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Three groups of spiders were raised from birth in the laboratory: Lycosa thorelli, L. carbonelli, and their experimentally obtained hybrid progeny. We analyzed the behaviour of the three male groups in the presence of a hybrid sexual pheromone. From the tests, 22 behaviour units were identified; 11 were simple and 11 were complex, the latter resulting from temporal overlapping of two or three simple units. Hybrid males showed behaviours similar to those of each of the parental species, but their characteristics were mainly intermediate between the two species. Variability in sexual behaviour of the hybrids was similar to that of parental males. Parental males exposed to a hybrid stimulus showed an activity level intermediate to previous descriptions of sexual behaviour elicited by conspecific and heterospecific stimuli. The importance of certain visual and acoustic displays for reproductive isolation, and their possible inheritance mechanisms, are a particular focus of discussion.

The S-type vocalizations of three populations of Ctenomys from Uruguay were compared: two of Ctenomys pearsoni Lessa and Langguth, 1983 from Penino and Relincho and the third from a different karyomorph of the genus (Solís karyomorph). Ten rhythm and 3 frequency variables were used for discriminant analysis. The results showed that a set of nine variables allowed a complete separation of the populations. The two C. pearsoni populations were correctly discriminated from one another using four variables, the differences lying especially in the rhythm domain. Information about the general biology and distribution of the animals suggest that these differences could be explained as a product of chance variations and later fixation of the variants in local populations. The Solís karyomorph was also correctly discriminated from the other populations using four variables, but main frequency seems to play an important role in this case.Sección Etología,

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Here we discuss different factors that could influence the development of vocal and/or seismic communicative channels in subterranean rodents. We suggest that: 1) Highly social subterranean rodents that do not leave their burrows use essentially vocal signals in the vibrational channel; 2) Solitary and almost permanently fossorial species use vocal signals in short range and seismic signals in long range communication; 3) Other solitary species that leave the burrow system more frequently and that retain good visual capabilities are constrained to use vocal communication only. Also we suggest that seismic communication probably derives from digging activities and, consequently, developed after the acquisition of the subterranean way of life. The first three statements are based on a previously proposed relationship between visual capabilities, hearing capabilities, time spent outside the burrows, social organization and type of vibrational signals used by the species. The fourth statement is based in the correlation found between digging and transporting tools and thumping tools, that are the same across the literature on pertinent genera. Some thumping techniques unique to subterranean animals lead us to propose an evolutionary sequence leading from digging to thumping.

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