This is one of an amazing sequence photographed by Pavel Krásensky …
Strepsiptera or Twisted-wing parasites are a bizarre internal parasites of bees and wasps. Their life-cycle begins similar to the oil beetles (Meloidae).
From NC State University Entomology pages:
Strepsiptera share so many characteristics with beetles that some entomologists classify them as a superfamily of Coleoptera. In fact, Strepsiptera and certain parasitic beetles (in the families Meloidaeand Rhipiphoridae) are among the very few insects that undergo hypermetamorphosis, an unusual type of holometabolous development in which the larvae change body form as they mature. Upon emerging from their mother’s body, the young larvae, called triunguloids, have six legs and crawl around in search of a suitable host. In species that parasitize bees or wasps, a triunguloid usually climbs to the top of a flower and waits for a pollinator. When a host arrives, the larva jumps aboard, burrows into its body, and quickly molts into a second stage that has no distinct head, legs, antennae or other insect-like features. These larvae grow and continue to molt inside the host’s body cavity, assimilating nutrients from the blood and non-vital tissues. After pupating in the host, winged males emerge and fly in search of mates. An adult female remains inside her host, managing to attract and mate with a male while only a small portion of her body protrudes from the host’s abdomen. Embryos develop within the female’s body, and a new generation of triunguloid larvae begin their life cycle by escaping through a brood passage on the underside of her body.
See the whole sequence at Pavel’s blog, Macrophotography (use Google translate!). My Meloidae post can be seen at The Black Oil Beetle.