Plant their larval host plants and inspect the vegetation to search out and determine them in late spring and summer time. Then create a terrarium and feed them fresh leaves of their host plant day by day. Parsley, fennel, and dill work nicely for feeding jap black swallowtails. A healthy backyard, like all ecosystem, is a matter of balance, and gardeners should be taught to tolerate some insect activity. A various garden rich in native vegetation and insects regulates itself and is better able to stand as much as herbivory. Leafhoppers, scales, thrips, and aphids are pure and needed components of the ecosystem.