Searching for lightning bugs
With vast numbers of vanishing species around the world, what is it about fireflies that makes them so important and Ho so infatuated with them? Just like carnivorous animals such as eagles and owls, fireflies, which eat snails and shellfish, occupy a high position on the food chain. If lower links in the chain are affected, it will influence the fireflies' living conditions. Thus, these insects serve as an excellent gauge of the condition of the natural environment.
Firefly larvae feed on small mollusks. During feeding, they latch onto their slow-crawling prey with their mandibles and secrete saliva that anesthetizes them. Next, external digestion takes place: digestive juices dissolve the food into liquid form, which they consume. Their mouthparts atrophy when they become adults, from then on normally consuming only dew. About 20 days later, after reproducing, they die.
Because of this, some people think that if you set snails free in an area, soon you'll see swarms of fireflies. "Impossible!" says Ho. For the species to survive, they need more than food; they also require a setting conducive to reproduction and other activities. If the habitat isn't just right, how can one hope to see fireflies?
Light pollution is a chief offender in the disappearance of fireflies.
"Light pollution interferes with fireflies' signaling abilities," says Ho. No matter how much effort they put into flashing their lights, they can't mate if they can't see each other. As a result, fireflies are doomed to annihilation in bright, neon-lit urban areas.
The Urban Forest-Bathing Area of Zuoying, Kaohsiung, is one of the few successful examples of urban firefly restoration. After three years of painstaking habitat conditioning and efforts by the city's Bureau of Public Works to minimize urban lighting during firefly mating season, these insects have finally found a place to live in the city.
In rural areas less affected by light pollution, fireflies are met with additional problems: water resources polluted by pesticides and herbicides, as well as inappropriate management of rivers and streams.
There are two kinds of fireflies: aquatic and terrestrial. Aquatic fireflies lay their eggs on clay mounds by the water's edge, so when concrete embankments are laid by streams and drainage ditches, suitable egg-laying spots are eliminated, hampering firefly reproduction. In Taiwan, only three such species remain: Luciola ficta, Luciola hydrophila and Luciola substriata.
Clean water is a necessary condition for the survival of fireflies. "Fireflies have quite high standards for water quality. To survive, they require an oligosaprobic environment; that is, one in which the water is rich with oxygen and low in organic matter."
On top of this, fireflies are unable to survive in places sprayed with pesticides and herbicides. "Fireflies are very sensitive to pesticides," notes Ho. He once fed firefly larvae with snails that he found by the roadside, and observed that the fireflies died soon after eating. He found after dissection that the narrow anterior gut of the larvae, which derive their nutrients through external digestion, was ulcerated by the pesticides consumed by the poisoned snails.
Fireflies go through four stages of metamorphosis: egg, larva, pupa and adult. The photo on the left shows snail-eating larvae, in the middle is a pupa, and on the right are adults mating.