Moths in winter
Dec.21,2001. M.Sekine
Colorful and graceful butterflies are among the most widely appreciated
insects. While their relatives the moths fare poorly in popularity contests,
butterflies may win out handily in popularity but, in terms of evolutionary
success, it is the moths that come out squarely on top. The number of species
of moths is ten or more times those of the butterfly. Actually, about 240
species of butterflies inhabit Japan, while the number of species of moths
is at least 3,000, and probably much more.
Some 20 species of fuyu-shaku moths (literally, "winter-measuring-worm
moths") have been recorded throughout Japan. These are the only moths
known to appear in winter. Fuyu-shaku moths emerge only once a year,
in winter, from their cocoons in the ground. Curiously enough, they have
no mouth-parts. Therefore, fuyu-shaku moths don't take in food in
adult stage. The most common species is kurosuji-fuyu-edashaku (literally,
"black-striped-winter-cankerworm moth"), belonging to the family
Geometridae. Their scientific name is Erannis obliquaria.
It is fascinating to see a flight of 30-odd male adult moths flit over
fallen leaves in coppices in the daytime from late autumn through early
winter. They search for the females. The female adults, however, are wingless.
Perhaps, they adapt themselves to severe winters by losing their wings and
by not eating at all.
As insects go, they are the stars of the winter. I'm deeply impressed
by their intriguing physical and behavioral characteristics as described
above.
Just one more thing, the spider, Labulla contortipes, belonging
to the family Linyphiidae also matures in winter. Perhaps, this spider emits
components of the moth-prey species' sex pheromones, imitating a chemical,
to lure the male fuyu-shaku moths. Nature is becoming full of surprise.
