THE JUVENILE HORMONE. VI. EFFECTS OF THE 'PAPER FACTOR' ON THE GROWTH AND METAMORPHOSIS OF THE BUG, PYRRHOCORIS APTERUS

1. American paper products contain an extractable, heat-stable lipid (PF) with high juvenile hormone activity for the bug, Pyrrhocoris apterus. When reared in contact with "active paper" or extracts prepared front active paper, larval Pyrrhocoris undergo one or more supernumerary larval moults and finally die without completing metamorphosis or attaining sexual maturity.2. As a potent analogue of the juvenile hormone of Pyrrhocoris, PF blocks those aspects of development which can take only in the absence of juvenile hormone—namely, the transformation of the fifth stage larva into an adult. By contrast, it fails to interfere in any way with normal growth and moulting during the first four larval instars—i.e., with developmental events which normally take place in the presence of high levels of endogenous juvenile hormone.3. Sensitivity to PF is maximal at the outset of the final (fifth) larval instar. At this particular stage, metamorphosis is blocked by contact with PF for a period as brief as one hour. ...