[Hormonal stimulation and in vitro cellular differentiation in the integument of the desert locust Schistocerca gregaria (author's transl)].

Spontaneous cellular differentiation (glandular units appearance with a well-defined duct) is observed in larval integument of Schistocerca cultured in an hormone free medium. Hormonal stimulations modify the expression of this phenomenon, particularly the frequency of new elaborated duct cells belonging to secretory units. The most effective factor is supplied by the prothoracic glands. Complete secretory units can be observed but the glandular cells are in an undifferentiated and unfunctional state. They appear active if the corpora allata act after the prothoracic glands. Corpora allata alone or synthetic juvenile hormones have an inhibitory effect. The addition of alpha-ecdysone permits only cellular divisions, a preliminary and indispensable condition for ulterior differentiation. Between cuticles deposited with beta-ecdysone, new formed ducts take place in the theorical imaginal exuvia. These observations prove that the elaboration and the activity of imaginal glandular units are conditioned by the larval hormonal context: by contrast, sex dimorphism is only a genetic dependant process.