Matriphagy
[1][2] The behavior generally takes place within the first few weeks of life and has been documented in some species of insects, nematode worms, pseudoscorpions, and other arachnids as well as in caecilian amphibians.
However, the process is best-described in the Desert spider, Stegodyphus lineatus, where the mother harbors nutritional resources for her young through food consumption.
In some species, matriphagous offspring were also more successful at capturing large prey items and had a higher survival rate at dispersal.
These benefits to offspring outweigh the cost of survival to the mothers and help ensure that her genetic traits are passed to the next generation, thus perpetuating the behavior.
The uniqueness of this phenomenon has led to several expanded analogies in human culture and contributed to the pervasive fear of spiders throughout society.
[12] Matriphagy commences days later when the mother begins communicating with her offspring through web vibrations, drumming, and jumping.
[12] Mothers of one particular Australian species of the crab spider, Australomisidia ergandros (formerly in genus Diaea), are only able to lay one clutch, unlike the Black lace-weaver.
[9] They invest a significant amount of time and energy into storing nutrients and food into large oocytes, known as trophic eggs, similar to the Black lace-weaver.
[9] Right after hatching, the hatchlings of the desert spider Stegodyphus lineatus rely solely upon their mother to provide them with food and nutrients.
Meanwhile, her midgut tissues continue to degrade into a liquid state to maximize the amount of nutrients from the mother's body that her offspring will be able to obtain.
[14][15] This is mainly for the purpose of avoiding predation and maximizing their offspring's survival, since females are unable to produce a second clutch.
[2] Functionally analyzing matriphagy in this manner sheds light on why this unusual and extreme form of care has evolved and been selected for.
However, in some species such as the Funnel-web spider Coelotes terrestris, matriphagy is only observed under certain conditions and extended maternal protection is the main method by which offspring receive care.
In other organisms such as the African social velvet spider, Stegodyphus mimosarum and Caecilian amphibians, parental behavior closely related in form and function to matriphagy is used.
In addition, the mother can keep feeding while guarding her progeny without any weight loss, allowing her to collect sufficient food for both herself and her offspring.
This suggests that matriphagy can exist under nutrient-limited conditions, but the costs generally outweigh the benefits when mothers have sufficient access to resources.
The offspring are born with specific dentition that they can use to peel and eat the outer epidermal layer of their mother's skin.
[19] Viviparous (developing in the mother) caecilians on the other hand, have specialized fetal dentition which can be used for scraping lipid-rich secretions and cellular materials from the maternal oviduct lining.
Offspring suck nutrients primarily from the dorsal part of the adult female's abdomen, and she may still be alive during this process.
[20] This behavior is not quite the same as matriphagy because Stegodyphus spiderlings are perfectly tolerant to other offspring, healthy conspecifics, and members of other species, suggesting that ordinary cannibalism is suppressed.
[20] Those who have been exposed to matriphagy may be frightened by such a seemingly strange and bizarre natural behavior, especially since it is mainly observed in already feared organisms.
Altruism in this case refers to an "intentional action ultimately for the welfare of others that entails at least the possibility of either no benefit or a loss to the actor," and is a highly popularized and desirable concept in many human cultures.
[11] Although participation in matriphagy is not truly an intentional action, mothers are nevertheless driven by natural selection pressures based on offspring fitness to engage in such behavior.
