The nocturnal singing of coquies is beloved in Puerto Rico, especially after several years of unexplained population decline. Is there any chance that the little coquies can be returned from Hawaii?

Mario A. Loyola
Mayaguez, Puerto Rico

The Coqui Hawaiian Integration and Reeducation Project (CHIRP) is applying for an export license for coquies .—J. Raloff Your article was extremely one-sided. In fact, many people here in Hawaii love the frogs’ sound, and they may prove beneficial since they eat invasive insects. We need to develop humane environmental control methods, not cut-and-burn environmentalism, as has been proposed.

Sydney Ross Singer
Pahoa, Hawaii

This article confuses me. For years, I’ve been reading about the mysterious worldwide decline in frog populations. Also, why does caffeine kill off frogs and slugs but not insects?

Lorien Davy
Santa Barbara, Calif.
Frogs seem to be disappearing in lots of places for a variety of reasons, from habitat loss to poisoning and introduction of new predators. As for caffeine, the compound easily penetrates frogs’ and slugs’ moist skin but not insects’ hard exoskeleton.—J. Raloff You ask the question “Whose dinner are the coquies stealing?” In fact, dinner for coquies or any other carnivore in Hawaii contains mostly items among the 5,200 native insect species. The loss of insect species is an irreplaceable loss to world biodiversity.

James K. Liebherr
Ithaca, N.Y.

My wife and I find that the crickets are nosier than the frogs, and best of all, the mosquitoes have all but disappeared from our macadamia orchard. If the frogs control the mosquitoes, maybe native birds at lower elevations can be saved from avian malaria.

Michael M. Kraus
Hilo, Hawaii