Fleas are typical holometabolous insects. The life cycle of any flea species consists of an egg that hatches into a larva, which generally undergoes three larval moults and an inactive pupal stage before emerging as an adult. Although Siphonaptera is a small order, fleas demonstrate high variability in some life-cycle details such as diversity of larval microenvironmental preferences, larval feeding mechanisms, and nutritional requirements. In this chapter, I present some information on flea life cycles.

Mating and oviposition

Newly emerged female fleas have underdeveloped ovaries blocked with a follicular plug (Kunitskaya, 1960, 1970; Vashchenok, 1966a), whereas newly emerged males of many species have a testicular plug which prevents the passage of sperm from the testes to the vas deferens (Akin, 1984; Dean & Meola, 1997). In general, the blood meal is a trigger for the development of ovaries in female fleas (Vashchenok, 1988; Liao & Lin, 1993) and for the dissolution of the testicular plug in males (Rothschild et al., 1970; Kamala Bai & Prasad, 1979; Akin, 1984). Consequently, the majority of fleas mate after feeding. This was established, for example, for Leptopsylla segnis and Leptopsylla taschenbergi (Kosminsky, 1960) and Citellophilus tesquorum (Bryukhanova, 1966). Unfed Nosopsyllus fasciatus usually do not mate, but can be forced to copulate by increased air temperature (Iqbal & Humphries, 1970). Occasionally, only one sex has to be fed prior to copulation (e.g. Echidnophaga gallinacea: Suter, 1964; Marshall, 1981a). However, some species can mate immediately after emergence or, at least, prior to the first blood meal.