Population dynamics of Loxosceles similis (Moenkhaus, 1898) in a brazilian dry cave: a new method for evaluation of population size

Resumo

Variation in population size, distribution and displacement in the cave, age structure and sex ratio of a cave population of Loxosceles similis (Moenklaus, 1898) was studied in a southeastern limestone Brazilian cave. Spider abundance was smaller in July, 1998 (n=863) and higher in
January, 1999 (n=1420), fact that can be related with an eventual increase of prey number in the rainy season. The abundance of spiders decreases from the entrance to the cave deep. Some individuals had dislocated at
least 40 meters in one week. Some authors consider the mobility of 2 meters as expressive for species in this genera. The operational sex ratio was 1:6, but it changed during the study period. The population sizes were estimated by a new method here proposed.