Parent-offspring relationships take many forms. One particular form of parental behaviour is egg care when parents brood their eggs after laying them. Parents of many oviparous vertebrates and terrestrial arthropods brood their eggs. Spiders present a particular interesting form of parental behaviour, enclosing their eggs in a silk sac (or egg-sac) and can care for it until spiderlings emerge. This study investigated proximal cues which stimulate the wolf spider Pardosa saltans (Lycosidae) to care for their egg-sacs, transport it for 30 days and open it to allow spiderlings to emerge. We showed that mothers discriminate between egg-sacs differencing in mass (empty or not) as they do not hang an empty egg-sac but do not discriminate between egg-sacs with viable and nonviable juveniles either when manipulating or when hanging them. However, mothers do not open nonviable egg-sacs but abandon them only at the end of the juvenile development period when spiderlings are due to emerge (30-day-old egg-sacs). We investigated egg-sac silk chemical cues that mothers detected by presenting them egg-sacs washed with different polar solvents or chemical egg-sacs silk extracts. We identified the polar and apolar chemical compounds of lipid extracts of egg-sacs detected by mothers during manipulation. Our results demonstrate that these compounds stimulate maternal care, and mothers detect mobility of juveniles at the end of the post-embryonic period, when juveniles are ready to emerge from a 30-day-old egg-sac indicating that tactochemical stimuli are involved in egg-sac care.

Data_Figure_3Data of the first experiment.Data_Figure_4Data of the second experiment.