphecid Wasps of the World: A Generic Revision. Berkeley: University of California Press. 695 pp.
Low, Bobbi S. and William T. Wcislo. 1992. “Male Foretibial Plates and Mating in Crabro cribellifer (Packard) (Hymenoptera: Sphecidae) With a Survey of Expanded Male Forelegs in Apoidea,” Ann. Entomol. Soc. Am. 85(2): 219-223.

Butterfly Love

Spring is in the air here in Tucson, Arizona, and apparently the thoughts of butterflies are turning to love. I wrote the following for the Valentine’s Day issue of the volunteer newsletter at the Tucson Botanical Gardens, but cruising the grounds this past week I saw plenty of native butterflies in “action,” so to speak, like this pair of Giant Swallowtails outside our administration building.

Visitors to Butterfly Magic will never fail to notice when two butterflies are conjoined, and will ask you what is going on with that. Well, ok, so the butterflies themselves are not shy when it comes to courtship and sex. They have a limited amount of time to find acceptable mates and produce the next generation.

Among the more dazzling behaviors butterflies engage in is courtship. There are great differences in courtship behavior from family to family, and even species to species, but you can easily recognize certain postures and flight styles as romance-intended. Females may advertise their availability by perching with wings open and abdomen slightly raised. She may also “call” males by releasing a special chemical called a pheromone. Males detect the wind-wafted scent with their antennae and then quickly recognize her visually. Male giant silkmoths like the African Moon Moth and the Forbes Moth can home in on a female from up to a mile away (maybe even longer) by following her pheromone trail.

Male butterflies of many species have pheromones, too, designed to communicate individual fitness to a potential mate. Once he locates a female the male must convince her he is a worthy investment. He may do this by following her in flight until she lands, then hovering over her and showering her with his own “cologne” emitted from special scent patches on his wings, or from “hair pencils,” glands that he extrudes from the rear of his abdomen. Males of some Heliconiinae (longwings) go a step further and sprinkle an anti-aphrodisiac once mating has occurred. This discourages other males from usurping his genetic investment in that particular female’s offspring.

Should the female be disinterested in a suitor, she changes her posture, pointing her abdomen nearly straight up and essentially “mooning” the male.

The pursuit and hovering displays are characteristic of the male Priamus Birdwings and the Heliconius longwings. Morphos are less elegant. Males will land next to perched females and aggressively “nudge” them into compliance. Watch as a male bends his abdomen forward in an attempt to copulate.

Compatible males and females may eventually couple, tail-to-tail, facing in opposite directions. Males might even hang limply from the female as she remains perched. Occasionally the pair will even take flight, one of them carrying the other. Butterflies can remain coupled for as little as a few minutes to several hours. We had one pair of Priamus Birdwings (shown above) engaged for so long that the male actually perished while still connected to the female. While lengthy mating leaves both butterflies vulnerable to predation, it also prevents other males from mating with a given female, increasing the odds that the male will see some of his genes represented in the next generation produced by that female. Nature is full of such trade-offs.

Butterflies have the same sex organs as other animals, but they go by different names. The male penis is called an aedeagus (ee-dee-AY-gus). The shape and configuration of the aedeagus varies from species to species, largely preventing hybridization between different species. He also has claspers, the external genitalia that hold the couple together during sex. The female has a vagina (the “bursa copulatrix”), but also has a “receptaculum seminis” or “spermatheca,” a sac that stores sperm. Her eggs will not be fertilized until she lays them.

Whew! I managed to get through all that without even talking about contraception and the Butterfly Vatican.

A pair of Texan Crescents is shown above.