Clubiona pacifica Banks, 1896 is a common secondary occupant of lepidopteran leafrolls on alders (Alnus spp.). We collected rolled alder leaves at riparian sites in Washington State to determine seasonal phenology of C. pacifica and to examine egg laying and predatory activity. All stages of the spider occurred in rolled leaves, and spiders were found in rolled leaves throughout the season. Rolled alder leaves were used by C. pacifica as protected sites in which to molt and spend inactive periods and possibly to seek prey. Field observations and greenhouse experiments indicated that C. pacifica is capable of preying upon leafroller larvae. Occasionally, lepidopteran leafrolls were used by C. pacifica as ready-made chambers in which to oviposit, but more commonly the female spider herself folded an alder leaf to form a protective retreat for oviposition. These egg sac retreats and the associated egg sac are described and illustrated. After eclosion C. pacifica passes through a prelarval stage, a larval stage, and six nymphal stages before reaching adulthood. The principal period of reproduction and egg deposition is June and July, and most post-larval stages of C. pacifica appear to overwinter. We postulate that some individuals require two years to complete their life cycle although others may do so in a shorter time. Three ichneumonid wasps parasitized C. pacifica: Gelis sp. attacked the eggs; Schizopyga frigida and Zaglyptus varipes parasitized immature and adult spiders.