OSCILLATORY CONTRACTILE MECHANISM OF INSECT FLIGHT MUSCLE.

The flight muscles of gian water bugs provide the best material for a study of the peculiar properties of insect fibrillar muscle. Although little was previously known about the biology of these insect, three species, Lethocerus maximus, L. annulipes and B. Malkini have now been extensively studied in the field in Trinidad and the techniques for breeding L. maximus and B. malkini worked out. Against the background of studies carried out in Oxford in the last four years Pringle, 1967 special attention was given to the biochemistry of the ATPase activity of actomyosin and myofibrils prepared from fibrillar flight muscles Maruyama and Allen, 1967 Maruyama, Pringle and Tregear, in press. This enzyme is similar to that from vertebrate muscle in its sensitivity to ionic strength and its requirements for MgATP as substrate but its dependence on the concentration of Ca2 is different and this is related to the stretch activation shown by intact glycerinated muscle preparations Ruegg and Tregear, 1966. Previous studies Chaplain, 1966 suggested an important role for ADP in the control of ATPase activity of insect actomyosin. Further studies show that the ionic strength of the medium has an important effect on the inhibition or activation produced by ADP Maruyama and Pringle, 1967. Author