No, they are not the animal equivalent of Yummy Mummies like Victoria Beckham and the soon- to- be one– Kate Middleton, but rather they are LITERALLY yummy mummies to their babies.
Yes, matriphagy is the consumption of the mother by her offspring. And this extreme act of animal altruism exists amongst certain types of spiders and today I am going to share with you the maternal suicidal tendency of black-lace weaver mothers.
Most spiders are solitary animals and that it is a rare for parent spiders to invest in the care of their young. But the black-lace weaver mothers and some of their cousins are sub-social, they live together in communal webs at certain phases of their life, constructing nests, caring and feeding their young. (Salomon, Schneider, & Lubin, 2005)
Black-lace weaver spiders (Amaurobius ferox) can be found under stones and logs in the woodlands and gardens of Europe and North America.
The female Amaurobius ferox spider produces a single clutch of 60-130 spiderlings, which she feeds by laying eggs for her offspring to eat. The black-lace weaver moms do more than providing food; they voluntarily offer their bodies up for their babies to devour. While this extreme sacrifice might seem illogical to the human mind, it is very much justified in science.
According to South Korean scientist, Dr Kil Won Kim of the University of Incheon of the Republic of Korea, his study of the cannibalistic behavior of baby spiders Amaurobius ferox revealed that the pros of matriphagy (to the offspring) outweighs the costs (to mother black lace-weaver spiders). (Kim, Roland, & Horel, 2000)
The advantages conferred to spiderlings in cannibalizing their mom are as follows-
- Overall weight gain in offspring ( Yes, fat babies are always desirable) and thus larger body mass when they finally disperse
- Their development is sped up as seen in the advancement of their moulting time
- By being the big fat kids, their chance of capturing large prey items and at surviving after dispersal is also much higher
However, even if the mother black-lace weaver spider is not cannibalized (removed by the scientists before matriphagy) and is ultimately allowed to produce a second clutch , the study has shown that both clutches of spiderlings, in general, suffer from reduced abilities of surviving and prey-subduing after leaving the maternal nest.
Hence, a semelparous strategy (i.e. matriphagy and being devoted only to the first brood) has been found to produce a higher number of surviving offspring, as opposed to abandoning them early to lay a second clutch.
Link to video of spiderlings devouring their mother- http://news.bbc.co.uk/earth/hi/earth_news/newsid_8757000/8757771.stm
“After she has died, the spiderlings then form a social group for 3-4 weeks until they disperse from the social nest. During this time, the spiderlings are known to cooperate by going hunting together. By cooperating on a hunt, the spiderlings are capable of attacking and subduing prey up to 20 times bigger than themselves”. (Walker, 2010)
Like what royal yummy mummy Diana, Princess of Wales has remarked, “A mother’s arms are more comforting than anyone else’s.” I guess it is the case for black-lace weaver spiderlings.
And Happy Mothers’ Day!
Kim, K. W., Roland, C., & Horel, A. (2000). Functional Value of Matriphagy in the Spider Amaurobius ferox. Ethology, 106, 729-742.
Salomon, M., Schneider, J., & Lubin, Y. (2005). Maternal investment in a spider with suicidal maternal care, Stegodyphus lineatus (Araneae, Eresidae). OIKOS, 109, 614-622.
Walker, M. (2010, June 24). Baby cannibal spider gang makes web vibrate in time. Retrieved April 02, 2013, from BBC Earth news: http://news.bbc.co.uk/earth/hi/earth_news/newsid_8757000/8757771.stm