Adult fleas can survive without a blood meal for about 1–2 weeks under normal room temperature conditions (20–25 °C).
At lower temperatures (10–15 °C), their metabolism slows down, and survival time can extend to several weeks.
The starvation resistance of flea pupae far exceeds that of adults — pupae can survive for months without a host.
The pupa can sense environmental vibrations, temperature, and carbon dioxide concentration; when these signals indicate "a host is nearby," the pupa can emerge as an adult within seconds and jump onto the host — this is why a long-vacant house can suddenly have a flea outbreak when new occupants move in.
Although the starvation resistance of fleas is not as extreme as bed bugs (which can survive over a year), their "standby" capability in the pupal stage gives them astonishing persistence in vacant environments.
If you are moving into a house that has been vacant for several months and previously housed pets, you should conduct a thorough environmental treatment before moving in — comprehensive vacuuming, steam cleaning of carpets and sofas, and if necessary, application of an IGR-containing spray.