Do Spiders Give Milk?
WouterIf you are curious about the mysterious world of spiders, you may wonder, do spiders give milk? The answer is yes. Several species produce milk for their offspring, and a new study suggests the specialized secretion is actually a form of maternal care.
A study of a jumping spider published by the Chinese Academy of Sciences in the journal Science indicates that females give their offspring a milk-like substance. This may be a form of parental care that equips the spider for survival in a competitive environment.
Researchers also found that the survival rate of young spiderlings was higher when they were allowed to feed on their mother’s milk for the first 20 days of their lives. However, once these youngsters started hunting for food, milk became a less important source of nutrition. In these experiments, the survivors were about 50 percent more likely to survive than the young that did not receive any milk for the first 20 days.
Some invertebrates, such as cockroaches and earwigs, also produce a milk-like fluid. These fluids contain fat and protein, just like mammalian milk. They are often used by developing embryos in cockroaches and birds, respectively.
However, other spiders do not produce milk. One of these species, Toxeus magnus, is a ant-like spider that does not use mammary glands to produce milk. Its offspring consume a mixture of its own milk and insects.
The unusual behavior of Toxeus magnus is similar to the behavior of some other invertebrates, but researchers have not yet identified the same gland in other non-mammals. Whether this behavior reflects a genetic predisposition or an evolutionary response to predation risk remains unknown.
