Egg sac recognition and fostering in the wolf spider Pardosa milvina (araneae: lycosidae) and its effects on spiderling survival.

Many animals provide parental care to increase the success of offspring. Parental behaviors can be costly, and should only be directed toward related young. Offspring recognition and differential effort are ways that animals ensure that care is directed toward related individuals. Pardosa milvina is a small wolf spider that provides parental care for their young, carrying first their egg sac and later their spiderlings. This species is known to pick up abandoned egg sacs. We conducted a study to determine whether female P. milvina differentiated between her own egg sac and a conspecific's egg sac and whether there was a benefit to spiderlings in being raised by their biological mother, and whether age, when removed from the mother, influenced the outcome. In one experiment, we removed the egg sac from a female and gave her a choice of items to reattach: their own egg sac, another spider's egg sac, or a plastic bead. Females were more likely to pick up their own egg sac than another spider's. In another experiment, we removed a female spider's egg sac either 1 day or 7 days after the eggs were produced and gave them either their own egg sac or another spider's egg sac to care for. We measured hatching success and offspring survival. Spiders manipulated after 7 days were more likely to be abandoned as eggs, whether cared for by their biological mother, and reached adulthood less often. However, cross‐fostering had no effect on spiderling success whether the transfer occurred after 1 day. Our data showed that P. milvina can recognize their own egg sac, but there was no evidence of differential parental care provided to the biological offspring. [ABSTRACT FROM AUTHOR]