A reason for this unusual abundance was broached by Dr. Paul Opler, a superb lepidopterist who lives in Ft. Last year was a case study in unfavorable conditions, with the April freeze killing all the ash new growth and hot, dry weather following this. Likely, many of the insects went into diapause rather than continuing to develop so that we now have many swallowtails that came out a year later than normal, supplementing those that underwent normal development cycles. Adults of these insects feed on nectar. Larvae develop as unusual caterpillars that you may soon observe on plants.
Young stages are usually black and white with a shiny sheen, resembling a bird dropping.
Watch for the larvae. Those of the two-tailed swallowtail can be found most commonly on chokecherry, wild plum or ash. Larvae of the western tiger swallowtail are most common on plum, wild cherries, hawthorn, poplars and willow. NPTN will soon become available on the Internet. Where trade names are used, no discrimination is intended, and no endorsement by the cooperative extension service is implied.