The armored spider Monoblemma muchmorei Shear 1978 occurs in the wet subtropical forest of the Caribbean National Forest, Luquillo, Puerto Rico. It is found almost entirely in bamboo litter between 100 and 110 m in elevation and shares this habitat with a number of other species of spiders, ants and other small arthropods. The two sexes come together with no evidence of prior courtship, mate, and may remain in copula for many hours. A small decorated egg sac is produced with only one egg in each sac. The female tends the unusually large spiderling for a week or more and appears to offer some protection from other small invertebrates. For reasons not understood, second instar spiders suffered a high mortality rate, up to 70%. In captivity, the adults may live for eight months or more. Observations on the predator-prey interactions among M. muchmorei and other small invertebrates are reported. At least 30 species of spiders in 16 families are found associated with M. muchmorei in the bamboo litter.