Holocnemus pluchei, commonly known as the marbled cellar spider, is a species of Pholcidae, a family commonly referred to as "cellar spiders" or "daddy long-legs". This species is distributed across the North Pacific region of the United States, as well as in parts of North Africa, Europe, and the Mediterranean. It is considered a common household spider and builds its nest in attics, basements, and eaves of houses. Although some members of the species live in solitary webs, the majority join already existing webs and migrate to new webs multiple times throughout the course of their lives. A unique feature of H. pluchei is that while in many species of spiders, stridulation commonly occurs by males during sexual encounters, in H. pluchei, females also possess stridulatory organs, and both sexes engage in stridulation. Description Males and females of the species are approximately the same size, with males ranging between 5–7 mm and females ranging between 5-7.5 mm. H. pluchei have long fragile legs with black and white circles around the joints. Immature members of the species resemble adults. Females have swollen pedipalps that resemble the pedipalps of a male before his final molt. Females also have a sternum projection, which is thought to play an important role in mate selection by improving females’ control over copulation. Both females and males have stridulatory organs of the type where the pedipalp rubs against the chelicera, and no morphological differences in these organs have been observed between the sexes. Phylogeny Holocnemus pluchei belongs to the family Pholcidae, which contains over 1800 species, including multiple types of "daddy long-legs". Within this family, H. pluchei belongs to the genus Holocnemus, which contains just two other species, H. caudatus, found in Spain and Sicily, and H. hispanicus, found in Spain. Habitat and distribution The marbled cellar spider is native to the Mediterranean area of Europe and Northern Africa. It may have been introduced to the North Pacific region of the United States in the mid-1900s. It is now commonly found in Southern California, and is considered an urban pest. It builds its web under rocks, in basements, or on walls of buildings. This species primarily inhabits warm terrain, spaces below rocks, caves, and basement areas. Diet Holocnemus pluchei prey on various species of insects, including fruit flies, houseflies, and damselflies. Some members of the species live in groups, and although this incurs an additional cost of