Oenothera flowers are
pollinated by insects, such as
moths and
bees. Like many other members of the Onagraceae, however, the
pollen grains are loosely held together by
viscin threads, so only insects that are
morphologically specialized to gather this pollen can effectively pollinate the flowers. Bees with typical
scopa cannot hold it. Also, the flowers open at a time when most bee species are inactive, so the bees which visit
Oenothera are generally
vespertine temporal specialists: bees that forage in the evening. The
seeds ripen from late summer to fall.
Oenothera are used as food plants by the
larvae of some
Lepidoptera species, including the large white-lined sphinx (
Hyles lineata). The flower moths
Schinia felicitata and
S. florida both feed exclusively on the genus, and the former is limited to
O. deltoides. In the wild, some species of evening primrose act as
primary colonizers, quickly appearing in recently cleared areas. They germinate in
disturbed soils, and can be found in habitat types such as
dunes, roadsides, railway embankments, and waste areas. They are often casual and are eventually out competed by other species. Based on observations of evening primroses (
O. drummondii), a study discovered that within minutes of sensing the sound waves of nearby bee wings through flower petals, the concentration of the sugar in the plant's nectar was increased by an average of 20 percent. Experiments were also conducted on flowers with the petals removed. No change in nectar production was noted, indicating that it is indeed the petals that sense sound. ==Origin==