At Hilton Pond Center, here's what we like about Japanese Beetles:

• Their bright metallic colors.

Here's what we don't like:

• Everything else.

Although we try not to make value judgments about nature, we have few good things to say about Japanese Beetles (Popillia japonica). The western world easily could have gone without the introduction of these prolific foliage-feeders that were brought accidentally to New Jersey from the Orient in 1916. With none of their natural predators or diseases around to keep them in check, Japanese Beetles spread rapidly and today are entrenched firmly in the eastern third of the U.S. Adult beetles and their larvae occasionally show up in commercial shipments to California, but the pest fortunately hasn't gotten a good claw hold on the West Coast.

The Japanese Beetle (above) is easily identified by its dark metallic green head and thorax, bronze wing covers, and a row of bright white spots down each side of its abdomen. The spindly hind legs are especially long and often angle out from the body while the beetle is feeding.

Adult Japanese Beetles are almost exclusively herbivores, dining in the U.S. on foliage of as many as 400 species of broad-leaved plants. They also nibble on fruit, and perhaps their most irritating habit at Hilton Pond Center is to hide within a succulent cluster of ripe Blackberries. There's nothing worse than popping a handful of these delectable wild fruits into one's mouth and having to spit them all out because a bitter beetle hitched a ride. (Adding injury to insult, it's also no fun at all when the pesky little insect scratches around on the back of one's tongue!)

While feeding, Japanese Beetles release an "assembly" pheromone that attracts others of their species, and the whole congregation joins in to chow down on whatever food source is at hand. Rather than eating an entire leaf, however, adult beetles consume the blade and not the veins, as shown in by Blackberry leaflets (above right). This skeletonized foliage usually dies fairly quickly, depriving the host plant of its photosynthetic capabilities and forcing the beetles to move on toward greener pastures. (By the way, it's often hard to get a photo of Japanese Beetles feeding. When a predator--or photographer--approaches, the beetles typically freeze and then drop toward the ground, sometimes taking flight and usually evading the camera.)

Along with their "assembly" pheromones, well-fed female beetles also yield a scent that drives their male counterparts into a frenzy, creating an orgiastic scene with several potential mates scrambling for each female's approval. In mid-summer, the fertilized female burrows a few inches into the soil and lays a half dozen eggs. Then she re-surfaces, feeds, and mates again, repeating the cycle every several days until perhaps 50 eggs are produced and deposited in the substrate. By the end of July, nearly all Japanese Beetle adults at Hilton Pond Center are dead--no doubt worn out from all that eating and mating--but their progeny are safely underground in the egg stage.

In hot weather, Japanese Beetle eggs take only about ten days to hatch, after which the grubs (left) make their living dining on subterranean roots--especially those of turf grasses. (Hmmm. Here's a second thing we might like about Japanese beetles: their larvae are a plague upon unnatural grassy monocultures that most people call "lawns.") Japanese Beetle larvae spend the fall, winter, and following spring tunneling around, eating more roots, aerating the soil, and making a regular mess of manicured yards. By late May, the grub forms a pupa (photo at lower right courtesy USDA), and a new crop of adults emerges a month or so later to start the cycle anew.

Hmmm, again. We just thought of a third aspect of Japanese Beetles that we like: at Hilton Pond Center the adults dine ravenously on Multiflora Rose (Rosa multiflora), another scourge from Japan that competes far too effectively against native plants.

So maybe Japanese Beetles aren't so bad after all. They're pleasing to the eye, their grubs gobble up lawns, and the adults eat invasive plants. Now if we could just keep those Japanese Beetles out of our Blackberry patch . . .

The following species were banded this week (29-31 July):

Ruby-throated Hummingbird--4*
White-eyed Vireo--1*
Chipping Sparrow--1
Black-and-white Warbler--1*
Red-eyed Vireo--4*
Northern Cardinal--9*
Eastern Towhee--2*
Wood Thrush--3*
Carolina Wren--1*
Eastern Tufted Titmouse--1*
House Finch--8*
American Robin--1*

* = Includes at least one Recent Fledgling

All photos & text © Hilton Pond Center

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