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Thursday, July 21, 2005
A BUG'S WORLD
Birds of no feather
By MARK BRAZIL
It's a strange fact but true, that if you hike regularly in the Japanese mountains, you'll see some amazing sights -- and I don't mean just magnificent scenery.
Up there, you'll find folk hiking without water bottles, peak-baggers wearing training shoes, even ladies in dress shoes emerging from gondolas and ropeways.
More amazing than these, though, are the springtime clusters of bugs.
Something most odd occurs atop mountains in spring and early summer -- a veritable congregation of insects of dozens of different species all at the summit. I can't imagine that they are smitten by the same bug (excuse the pun) as I am, and want to reach the peak. But something surely causes them to gather in swarms over summit cairns and signs.
On some peaks, I've encountered so much insect life (shield bugs, flies, beetles and, most attractive of all, ladybirds) that sitting there to rest was impossible. They weren't biting, they just crawled into my ears, my eyes, my shirt and my backpack.
Worldwide, there are more than 5,200 species of ladybirds (or "ladybugs" as they are known in the United States), and approximately 180 species of these attractive insects live in Japan. To put that into perspective, the richness of Japan's biodiversity again becomes apparent when you realize that the entire British Isles have only 41 species.
Ladybirds are among the most familiar and best loved of the commonly identified insects, being generally brightly colored and symbols of good in many myths and legends. Their strange name is derived from Christian symbolism, and relates to the common European species, the seven-spot ladybird or Coccinella 7-punctata. Originally, they were called Our Lady's Birds, referring to Our Lady, the Virgin Mary, with the red of the ladybird's elytra (wing cases) representing her cloak, and the seven black spots on the red elytra identified with her seven joys and seven sorrows.
By and large, ladybirds are small, ranging in size from just 0.3 mm to 10 mm long. They appear to be well protected from attack, with a retractable head and domed elytra meeting all the way down the middle of their backs and completely covering the soft abdomen. Their legs are short and retractable under the body, so they appear rather like rounded, colorful limpets.
As a final line of defense, if disturbed to excess, ladybirds can exude unpleasant oils from the joints in their legs -- which is perhaps one reason you don't see many creatures eating them.
Anyone raised in an English-speaking part of the world is likely to have grown up knowing the children's rhyme:
"Ladybird, ladybird, fly away home, Your house is on fire and your children are gone, All except one and that's little Ann, For she crept under the frying pan.''
This ditty, varying in minor detail from country to country, is supposed to have been in circulation since at least the 19th century, and it demonstrates a positive image that few other insects species -- save perhaps butterflies -- have achieved in the popular mind.
Some species of ladybirds are vegetarian, some feed on fungi, but most are carnivorous with a predilection for aphids and other aphidlike insects. Hence gardeners, especially those with glasshouses, have a particularly positive attitude toward them. Anywhere with aphids, such as young leaf- and flower-growth, is a good place to look for ladybirds -- so why they should occur so commonly atop mountains is hard to imagine.
Our common ladybirds all share a similar life cycle. The adults retreat into dry, sheltered sites, overwintering there often in large groups. They then emerge in spring and begin to breed, typically in May. But breeding is weather- and food-dependent, and egg-laying may continue into July, with each female laying as many as 1,000 eggs in some species.
The eggs are typically laid near a food source, so there is plenty nearby for the larvae to eat once they hatch (after about four days). The larvae bear little resemblance to the adults, and must molt three times to accommodate their growing bulk. They are known to eat more than 300 aphids before they pupate, so no wonder gardeners like them.
Once at an appropriate size, a larva will attach itself to a plant, produce a pupal skin and then, inside this miraculous case, undergo the morphological change known as metamorphosis (butterflies and moths do the same). About a week later, the pupal skin splits down the back, which allows the adult ladybird to emerge, and expand its new wings.
However, newly emerged ladybirds are pale shadows of their future selves. It takes them several hours, or even days, for their colors to brighten, but once fully winged, and fully colored they have several weeks ahead of them during which to feed and seek out their own overwintering site.
Most ladybirds have just one generation each year. It's a simple life cycle, but try as I might I have found no reference to the part where they all fly off to party on the mountain tops!
The adult stage is the longest, in some species lasting for up to two or even three years. Mating typically takes place in the spring after their first overwintering, and that is what this pair were engaged in atop Tarumae-san in western Hokkaido.
I am no advocate of a species having to have a useful purpose for us humans to grant them living space on Earth, but if one person I met who wanted all bugs eliminated should ever have their way, then surely they should allow three types at least to survive: butterflies, because they are downright beautiful; bees and their allies because they are vital pollinators of so many plant species, including many of our crops; and ladybirds, because they help regulate populations of other insects that might otherwise assume pest proportions.
In fact, ladybirds have even been introduced as biological control agents specifically to control aphids on a wide range of crops, including pecan trees, pine trees, ornamental shrubs, cotton, wheat, tobacco and roses -- and in North America, introduced Japanese ladybirds are being used in the battle against the accidentally introduced woolly adelgid, a small, sap-sucking Asian aphid accidentally introduced there in the 1920s, and which has been killing hemlock trees along the East Coast.
If you live in an older property with gaps around your windows, you may find ladybirds looking to your home as a suitable overwintering site. However, if this is not your idea of fun, try caulking gaps with a silicone sealant so that they can't enter.
Apple slices bait
If you are still hosting more ladybirds than you can cope with, use fresh apple slices as bait to attract them down from inaccessible corners or from ceilings and high walls. Then, using a dustpan and brush or a small vacuum cleaner, you can scoop them up and release them outside. It's not a good idea to squash them or kill them (after all they are widely beneficial), because when stressed they release a rather noxious smell and a harmless, but staining, orange fluid. Instead, take them outside and gently shake them into shelter somewhere, under a bush or tree, especially if it has flaking bark they might crawl under.
If you are a gardener, however, you may want to gather them up into a container and keep them in your refrigerator. The low temperature will send them into the insect equivalent of hibernation, and in spring you can release them to give you a hand in controlling insect pests.
If there are any entomologists out there with theories to explain why ladybirds might gather on mountaintops do please drop me a line, I'd be very interested to hear from you.
Mark Brazil welcomes readers' comments or questions at firstname.lastname@example.org