Molecular phylogenetics is a branch of phylogenetic analyzes of kinship differences at the molecular level, largely considering the DNA and RNA sequences, in order to obtain information about the evolutionary relationship of organisms and their evolutionary history. The purpose of the molecular phylogeny is to draw design a phylogenetic tree of the collected data set of sequences of genes known as molecular markers. The objective of this paper is to describe an example of the procedure of a study in molecular phylogenetics. In this paper, the procedure is described by how to prove a new species of cave spiders - Nesticus baeticus López-Pancorbo & Ribera, 2011 and its comparison in phylogeny with the other species of the genus Nesticus that are endemic to the area of the Iberian Peninsula. To create a tree they used the method of Maximum parsimony where they used a species form the genus Nesticus which is located in China as an outgroup and with the bootstrap test they checked the reliability of each node. In the final analysis of the tree, they came to the conclusion that all the species from genus Nesticus located on the Iberian Peninsula are not within the same monophyletic group and it is assumed that they colonized the Iberian Peninsula independently three times. To confirm or reject the hypothesis, the future research should be focused on resolving the philogeny of the Mediterranean Nesticidae and will include most of the Mediterranean species to test the molophyletic status of current genera.