Expansion of native junipers, Juniperus Linnaeus (Cupressaceae), is altering landscapes in the western U.S., prompting extensive management efforts to counter this spread and the negative effects on impacted ecosystems. Our studies investigating sources of seed mortality in western juniper, Juniperus occidentalis Hooker; Utah juniper, Juniperus osteosperma (Torrey) Little); and California juniper, Juniperus californica Carrière, have revealed a number of previously unreported seed-attacking arthropods. One of the most commonly encountered insects at collection sites in California and Nevada are cone-boring cosmet moths (Cosmopterigidae) in the genus Periploca Braun, 1919. DNA analysis of insect adults and immatures both reared and dissected from juniper berries definitively associated Periploca adults with their immature stages and with seed damage while also screening for parasitoid DNA to reveal parasitoid-host relationships. Sequence data for Periploca adults and larvae revealed the presence of three species of Periploca attacking juniper berries at our survey locations. These have been identified as P. atrataHodges, 1962, commonly referred to as the juniper cone moth, along with P. juniperiHodges, 1978, and P. serrulataHodges, 1978. Previously unreported details regarding the life histories of these three species of Periploca, all of which were encountered in western, Utah, and California juniper, were revealed. In addition, berry dissections, rearing efforts, and DNA sequence data have linked numerous parasitoids to juniper berry-infesting Periploca. These findings develop a more refined understanding of the genus Periploca and the arthropod community infiuencing juniper seed production, which can provide potentially valuable tools for the ongoing management of juniper expansion.