Its round or slightly elongated stems usually form small, dense clusters, and flowers are commonly born alongside fruit.

Miller named it Cactus proliferus, "commonly called Small Childing Melon-Thistle".

[7] It was originally described by Miller as a "roundish prolific Cactus, with oval tubercles closely joined, having long white beards" and "tufts of white down on the knobs, and also between them at every joint, which makes the whole plant appear as if it was covered with fine cotton".

[2] It usually grows in dense clusters, with each stem being round to slightly elongated, reaching about 9 tall and 4.5 cm wide.

It has many radial spines—around 60 or more—that are white, bristle-like to fine and hair-like, and can be straight or twisted, ranging from 6 to 15 mm long.

These spines are slightly fuzzy, glassy white to pale straw-yellow at the base, and have darker tips, measuring 4 to 7 mm long.

[1][6] Its flowers are cream yellow with a reddish brown midstripe, approximately 15 mm long and just as wide.

arachnoidea is set apart from the other subspecies primarily by the smaller size of its stems and an overall softer appearance.

It has over 50 thin, needle-like radial spines per areola; these are 5-9 mm long and white.

[2] Mammillaria prolifera is native to Texas, northeastern states of Mexico, Cuba, and Hispaniola.

prolifera is found in Cuba, Dominican Republic, and Haiti,[1] typically at elevations between 30 m and 50 m above sea level.

[10] Specific locations include Port-au-Prince and Ganthier in Haiti and Guayubin in the Dominican Republic.

arachnoidea has been collected in the Mexican states of Hidalgo (in the canyon of the Moctezuma River, east of Jacala) and Tamaulipas (8 km west of Antiguo Morelos, on rocks next to Federal Highway 8) at 300 meters above sea level.

[8][6] In Texas it is found at 0-600 m in the Tamaulipan thorn scrub, oak-juniper woodlands, gravel, limestone crevices, or litter beneath vegetation, cliffs, hills, valleys, and plains.

Here it thrives in rich, deep lowland soils near thickets or among the clumps of coastal grasses on the flat plains near the Gulf.

At Eagle Pass it diverges from the river, and it is found on the rocky hilltops of the Edwards Escarpment, wedged into limestone crevices, often in very little soil and shaded by the rocks.

[6] The ecologist Den Weniger, who observed the two forms in the wild, suggests that they might be phenotypes of the same variable population.

[2] It is appreciated for its attractively dense tufts of spines and its ability to produce flowers and fruit simultaneously and more abundantly than any other Mammillaria species.

gracilis, M. prolifera is easy to propagate and distribute; Pilbeam estimates that most cacti fanciers become interested in the genus after growing these two species.