Common Name: Japanese Beetle – Unlike many animals and plants broadly referred to as Asian in origin, there is no doubt that this beetle was inadvertently introduced from Japan to the United States and spread, becoming an agricultural Juggernaut.
Scientific Name: Popillia japonica – The genus is based on a well established Roman surname. Marcus Popillius Laenas was consul, one of the Roman Republic’s two top magistrates, noted for his defeat of the Gauls in 359 BCE. He was the first of a long line of distinguished Roman leaders named Popillius. There is no known connection between any of these descendants and beetles. The species name establishes geographic origin in Japan.
Potpourri: The Japanese Beetle is a case study in the invasive behavior of an alien species in the life and times of the twentieth century. Its clandestine point of entry in August 1916 was New Jersey in the form of beetle larvae ensconced in iris rhizomes imported from Japan as horticultural garden center offerings. [1] Spreading at a rate of about 10 miles per year, the shiny green and brown scourge has ravaged planthood in the eastern half of North America for over a century. The root munching grubs eat voraciously through turf all summer long, despoiling large swaths of lawns, or, if used to hit balls and then go find them, golf courses, only to become adults after wintering over six inches deep. What follows in spring after pupation is a two month feeding and mating frenzy culminating in the turf deposition of some 50 eggs per female to sow the seeds for Malthusian beetle populations. With an annual agricultural loss cost estimated at half a billion dollars, they have spawned a whole industry of eradication and control.
Beetles are by some measures the most successful of earth’s inhabitants. With more than 300,000 species worldwide, they comprise about one fourth of all described animals―a thousand beetles for every primate. This is in part due to an “intelligent” design. The Order Coleoptera to which they are assigned is literally Greek for ‘sheath wings,’ describing their key taxonomic anatomical similarity. The hardened, chitinous front wings encase the more delicate rear wings with an armored barrier similar in form and function to a box turtle’s carapace, protecting the beetle from many an unwelcome intruder. These encapsulating forewings, which are called elytra, the plural for elytron which also means ‘sheath’ in Greek, unfold with an elaborate linkage of struts and elbows to release the diaphanous rear wings for flight. The beetle, a six-legged biological version of the bipedal transformer toy, thus converts from a stolid, tank-like ground vehicle into a clumsy but functional airfoil to find food, to find a mate, to escape emergent threats, or simply to gad about on summer days. [2] The aphorism that the Creator must have had an inordinate fondness for beetles because he made so many of them is frequently attributed to Charles Darwin. The more likely source is British entomologist J.B.S. Haldane who wrote that “the Creator would appear as endowed with a passion for stars, on the one hand, and for beetles on the other for the simple reason that there are nearly 300,000 species of beetle known, and perhaps more …” [3] The versatility and resilience of beetles is notable, divine or otherwise.
Japanese beetles are in the family Scarabaeidae, usually referred to as simply scarabs, which comprise one tenth of all beetle species (a mere one hundred per primate). The historical importance of the scarabs is evident in nomenclature. Scarabaeus is Latin for beetle, which probably came from the Greek karabos, meaning horned beetle, with good reason. According to the dated but enduring Linnaean taxonomy, scarabs are distinguished in having the last 3 to 7 sections of their 10 segmented antennae formed into a lamellate or plate-like club; lamellicorn beetle is an alternative name. The notoriety of horn-beetle scarabs is due in part to their relatively large size, and, in many cases “outgrowths on head and thorax” that “produce bizarre forms.” [4] But the more surprising scarab origin story is central to Egyptian mythology. Khepri was one of the names for their Sun god (along with Ra, Atum and Horus) that is a cognomen taken directly from kheprer, the Egyptian name for the dung-beetle. Many scarabs feed on animal feces and other decaying matter as a nutritional niche. The dung beetle carries this one step further, molding the semi-solid stool into balls that can be rolled along the ground and deposited into a purpose built hole. Here the eggs are laid so that hatched larvae will be provisioned with their first feast. The Egyptian holy men interpreted the dung ball as representing the sun being pushed into the “Other World” at dusk and back over the horizon at dawn. Thus the scarab amulet, a signature Egyptian embellishment and adornment, symbolized “the renewal of life and the idea of eternal existence.” [5] The transubstantiation of the bread and wine of communion into the body and blood of the Christian deity that are then consumed in sacristy is no less outré.
While dung is not on the menu for the Japanese Beetle, just about everything else is, earning it the distinction of being considered polyphytophagous, Greek for “many plant eating.” While roses and fruit trees are its most notorious targets, the beetle smorgasbord includes at least 435 identified species from 95 families including garden and field crops, ornamental shrubs, and shade trees. The choice of one plant over another is related at least in part to scent. Research has demonstrated that the phytochemicals eugenol and geraniol are particularly attractive―the fact that roses contain both provides some empirical validation. Exacerbating the beetle invasion problem (beetlemania?) is their tendency to congregate on one plant, creating a writhing mass of coruscating green and brown. Field testing has revealed that twice as many beetles alight to join a party in progress, eschewing adjacent plants of the same species for no apparent reason. Both the quality and quantity of the meal must surely suffer as communality prevails. With a preference for plants in direct sunlight, the banquet starts at the top, stripping the foliage downward by eating between the leaf veins, leaving characteristic lacelike skeletons as remnants. In many cases, the plant is left totally defoliated and dies as a result. In one field test 2,745,600 beetles were collected from 156 peach trees … an average of 17,600 per tree. As half of that population would be female, the ensuing egg deposition in nearby fields would result in a veritable contagion of larval grubs, eating away at the roots of the ecosystem to the detriment of both field and forest. [6] The scourge of the Japanese beetle to an environment unprotected by native predators can be apocalyptic.
Evolutionary success for any animal species requires a minimum of two surviving adults to replace each gravid female. In insects, this is achieved predominantly by depositing large caches of fertilized eggs that hatch to larvae and pupate to adults mating in sufficient numbers to establish perpetuity. Japanese beetles evolved to survive predation and attrition in their native habitat, primarily the grasslands of northern Honshu and the whole of Hokkaido. In the United States they are unchecked, and their sexual drive to survive has produced exorbitant dividends. Male beetles are equipped with a penis-like aedeagus to inject cyst-encapsulated spermatozoa into the female vagina. The instinctual male mating mandate is triggered by the pheromones of emergent virgin females; they descend en masse, forming large clusters called “beetle balls.” One experiment using females in a trap collected almost three thousand males in one hour. Mating attempts persist throughout month-long adult lives. Coitus occurs primarily on leafy foliage that doubles as dining room and can last for several hours. Speaking of balls, one male was observed mating with seven different females in a single day and another was observed mating with at least two different females over five consecutive days. Females take periodic breaks from the action to dig about three inches into the soil to lay several eggs only to return to remate and repeat, ultimately laying about fifty. [7] A population bomb nonpareil.
The exploding growth of Japanese beetles was noted within two years of their initial introduction in a nurseryman’s refuse pile in Burlington County New Jersey in 1916. By 1920, 1,000 quarts of beetles were collected in one half square mile and two years later, the area had expanded to six square miles. In 1923, when the range had surpassed 700 square miles and extended into Pennsylvania, the clarion call was sounded at the national level. The USDA dispatched scientists to Japan to search for predators and began evaluating pesticides for control and remediation. [8] But it was too little too late and by 1970, the range had reached at least 150,000 square miles and extended over 14 states. Despite extensive efforts to stem the tide, it is now established in 30 states. While it was long thought that the Rocky Mountains and the Great Basin would present an impenetrable barrier to their westward migration, Japanese beetles have recently made landfall in the Pacific northwest. It is postulated that adult beetles hitched a ride on an airplane or that larvae arrived surreptitiously in the root soil of imported plants. [9] The economic costs have grown accordingly. The Japanese beetle larva is the worst turf-grass pest in the United States; control costs are estimated at $460 million annually. This estimate is not inclusive of crop damage and the devastation of ornamental shrubs like rose bushes. While this is hardly chump change, it pales in comparison to the annual costs of invasive species, which is on the order of $20 billion. The highest invasive species costs are attributed to mammals, primarily due to rodent crop damage. Plants are next due to strangling vines like Amur honeysuckle. Insects place third, led by the red imported fire ant (or RIFA) of the southwest with an annual cost of $1.5 billion. [10] The Japanese beetle has the distinction of being one of the first invaders and one of the most visible if not the most costly. It can only get worse with a warmer climate.
In an attempt to mitigate some of the economic and aesthetic damage, farmers and homeowners usually start with chemical warfare, primarily with pesticides based on permethrin and carbaryl. The former is known as one of the best deterrents to ticks when applied to clothing for hikers and soldiers, but the latter is more widely used because it is cheaper. The insect killing euphemism pesticide captures the insidious effects of chemicals when widely applied to farm fields and home gardens. The extermination of “pest” species like Japanese beetles also eliminates beneficial insects like butterflies and bees. The insect Armageddon of the last several decades is an unsettling result due in no small part to its food chain effect; many birds rely on bugs for protein. There are certainly eco-friendly alternatives based on botanicals, but they are for the most part deterrents that only last for several days. The main effect is to shunt the beetles temporarily to another location like your neighbor’s garden. A second line of defense utilizes Japanese beetle traps that emanate vapors made from a combination of virgin female pheromones and a treacly blend of fruits. The problem is that the traps are much more effective at attracting beetles (especially males) than they are at capturing them. The end result follows the law of unintended consequences: more traps, more beetles.[11]
The obvious but complicated alternative is biological control. Difficulties arise not only in the identification of the appropriate control organism but also in ensuring that the cure does not become a curse. It is a factual matter that invasive species come from somewhere where they are not invasive … held in check by their native evolved ecology. While the first step is to scour home turf for potential predator imports, an assessment of viability to the new environment is equally mandatory. Among the notable failed biological control attempts was the introduction of mongooses to Hawaii to kill crop-eating rats. The diurnal mongooses never hunted the nocturnal rats, decimating the bird population instead. In the case of beetles, the task is not as onerous since many wasps are masters of insect parasitism and, not infrequently, one species of wasps specializes in one species of beetle. The Spring Tiphiid Wasp (Tiphia vernalis) was introduced to North America in the 1920s for its known parasitism of Japanese beetles. As one of natures more insidious predators, the female wasp burrows into the soil to locate a beetle grub, paralyzes it with a sting, and lays its egg that hatches to a larva that feeds on the now immobilized carcass. While effective, the tiphiid wasps alone have failed to check the Japanese beetle onslaught and other controls have been identified. The Winsome fly (Istocheta aldrichi) was also imported from Japan as a control vector. It deposits eggs on the thorax of adult female beetles which hatch to maggots that burrow under the outer wing covers to consume the softer body parts. There are also insect eating nematodes and several types of bacteria that are employed in the never ending battle to thwart the Japanese beetle invasion. But so far, it is at best a standoff. [12]
The impracticality of eradicating an invasive species like the Japanese beetle renders damage control as the only feasible alternative. The ounce of prevention as a pound of cure method is to establish protocols to halt the human-assisted migration of beetles from an infested part of the country to new territory. Nine western states have signed on to the USDA Animal and Plant Health Inspection Service (APHIS) Plant Protection and Quarantine (PPQ) program to monitor Japanese beetle populations and stop migration. Airports are assessed for local beetle populations and aircraft are treated to minimize the chances for the spread from infested areas to the protected states. [13] While this will lower the risk, it will not eliminate it. With some irony, it has been pointed out that, for all the human chemical, control, and programmatic efforts, the Japanese beetle has outsmarted us. Therefore, the first rule of Japanese beetle control is that you can’t control Japanese beetles. It is possible to reduce the damage by using chemical sprays selectively on their favorite plants like roses and kill enough to prevent their spread to other plants, a process called trap cropping. Another possibility is to encourage limited growth of plant invasives such as multiflora rose and Japanese knotweed that Japanese beetles demonstrably prefer. But be ever mindful of who is in charge. The final rule of Japanese beetle control is that they will “seek revenge for their dead relatives.” [14]
References:
1. Milne, L. and Milne, M. National Audubon Field Guide to North American Insects and Spiders, Alfred A. Knopf, New York, 1980, pp 561-562
2. Marshall, S. Insects, Their Natural History and Diversity, Firefly Books, Buffalo, New York, 2006, pp 257-258.
3. Haldane, J.B.S. What is life? The Layman’s View of Nature, L. Drummond, London,1949, p 258.
4. Gressitt, J. “Coleoptera”, Encyclopedia Britannica, 15th edition Macropedia Volume 4 William Benton Publisher, Chicago, Illinois, pp 828-837.
5. Viaud, J. “Egyptian Mythology” New Larousse Encyclopedia of Mythology, Hamilton Publishing Group, Ltd. London, 1973, pp 9-43.
6. Fleming, W. “Biology of the Japanese Beetle” USDA Technical Bulletin Number 1449, July 1972. https://naldc.nal.usda.gov/download/CAT87201410/pdf
7. Gyeltshen, J. et al “Japanese Beetle” University of Florida. https://entnemdept.ufl.edu/creatures/orn/beetles/japanese_beetle.htm
8. “Japanese Beetle Ravages”, Reading Eagle Newspaper Article 22 July 1923 extracted from New York Herald.
9. Betts, A. “Japanese beetle count passes 20,000” Washington State Department of Agriculture Ag Briefs. 3 September 2021. https://wastatedeptag.blogspot.com/2021/09/japanese-beetle-count-passes-20000.html
10. Fantle-Lepczyk, J. et al “Economic costs of biological invasions in the United States” Science of the Total Environment, Volume 806, Part 3, 1 February 2022. https://www.sciencedirect.com/science/article/pii/S0048969721063968?via%3Dihub
11. Potter, D. et al “Japanese Beetles in the Urban Landscape” University of Kentucky College of Agriculture, Food, and Environment Entomology Department. https://entomology.ca.uky.edu/ef451
12 “Managing the Japanese Beetle: A Homeowner’s Handbook. USDA, Washington, DC https://www.aphis.usda.gov/plant_health/plant_pest_info/jb/downloads/JBhandbook.pdf
13. USDA Animal and Plant Health Inspection Service (APHIS) Japanese Beetle Handbook https://www.aphis.usda.gov/import_export/plants/manuals/domestic/downloads/japanese_beetle.pdf
14. Gillman, J. “Disney and Japanese Beetles”. Washington State University, 18 March 2010
Hiker's Notebook 