Functional Value of Matriphagy in the Spider Amaurobius ferox

The adaptive value of matriphagy, the consumption of the mother by her offspring, in the sub-social spider Amaurobius ferox (Araneae, Amaurobiidae) was experimentally evaluated in terms of the benefits to the offspring and the costs to the mother. Matriphagy resulted in a 2.5-fold weight gain in the offspring over their initial weight, advancement of their moulting time, and larger body mass at dispersal in comparison with clutches deprived of matriphagy, but otherwise well provisioned with prey. Matriphagous offspring were also more successful at capturing large prey items, had a more extended social period, and a higher survival rate at dispersal. Mothers separated from their broods just prior to matriphagy were able to produce second clutches, effectively producing 33% more viable offspring (compared with the first clutches). However, the estimated reproductive outputs of the alternative maternal strategies (being devoted to the first clutch vs. deserting the first and producing a second one) suggest that mothers of A. ferox that are cannibalized by their broods enjoy greater reproductive success than those that escape cannibalism and produce second clutches.