[Facultative imaginal diapause in Xenopsylla conformis (Siphonaptera) fleas]

The factors favouring the cessation of reproduction in X. conformis are laid in the preimaginal state. The drop in temperature during the formation of imago at the pupal stage is a signal for the cessation of reproduction. Imagos hatched at a temperature lower than that of developmental conditions of preimaginal stages do not start reproduction and enter facultative imaginal diapause state. With further decrease in temperature the state of fleas intensifies. With the rise of temperature fleas come out of diapause. In autumn coming out of diapause begins at a temperature higher than 20 degrees, on the 8th--9th day. The lower air temperature the more rapid is coming out of diapause, at a rise of temperature of 3 to 5 degrees.