First and 2nd instars of Stomopteryx palpilineella (Chambers) feed typically as leafminers and 3rd and 4th instars as leaftiers of the legume crownvetch, Coronilla varia L., in Pennsylvania. Adults emerge in late April to early May. Weekly sampling of all mines and tied leaflets on the terminal 6 in. of 50 stems from May to November 1973 indicated that there are 3 complete generations a year. A 4th generation overwinters as 3rd and 4th instars within tied leaflets. Information is given on adult longevity, fecundity, developmental times of the immature stages, and distribution; detailed observations on mining and tying behavior are also presented. Although 3rd generation larvae caused heavy leaf drop in a highway planting of crownvetch, no economic damage was attributed to this moth in 3 commercial forage fields. Larvae were found infrequently on other legumes, and laboratory studies indicated that alfalfa is not a suitable host plant. Five species of parasitic Hymenoptera, including 2 of Braconidae and 3 of Eulophidae, are associated with this species. The egg, 4th instar, and pupa are described and illustrated.