More challenging than birdwatching and not nearly as popular, insect-watching — noting and sharing exactly what one sees and where — is nevertheless on the rise.

Concern about dwindling native insect populations is one reason why. And new technology has made it easier to log insect sightings and become part of wide-reaching "citizen-scientist" projects.

A worldwide project called "Never Home Alone: The Wild Life of Homes," for example, aims to photograph and catalog the insects, spiders and other tiny creatures that share our homes. It was created by Rob Dunn, author of "Never Home Alone: From...