The blood/germ cell barrier in male Schistocerca gregaria: the time of its establishment and factors affecting its formation.

Tracer studies carried out on the testes of the insect Schistocerca gregaria demonstrate a blood/germ cell barrier which is established prior to the onset of meiosis in the 3rd instar. Ecdysterone treatment in vitro prematurely stimulates the formation of the barrier in the testicular follicles of 2nd instar hoppers; this effect is antagonized by juvenile hormone. The follicles may be a store for the barrier-stimulating factor because testis extract also induces premature production of the barrier.