摘要：URBAN ECOLOGY IS A RELATIVELY NEW AREA OF RESEARCH, WITH URBAN ECOSYSTEMS BEING DEFINED AS ENVIRONMENTS DOMINATED BY HUMANS. INSECTS AND ARACHNIDS ARE 2 GROUPS THAT SUCCESSFULLY EXPLOIT THE HABITATS OFFERED BY HUMAN HABITATIONS. WE ANALYZED THE OCCURRENCE AND DENSITIES OF SPIDERS FOUND IN HOUSES IN MEXICO CITY. WE USED MATERIAL COLLECTED BETWEEN 1985 AND 2003. WE RECORDED 1 196 SPIDERS FROM 109 HOUSES. THE LIST INCLUDES 25 FAMILIES, 52 GENERA AND 63 SPECIES OF SYNANTHROPIC SPIDERS. INDICES OF OCUPATION, DENSITY AND SEASONALITY, AS WELL AS RANK ANALYSES WERE USED TO MAKE THE FOLLOWING CLASSIFICATION OF SYNANTHROPISM: ACCIDENTAL (DENSITY INDEX 0-0.9), OCCASIONAL (1-2.9), FREQUENT (3.0-9.9) AND COMMON (10 OR MORE). THE SYNANTHROPIC SPIDER FAUNAS OF 5 NEW WORLD COUNTRIES ARE COMPARED.
