Fleas are oviparous, and undergo a very complete metamorphosis.
There are many large and poisonous spiders and flies; fleas and mosquitoes abound.
(I) Plague can be carried by fleas from an unhealthy rat.
We may remark that fleas possess no wings, but are understood to possess a true pupa.
It has been previously remarked that the phenomena of holometabolism are connected with the development of wings inside the body (except in the case of the fleas, where there are no wings in the perfect insect).