Figure 3.

Developmental trajectory of the flight apparatus (wings and flight muscle) in Acyrthosiphon pisum. Four developmental pathways and two developmental switches are hypothesized: the normal flight apparatus formation pathway is seen in wing and flight muscle primordia in winged males and viviparous females; the developmental suppression pathway is seen in flight muscle development of wingless males; the primordia degeneration pathway is seen in wing and flight muscle primordia development in wingless viviparous females and wing primordia development in wingless males; the no primordia formation pathway is seen in wing and flight muscle primordia development in fundatricies and oviparous females. Two developmental switches regulate primordia formation per se and the developmental fate of once-formed primordia, respectively. FA, flight apparatus.