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.

Why I do not endorse entomophagy

It has lately become quite fashionable among entomologists to promote entomophagy, the practice of human consumption of insects as food. This is nothing new in Asia, and among many populations in the rural tropics, but is a novel concept among Westernized cultures. I personally know several entomologists who are at the forefront of the “bug chef” phenomenon. They are genuinely nice people, but I am not on board with the idea for a variety of reasons:

1. Fear Factor. Do you remember this television show from NBC? Eating insects, or spiders or other arachnids, was a grotesque challenge to contestants on this “reality” program. Throughout the developed world, eating insects is seen as something starving prisoners do, or people lost in the wilderness without other recourse. It is a punishment or last resort, not a decision one makes when they have other choices. There is good reason for that. Many insects taste horrible, or are downright poisonous if ingested. Mushrooms are a good comparison, except I think they actually taste just fine. There is no question that those pushing bug-eating have an uphill climb in overcoming the “yuck factor.”

2. Nutritional Value. Insects are basically fat and a little protein encased in chitin (the exoskeleton). Proponents of entomophagy will claim there is more to it than that, but I am boiling it down (microwaving it, whatever) to the most simplistic terms. I will not argue that as a supplement to a largely vegetarian diet, eating insects has merit. Still, the chitin, while perhaps pleasingly crunchy, is most reminiscent of those translucent yellow flakes from popcorn that you are still trying to get out from between your teeth days or weeks later. I say this as someone who has personally tried fried mealworms and other “delicacies.”

3. The utilitarian view. What I find truly objectionable about the promotion of entomophagy is the idea that insects must have some anthropocentric, utilitarian use to be of any value. They must also be dead to have value. The living insect is by far more fascinating and important than a dead one with a toothpick through it. Insects pollinate wildflowers and crops. Insects quickly consume dead and decaying flora and fauna before the corpses can breed horrible disease-causing bacteria. Insects are consumed by other animals that we find far more tasty, like fish and poultry for example. Ok, I’m kidding a little bit, but insects are an incredibly important part of the natural food chain.

Insects also produce goods and services that are of great use to humanity. Would we suddenly see the honeybee as food itself, instead of as a maker of food? I know a professor who has had contracts with the Department of Defense to study the employment of insects as detectors of explosives and other substances used by terrorists. This kind of work actually enhances our admiration of insects and their superior chemo-tactile senses. Other scientists study insects to find ways of improving the aerodynamics and mechanics of flying aircraft; and as models of locomotion for robotics. Insects are not products, but that is the only context in which some people think they have value.

I will always hold my fellow entomology colleagues in high esteem, but I do wish they would step off the entomophagy bandwagon for a spell and talk to the public more about the intrinsic value of beetles, wasps, bugs, and flies. Meanwhile, I suspect the comments on this post to offer plenty more “food for thought.”