The title is a term from moral theology — delectación morosa is the pleasurable lingering over a delightful thought — and Lugones uses it with all the mischief of modernismo. The sonnet paints an evening in a garden: the dusk laid on with a light brushstroke, the moon coming up, and two lovers whose scene is hinted among the flowers and the shade.
Lugones here is a painter in words: every line is colour and scent, and the sense arrives through the senses before the idea. It belongs to Los crepúsculos del jardín (1905), the most sensual book of Argentine modernismo, where the garden is not a backdrop but the very stage of desire.
The verse is kept in Spanish. Translating it in passing would replace the work with a paraphrase of it.